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* Parallelize correlated subqueries that execute within each worker
@ 2021-05-07 16:30 James Coleman <[email protected]>
0 siblings, 2 replies; 35+ messages in thread
From: James Coleman @ 2021-05-07 16:30 UTC (permalink / raw)
To: pgsql-hackers; +Cc: Amit Kapila <[email protected]>
In a bug report back in November [1] a subthread explored why parallel
query is excluded any time we have "Plan nodes which reference a
correlated SubPlan". Amit's understanding was that the reasoning had
to do with inability to easily pass (potentially variable length)
Param values between workers.
However a decent-sized subset of this kind of query doesn't actually
require that we communicate between workers. If the Subplan executes
per-tuple within the worker then there's no reason I can see why it
needs to be marked parallel unsafe. Amit concurred but noted that
identifying that subset of plans is the difficult part (as is usually
the case!)
At the time I'd started work on an approach to handle this case and
hoped to "post about it in a new thread later this week." That didn't
happen, but here we are now, and I finally have this patch cleaned up
enough to share.
The basic idea is that we need to track (both on nodes and relations)
not only whether that node or rel is parallel safe but also whether
it's parallel safe assuming params are rechecked in the using context.
That allows us to delay making a final decision until we have
sufficient context to conclude that a given usage of a Param is
actually parallel safe or unsafe.
The first patch in this series was previously posted in the thread
"Consider parallel for lateral subqueries with limit" [2] and is
required as a precursor for various test cases to work here.
The second patch implements the core of the series. It results in
parallel query being possible for subplans that execute entirely
within the context of a parallel worker for cases where that subplan
is in the target, a LATERAL JOIN, or the WHERE and ORDER BY clauses.
The final patch notes several places where we set e.g.
rel->consider_parallel but setting the corresponding new value
rel->consider_parallel_recheckng_params wasn't yet necessary. It shows
opportunity either for further improvement or concluding certain cases
can't benefit and should be left unchanged.
James
1: https://www.postgresql.org/message-id/CAAaqYe_vihKjc%2B8LuQa49EHW4%2BKfefb3wHqPYFnCuUqozo%2BLFg%40ma...
2: https://www.postgresql.org/message-id/flat/CAAaqYe_HEkmLwf_1iEHxXwQOWiRyiFd%3DuOu6kwj3sWYdVd1-zA%40m...
Attachments:
[application/octet-stream] v1-0003-Other-places-to-consider-for-completeness.patch (5.1K, ../../CAAaqYe_x1u3V4uPiv=dJ=k2EJ7txhdq6yexJDkYZ1x1pu0QwcQ@mail.gmail.com/2-v1-0003-Other-places-to-consider-for-completeness.patch)
download | inline diff:
From ac93b6513dfd3fd066cbbe51eced2bc00146f0c0 Mon Sep 17 00:00:00 2001
From: jcoleman <[email protected]>
Date: Fri, 7 May 2021 15:37:22 +0000
Subject: [PATCH v1 3/3] Other places to consider for completeness
---
src/backend/optimizer/path/allpaths.c | 4 ++++
src/backend/optimizer/plan/planmain.c | 2 +-
src/backend/optimizer/plan/planner.c | 3 +++
src/backend/optimizer/plan/subselect.c | 3 +++
src/backend/optimizer/prep/prepunion.c | 2 ++
5 files changed, 13 insertions(+), 1 deletion(-)
diff --git a/src/backend/optimizer/path/allpaths.c b/src/backend/optimizer/path/allpaths.c
index ae744da135..5696a54b18 100644
--- a/src/backend/optimizer/path/allpaths.c
+++ b/src/backend/optimizer/path/allpaths.c
@@ -1142,6 +1142,8 @@ set_append_rel_size(PlannerInfo *root, RelOptInfo *rel,
*/
if (!childrel->consider_parallel)
rel->consider_parallel = false;
+ if (!childrel->consider_parallel_rechecking_params)
+ rel->consider_parallel_rechecking_params = false;
/*
* Accumulate size information from each live child.
@@ -1263,6 +1265,8 @@ set_append_rel_pathlist(PlannerInfo *root, RelOptInfo *rel,
*/
if (!rel->consider_parallel)
childrel->consider_parallel = false;
+ if (!childrel->consider_parallel_rechecking_params)
+ rel->consider_parallel_rechecking_params = false;
/*
* Compute the child's access paths.
diff --git a/src/backend/optimizer/plan/planmain.c b/src/backend/optimizer/plan/planmain.c
index bdbce2b87d..5135f9ee97 100644
--- a/src/backend/optimizer/plan/planmain.c
+++ b/src/backend/optimizer/plan/planmain.c
@@ -119,7 +119,7 @@ query_planner(PlannerInfo *root,
if (root->glob->parallelModeOK &&
force_parallel_mode != FORCE_PARALLEL_OFF)
final_rel->consider_parallel =
- is_parallel_safe(root, parse->jointree->quals, NULL);
+ is_parallel_safe(root, parse->jointree->quals, &final_rel->consider_parallel_rechecking_params);
/*
* The only path for it is a trivial Result path. We cheat a
diff --git a/src/backend/optimizer/plan/planner.c b/src/backend/optimizer/plan/planner.c
index 28b8f7d8b5..fb35cd78d1 100644
--- a/src/backend/optimizer/plan/planner.c
+++ b/src/backend/optimizer/plan/planner.c
@@ -4088,6 +4088,7 @@ create_window_paths(PlannerInfo *root,
if (input_rel->consider_parallel && output_target_parallel_safe &&
is_parallel_safe(root, (Node *) activeWindows, NULL))
window_rel->consider_parallel = true;
+ /* consider_parallel_rechecking_params */
/*
* If the input rel belongs to a single FDW, so does the window rel.
@@ -4292,6 +4293,7 @@ create_distinct_paths(PlannerInfo *root,
* expressions are parallel-safe.
*/
distinct_rel->consider_parallel = input_rel->consider_parallel;
+ distinct_rel->consider_parallel_rechecking_params = input_rel->consider_parallel_rechecking_params;
/*
* If the input rel belongs to a single FDW, so does the distinct_rel.
@@ -4493,6 +4495,7 @@ create_ordered_paths(PlannerInfo *root,
*/
if (input_rel->consider_parallel && target_parallel_safe)
ordered_rel->consider_parallel = true;
+ /* consider_parallel_rechecking_params */
/*
* If the input rel belongs to a single FDW, so does the ordered_rel.
diff --git a/src/backend/optimizer/plan/subselect.c b/src/backend/optimizer/plan/subselect.c
index fd1cfe6c73..0c6fbf16a2 100644
--- a/src/backend/optimizer/plan/subselect.c
+++ b/src/backend/optimizer/plan/subselect.c
@@ -1022,6 +1022,7 @@ SS_process_ctes(PlannerInfo *root)
* parallel-safe.
*/
splan->parallel_safe = false;
+ splan->parallel_safe_ignoring_params = false;
splan->setParam = NIL;
splan->parParam = NIL;
splan->args = NIL;
@@ -2178,6 +2179,7 @@ SS_charge_for_initplans(PlannerInfo *root, RelOptInfo *final_rel)
path->startup_cost += initplan_cost;
path->total_cost += initplan_cost;
path->parallel_safe = false;
+ path->parallel_safe_ignoring_params = false;
}
/*
@@ -2186,6 +2188,7 @@ SS_charge_for_initplans(PlannerInfo *root, RelOptInfo *final_rel)
*/
final_rel->partial_pathlist = NIL;
final_rel->consider_parallel = false;
+ final_rel->consider_parallel_rechecking_params = false;
/* We needn't do set_cheapest() here, caller will do it */
}
diff --git a/src/backend/optimizer/prep/prepunion.c b/src/backend/optimizer/prep/prepunion.c
index a57bc1c2a8..c535131144 100644
--- a/src/backend/optimizer/prep/prepunion.c
+++ b/src/backend/optimizer/prep/prepunion.c
@@ -273,6 +273,7 @@ recurse_set_operations(Node *setOp, PlannerInfo *root,
*/
final_rel = fetch_upper_rel(subroot, UPPERREL_FINAL, NULL);
rel->consider_parallel = final_rel->consider_parallel;
+ rel->consider_parallel_rechecking_params = final_rel->consider_parallel_rechecking_params;
/*
* For the moment, we consider only a single Path for the subquery.
@@ -617,6 +618,7 @@ generate_union_paths(SetOperationStmt *op, PlannerInfo *root,
result_rel = fetch_upper_rel(root, UPPERREL_SETOP, relids);
result_rel->reltarget = create_pathtarget(root, tlist);
result_rel->consider_parallel = consider_parallel;
+ /* consider_parallel_rechecking_params */
/*
* Append the child results together.
--
2.20.1
[application/octet-stream] v1-0002-Parallel-query-support-for-basic-correlated-subqu.patch (75.4K, ../../CAAaqYe_x1u3V4uPiv=dJ=k2EJ7txhdq6yexJDkYZ1x1pu0QwcQ@mail.gmail.com/3-v1-0002-Parallel-query-support-for-basic-correlated-subqu.patch)
download | inline diff:
From e3df76aa8823ff05d311fd3aa4505a7f7d58b015 Mon Sep 17 00:00:00 2001
From: jcoleman <[email protected]>
Date: Fri, 27 Nov 2020 18:44:30 -0500
Subject: [PATCH v1 2/3] Parallel query support for basic correlated subqueries
Not all Params are inherently parallel-unsafe, but we can't know whether
they're parallel-safe up-front: we need contextual information for a
given path shape. Here we delay the final determination of whether or
not a Param is parallel-safe by initially verifying that it is minimally
parallel-safe for things that are inherent (e.g., no parallel-unsafe
functions or relations involved) and later re-checking that a given
usage is contextually safe (e.g., the Param is for correlation that can
happen entirely within a parallel worker (as opposed to needing to pass
values between workers).
---
doc/src/sgml/parallel.sgml | 3 +-
src/backend/nodes/copyfuncs.c | 2 +
src/backend/nodes/equalfuncs.c | 1 +
src/backend/nodes/outfuncs.c | 3 +
src/backend/nodes/readfuncs.c | 2 +
src/backend/optimizer/path/allpaths.c | 61 +++++--
src/backend/optimizer/path/equivclass.c | 4 +-
src/backend/optimizer/path/indxpath.c | 20 ++-
src/backend/optimizer/path/joinpath.c | 21 ++-
src/backend/optimizer/plan/createplan.c | 2 +
src/backend/optimizer/plan/planmain.c | 2 +-
src/backend/optimizer/plan/planner.c | 155 +++++++++++++++---
src/backend/optimizer/plan/subselect.c | 21 ++-
src/backend/optimizer/prep/prepunion.c | 1 +
src/backend/optimizer/util/clauses.c | 113 ++++++++++---
src/backend/optimizer/util/pathnode.c | 36 +++-
src/backend/optimizer/util/relnode.c | 30 +++-
src/backend/utils/misc/guc.c | 11 ++
src/include/nodes/pathnodes.h | 5 +-
src/include/nodes/plannodes.h | 1 +
src/include/nodes/primnodes.h | 1 +
src/include/optimizer/clauses.h | 4 +-
.../regress/expected/incremental_sort.out | 28 ++--
src/test/regress/expected/select_parallel.out | 137 ++++++++++++++++
src/test/regress/expected/sysviews.out | 3 +-
src/test/regress/sql/select_parallel.sql | 37 +++++
26 files changed, 604 insertions(+), 100 deletions(-)
diff --git a/doc/src/sgml/parallel.sgml b/doc/src/sgml/parallel.sgml
index 479e24a1dc..25a689f690 100644
--- a/doc/src/sgml/parallel.sgml
+++ b/doc/src/sgml/parallel.sgml
@@ -517,7 +517,8 @@ EXPLAIN SELECT * FROM pgbench_accounts WHERE filler LIKE '%x%';
<listitem>
<para>
- Plan nodes which reference a correlated <literal>SubPlan</literal>.
+ Plan nodes which reference a correlated <literal>SubPlan</literal> where
+ the result is shared between workers.
</para>
</listitem>
</itemizedlist>
diff --git a/src/backend/nodes/copyfuncs.c b/src/backend/nodes/copyfuncs.c
index 632cc31a04..240895ac83 100644
--- a/src/backend/nodes/copyfuncs.c
+++ b/src/backend/nodes/copyfuncs.c
@@ -121,6 +121,7 @@ CopyPlanFields(const Plan *from, Plan *newnode)
COPY_SCALAR_FIELD(parallel_aware);
COPY_SCALAR_FIELD(parallel_safe);
COPY_SCALAR_FIELD(async_capable);
+ COPY_SCALAR_FIELD(parallel_safe_ignoring_params);
COPY_SCALAR_FIELD(plan_node_id);
COPY_NODE_FIELD(targetlist);
COPY_NODE_FIELD(qual);
@@ -1777,6 +1778,7 @@ _copySubPlan(const SubPlan *from)
COPY_SCALAR_FIELD(useHashTable);
COPY_SCALAR_FIELD(unknownEqFalse);
COPY_SCALAR_FIELD(parallel_safe);
+ COPY_SCALAR_FIELD(parallel_safe_ignoring_params);
COPY_NODE_FIELD(setParam);
COPY_NODE_FIELD(parParam);
COPY_NODE_FIELD(args);
diff --git a/src/backend/nodes/equalfuncs.c b/src/backend/nodes/equalfuncs.c
index a410a29a17..011befabf2 100644
--- a/src/backend/nodes/equalfuncs.c
+++ b/src/backend/nodes/equalfuncs.c
@@ -459,6 +459,7 @@ _equalSubPlan(const SubPlan *a, const SubPlan *b)
COMPARE_SCALAR_FIELD(useHashTable);
COMPARE_SCALAR_FIELD(unknownEqFalse);
COMPARE_SCALAR_FIELD(parallel_safe);
+ COMPARE_SCALAR_FIELD(parallel_safe_ignoring_params);
COMPARE_NODE_FIELD(setParam);
COMPARE_NODE_FIELD(parParam);
COMPARE_NODE_FIELD(args);
diff --git a/src/backend/nodes/outfuncs.c b/src/backend/nodes/outfuncs.c
index c723f6d635..84156d6465 100644
--- a/src/backend/nodes/outfuncs.c
+++ b/src/backend/nodes/outfuncs.c
@@ -334,6 +334,7 @@ _outPlanInfo(StringInfo str, const Plan *node)
WRITE_BOOL_FIELD(parallel_aware);
WRITE_BOOL_FIELD(parallel_safe);
WRITE_BOOL_FIELD(async_capable);
+ WRITE_BOOL_FIELD(parallel_safe_ignoring_params);
WRITE_INT_FIELD(plan_node_id);
WRITE_NODE_FIELD(targetlist);
WRITE_NODE_FIELD(qual);
@@ -1372,6 +1373,7 @@ _outSubPlan(StringInfo str, const SubPlan *node)
WRITE_BOOL_FIELD(useHashTable);
WRITE_BOOL_FIELD(unknownEqFalse);
WRITE_BOOL_FIELD(parallel_safe);
+ WRITE_BOOL_FIELD(parallel_safe_ignoring_params);
WRITE_NODE_FIELD(setParam);
WRITE_NODE_FIELD(parParam);
WRITE_NODE_FIELD(args);
@@ -1770,6 +1772,7 @@ _outPathInfo(StringInfo str, const Path *node)
outBitmapset(str, NULL);
WRITE_BOOL_FIELD(parallel_aware);
WRITE_BOOL_FIELD(parallel_safe);
+ WRITE_BOOL_FIELD(parallel_safe_ignoring_params);
WRITE_INT_FIELD(parallel_workers);
WRITE_FLOAT_FIELD(rows, "%.0f");
WRITE_FLOAT_FIELD(startup_cost, "%.2f");
diff --git a/src/backend/nodes/readfuncs.c b/src/backend/nodes/readfuncs.c
index 3746668f52..2b22978616 100644
--- a/src/backend/nodes/readfuncs.c
+++ b/src/backend/nodes/readfuncs.c
@@ -1620,6 +1620,7 @@ ReadCommonPlan(Plan *local_node)
READ_BOOL_FIELD(parallel_aware);
READ_BOOL_FIELD(parallel_safe);
READ_BOOL_FIELD(async_capable);
+ READ_BOOL_FIELD(parallel_safe_ignoring_params);
READ_INT_FIELD(plan_node_id);
READ_NODE_FIELD(targetlist);
READ_NODE_FIELD(qual);
@@ -2613,6 +2614,7 @@ _readSubPlan(void)
READ_BOOL_FIELD(useHashTable);
READ_BOOL_FIELD(unknownEqFalse);
READ_BOOL_FIELD(parallel_safe);
+ READ_BOOL_FIELD(parallel_safe_ignoring_params);
READ_NODE_FIELD(setParam);
READ_NODE_FIELD(parParam);
READ_NODE_FIELD(args);
diff --git a/src/backend/optimizer/path/allpaths.c b/src/backend/optimizer/path/allpaths.c
index 45e37590d8..ae744da135 100644
--- a/src/backend/optimizer/path/allpaths.c
+++ b/src/backend/optimizer/path/allpaths.c
@@ -556,7 +556,8 @@ set_rel_pathlist(PlannerInfo *root, RelOptInfo *rel,
* (see grouping_planner).
*/
if (rel->reloptkind == RELOPT_BASEREL &&
- bms_membership(root->all_baserels) != BMS_SINGLETON)
+ bms_membership(root->all_baserels) != BMS_SINGLETON
+ && (rel->subplan_params == NIL || rte->rtekind != RTE_SUBQUERY))
generate_useful_gather_paths(root, rel, false);
/* Now find the cheapest of the paths for this rel */
@@ -592,6 +593,9 @@ static void
set_rel_consider_parallel(PlannerInfo *root, RelOptInfo *rel,
RangeTblEntry *rte)
{
+ bool parallel_safe;
+ bool parallel_safe_except_in_params;
+
/*
* The flag has previously been initialized to false, so we can just
* return if it becomes clear that we can't safely set it.
@@ -632,7 +636,7 @@ set_rel_consider_parallel(PlannerInfo *root, RelOptInfo *rel,
if (proparallel != PROPARALLEL_SAFE)
return;
- if (!is_parallel_safe(root, (Node *) rte->tablesample->args))
+ if (!is_parallel_safe(root, (Node *) rte->tablesample->args, NULL))
return;
}
@@ -700,7 +704,7 @@ set_rel_consider_parallel(PlannerInfo *root, RelOptInfo *rel,
case RTE_FUNCTION:
/* Check for parallel-restricted functions. */
- if (!is_parallel_safe(root, (Node *) rte->functions))
+ if (!is_parallel_safe(root, (Node *) rte->functions, NULL))
return;
break;
@@ -710,7 +714,7 @@ set_rel_consider_parallel(PlannerInfo *root, RelOptInfo *rel,
case RTE_VALUES:
/* Check for parallel-restricted functions. */
- if (!is_parallel_safe(root, (Node *) rte->values_lists))
+ if (!is_parallel_safe(root, (Node *) rte->values_lists, NULL))
return;
break;
@@ -747,18 +751,28 @@ set_rel_consider_parallel(PlannerInfo *root, RelOptInfo *rel,
* outer join clauses work correctly. It would likely break equivalence
* classes, too.
*/
- if (!is_parallel_safe(root, (Node *) rel->baserestrictinfo))
- return;
+ parallel_safe = is_parallel_safe(root, (Node *) rel->baserestrictinfo,
+ ¶llel_safe_except_in_params);
/*
* Likewise, if the relation's outputs are not parallel-safe, give up.
* (Usually, they're just Vars, but sometimes they're not.)
*/
- if (!is_parallel_safe(root, (Node *) rel->reltarget->exprs))
- return;
+ if (parallel_safe || parallel_safe_except_in_params)
+ {
+ bool target_parallel_safe;
+ bool target_parallel_safe_ignoring_params = false;
+
+ target_parallel_safe = is_parallel_safe(root,
+ (Node *) rel->reltarget->exprs,
+ &target_parallel_safe_ignoring_params);
+ parallel_safe = parallel_safe && target_parallel_safe;
+ parallel_safe_except_in_params = parallel_safe_except_in_params
+ && target_parallel_safe_ignoring_params;
+ }
- /* We have a winner. */
- rel->consider_parallel = true;
+ rel->consider_parallel = parallel_safe;
+ rel->consider_parallel_rechecking_params = parallel_safe_except_in_params;
}
/*
@@ -2277,9 +2291,21 @@ set_subquery_pathlist(PlannerInfo *root, RelOptInfo *rel,
pathkeys, required_outer));
}
+ /*
+ * XXX: As far as I can tell, the only time partial paths exist here
+ * is when we're going to execute multiple partial parths in parallel
+ * under a gather node (instead of executing paths serially under
+ * an append node). That means that the subquery scan path here
+ * is self-contained at this point -- so by definition it can't be
+ * reliant on lateral relids, which means we'll never have to consider
+ * rechecking params here.
+ */
+ Assert(!(rel->consider_parallel_rechecking_params && rel->partial_pathlist && !rel->consider_parallel));
+
/* If outer rel allows parallelism, do same for partial paths. */
if (rel->consider_parallel && bms_is_empty(required_outer))
{
+
/* If consider_parallel is false, there should be no partial paths. */
Assert(sub_final_rel->consider_parallel ||
sub_final_rel->partial_pathlist == NIL);
@@ -2633,7 +2659,7 @@ generate_gather_paths(PlannerInfo *root, RelOptInfo *rel, bool override_rows)
cheapest_partial_path->rows * cheapest_partial_path->parallel_workers;
simple_gather_path = (Path *)
create_gather_path(root, rel, cheapest_partial_path, rel->reltarget,
- NULL, rowsp);
+ rel->lateral_relids, rowsp);
add_path(rel, simple_gather_path);
/*
@@ -2650,7 +2676,7 @@ generate_gather_paths(PlannerInfo *root, RelOptInfo *rel, bool override_rows)
rows = subpath->rows * subpath->parallel_workers;
path = create_gather_merge_path(root, rel, subpath, rel->reltarget,
- subpath->pathkeys, NULL, rowsp);
+ subpath->pathkeys, rel->lateral_relids, rowsp);
add_path(rel, &path->path);
}
}
@@ -2752,11 +2778,15 @@ generate_useful_gather_paths(PlannerInfo *root, RelOptInfo *rel, bool override_r
double *rowsp = NULL;
List *useful_pathkeys_list = NIL;
Path *cheapest_partial_path = NULL;
+ Relids required_outer = rel->lateral_relids;
/* If there are no partial paths, there's nothing to do here. */
if (rel->partial_pathlist == NIL)
return;
+ if (!bms_is_subset(required_outer, rel->relids))
+ return;
+
/* Should we override the rel's rowcount estimate? */
if (override_rows)
rowsp = &rows;
@@ -2828,7 +2858,7 @@ generate_useful_gather_paths(PlannerInfo *root, RelOptInfo *rel, bool override_r
tmp,
rel->reltarget,
tmp->pathkeys,
- NULL,
+ required_outer,
rowsp);
add_path(rel, &path->path);
@@ -2862,7 +2892,7 @@ generate_useful_gather_paths(PlannerInfo *root, RelOptInfo *rel, bool override_r
tmp,
rel->reltarget,
tmp->pathkeys,
- NULL,
+ required_outer,
rowsp);
add_path(rel, &path->path);
@@ -3041,7 +3071,8 @@ standard_join_search(PlannerInfo *root, int levels_needed, List *initial_rels)
/*
* Except for the topmost scan/join rel, consider gathering
* partial paths. We'll do the same for the topmost scan/join rel
- * once we know the final targetlist (see grouping_planner).
+ * once we know the final targetlist (see
+ * apply_scanjoin_target_to_paths).
*/
if (lev < levels_needed)
generate_useful_gather_paths(root, rel, false);
diff --git a/src/backend/optimizer/path/equivclass.c b/src/backend/optimizer/path/equivclass.c
index 6f1abbe47d..4c176d2d49 100644
--- a/src/backend/optimizer/path/equivclass.c
+++ b/src/backend/optimizer/path/equivclass.c
@@ -897,7 +897,7 @@ find_computable_ec_member(PlannerInfo *root,
* check this last because it's a rather expensive test.
*/
if (require_parallel_safe &&
- !is_parallel_safe(root, (Node *) em->em_expr))
+ !is_parallel_safe(root, (Node *) em->em_expr, NULL))
continue;
return em; /* found usable expression */
@@ -1012,7 +1012,7 @@ relation_can_be_sorted_early(PlannerInfo *root, RelOptInfo *rel,
* check this last because it's a rather expensive test.
*/
if (require_parallel_safe &&
- !is_parallel_safe(root, (Node *) em->em_expr))
+ !is_parallel_safe(root, (Node *) em->em_expr, NULL))
continue;
return true;
diff --git a/src/backend/optimizer/path/indxpath.c b/src/backend/optimizer/path/indxpath.c
index 0e4e00eaf0..262c129ff5 100644
--- a/src/backend/optimizer/path/indxpath.c
+++ b/src/backend/optimizer/path/indxpath.c
@@ -1047,10 +1047,21 @@ build_index_paths(PlannerInfo *root, RelOptInfo *rel,
/*
* If appropriate, consider parallel index scan. We don't allow
* parallel index scan for bitmap index scans.
+ *
+ * XXX: Checking rel->consider_parallel_rechecking_params here resulted
+ * in some odd behavior on:
+ * select (select t.unique1 from tenk1 where tenk1.unique1 = t.unique1) from tenk1 t;
+ * where the total cost on the chosen plan went *up* considering
+ * the extra path.
+ *
+ * Current working theory is that this method is about base relation
+ * scans, and we only want parameterized paths to be parallelized as
+ * companions to existing parallel plans and so don't really care to
+ * consider a separate parallel index scan here.
*/
if (index->amcanparallel &&
- rel->consider_parallel && outer_relids == NULL &&
- scantype != ST_BITMAPSCAN)
+ rel->consider_parallel && outer_relids == NULL &&
+ scantype != ST_BITMAPSCAN)
{
ipath = create_index_path(root, index,
index_clauses,
@@ -1100,9 +1111,10 @@ build_index_paths(PlannerInfo *root, RelOptInfo *rel,
result = lappend(result, ipath);
/* If appropriate, consider parallel index scan */
+ /* XXX: As above here for rel->consider_parallel_rechecking_params? */
if (index->amcanparallel &&
- rel->consider_parallel && outer_relids == NULL &&
- scantype != ST_BITMAPSCAN)
+ rel->consider_parallel && outer_relids == NULL &&
+ scantype != ST_BITMAPSCAN)
{
ipath = create_index_path(root, index,
index_clauses,
diff --git a/src/backend/optimizer/path/joinpath.c b/src/backend/optimizer/path/joinpath.c
index 4c30c65564..c6af979714 100644
--- a/src/backend/optimizer/path/joinpath.c
+++ b/src/backend/optimizer/path/joinpath.c
@@ -690,6 +690,7 @@ try_partial_nestloop_path(PlannerInfo *root,
else
outerrelids = outerrel->relids;
+ /* TODO: recheck parallel safety here? */
if (!bms_is_subset(inner_paramrels, outerrelids))
return;
}
@@ -1714,16 +1715,24 @@ match_unsorted_outer(PlannerInfo *root,
* partial path and the joinrel is parallel-safe. However, we can't
* handle JOIN_UNIQUE_OUTER, because the outer path will be partial, and
* therefore we won't be able to properly guarantee uniqueness. Nor can
- * we handle joins needing lateral rels, since partial paths must not be
- * parameterized. Similarly, we can't handle JOIN_FULL and JOIN_RIGHT,
- * because they can produce false null extended rows.
+ * we handle JOIN_FULL and JOIN_RIGHT, because they can produce false null
+ * extended rows.
+ *
+ * Partial paths may only have parameters in limited cases
+ * where the parameterization is fully satisfied without sharing state
+ * between workers, so we only allow lateral rels on inputs to the join
+ * if the resulting join contains no lateral rels, the inner rel's laterals
+ * are fully satisfied by the outer rel, and the outer rel doesn't depend
+ * on the inner rel to produce any laterals.
*/
if (joinrel->consider_parallel &&
save_jointype != JOIN_UNIQUE_OUTER &&
save_jointype != JOIN_FULL &&
save_jointype != JOIN_RIGHT &&
outerrel->partial_pathlist != NIL &&
- bms_is_empty(joinrel->lateral_relids))
+ bms_is_empty(joinrel->lateral_relids) &&
+ bms_is_subset(innerrel->lateral_relids, outerrel->relids) &&
+ (bms_is_empty(outerrel->lateral_relids) || !bms_is_subset(outerrel->lateral_relids, innerrel->relids)))
{
if (nestjoinOK)
consider_parallel_nestloop(root, joinrel, outerrel, innerrel,
@@ -1838,7 +1847,9 @@ consider_parallel_nestloop(PlannerInfo *root,
Path *rcpath;
/* Can't join to an inner path that is not parallel-safe */
- if (!innerpath->parallel_safe)
+ /* TODO: recheck parallel safety of params here? */
+ if (!innerpath->parallel_safe &&
+ !(innerpath->parallel_safe_ignoring_params))
continue;
/*
diff --git a/src/backend/optimizer/plan/createplan.c b/src/backend/optimizer/plan/createplan.c
index a9aff24831..817ce04596 100644
--- a/src/backend/optimizer/plan/createplan.c
+++ b/src/backend/optimizer/plan/createplan.c
@@ -5274,6 +5274,7 @@ copy_generic_path_info(Plan *dest, Path *src)
dest->plan_width = src->pathtarget->width;
dest->parallel_aware = src->parallel_aware;
dest->parallel_safe = src->parallel_safe;
+ dest->parallel_safe_ignoring_params = src->parallel_safe_ignoring_params;
}
/*
@@ -5291,6 +5292,7 @@ copy_plan_costsize(Plan *dest, Plan *src)
dest->parallel_aware = false;
/* Assume the inserted node is parallel-safe, if child plan is. */
dest->parallel_safe = src->parallel_safe;
+ dest->parallel_safe_ignoring_params = src->parallel_safe_ignoring_params;
}
/*
diff --git a/src/backend/optimizer/plan/planmain.c b/src/backend/optimizer/plan/planmain.c
index 273ac0acf7..bdbce2b87d 100644
--- a/src/backend/optimizer/plan/planmain.c
+++ b/src/backend/optimizer/plan/planmain.c
@@ -119,7 +119,7 @@ query_planner(PlannerInfo *root,
if (root->glob->parallelModeOK &&
force_parallel_mode != FORCE_PARALLEL_OFF)
final_rel->consider_parallel =
- is_parallel_safe(root, parse->jointree->quals);
+ is_parallel_safe(root, parse->jointree->quals, NULL);
/*
* The only path for it is a trivial Result path. We cheat a
diff --git a/src/backend/optimizer/plan/planner.c b/src/backend/optimizer/plan/planner.c
index 1868c4eff4..28b8f7d8b5 100644
--- a/src/backend/optimizer/plan/planner.c
+++ b/src/backend/optimizer/plan/planner.c
@@ -150,6 +150,7 @@ static RelOptInfo *create_grouping_paths(PlannerInfo *root,
RelOptInfo *input_rel,
PathTarget *target,
bool target_parallel_safe,
+ bool target_parallel_safe_ignoring_params,
grouping_sets_data *gd);
static bool is_degenerate_grouping(PlannerInfo *root);
static void create_degenerate_grouping_paths(PlannerInfo *root,
@@ -157,6 +158,7 @@ static void create_degenerate_grouping_paths(PlannerInfo *root,
RelOptInfo *grouped_rel);
static RelOptInfo *make_grouping_rel(PlannerInfo *root, RelOptInfo *input_rel,
PathTarget *target, bool target_parallel_safe,
+ bool target_parallel_safe_ignoring_params,
Node *havingQual);
static void create_ordinary_grouping_paths(PlannerInfo *root,
RelOptInfo *input_rel,
@@ -231,6 +233,7 @@ static void apply_scanjoin_target_to_paths(PlannerInfo *root,
List *scanjoin_targets,
List *scanjoin_targets_contain_srfs,
bool scanjoin_target_parallel_safe,
+ bool scanjoin_target_parallel_safe_ignoring_params,
bool tlist_same_exprs);
static void create_partitionwise_grouping_paths(PlannerInfo *root,
RelOptInfo *input_rel,
@@ -1235,6 +1238,7 @@ grouping_planner(PlannerInfo *root, double tuple_fraction)
List *final_targets;
List *final_targets_contain_srfs;
bool final_target_parallel_safe;
+ bool final_target_parallel_safe_ignoring_params = false;
RelOptInfo *current_rel;
RelOptInfo *final_rel;
FinalPathExtraData extra;
@@ -1297,7 +1301,7 @@ grouping_planner(PlannerInfo *root, double tuple_fraction)
/* And check whether it's parallel safe */
final_target_parallel_safe =
- is_parallel_safe(root, (Node *) final_target->exprs);
+ is_parallel_safe(root, (Node *) final_target->exprs, &final_target_parallel_safe_ignoring_params);
/* The setop result tlist couldn't contain any SRFs */
Assert(!parse->hasTargetSRFs);
@@ -1331,14 +1335,17 @@ grouping_planner(PlannerInfo *root, double tuple_fraction)
List *sort_input_targets;
List *sort_input_targets_contain_srfs;
bool sort_input_target_parallel_safe;
+ bool sort_input_target_parallel_safe_ignoring_params = false;
PathTarget *grouping_target;
List *grouping_targets;
List *grouping_targets_contain_srfs;
bool grouping_target_parallel_safe;
+ bool grouping_target_parallel_safe_ignoring_params = false;
PathTarget *scanjoin_target;
List *scanjoin_targets;
List *scanjoin_targets_contain_srfs;
bool scanjoin_target_parallel_safe;
+ bool scanjoin_target_parallel_safe_ignoring_params = false;
bool scanjoin_target_same_exprs;
bool have_grouping;
WindowFuncLists *wflists = NULL;
@@ -1451,7 +1458,7 @@ grouping_planner(PlannerInfo *root, double tuple_fraction)
*/
final_target = create_pathtarget(root, root->processed_tlist);
final_target_parallel_safe =
- is_parallel_safe(root, (Node *) final_target->exprs);
+ is_parallel_safe(root, (Node *) final_target->exprs, &final_target_parallel_safe_ignoring_params);
/*
* If ORDER BY was given, consider whether we should use a post-sort
@@ -1464,12 +1471,13 @@ grouping_planner(PlannerInfo *root, double tuple_fraction)
final_target,
&have_postponed_srfs);
sort_input_target_parallel_safe =
- is_parallel_safe(root, (Node *) sort_input_target->exprs);
+ is_parallel_safe(root, (Node *) sort_input_target->exprs, &sort_input_target_parallel_safe_ignoring_params);
}
else
{
sort_input_target = final_target;
sort_input_target_parallel_safe = final_target_parallel_safe;
+ sort_input_target_parallel_safe_ignoring_params = final_target_parallel_safe_ignoring_params;
}
/*
@@ -1483,12 +1491,13 @@ grouping_planner(PlannerInfo *root, double tuple_fraction)
final_target,
activeWindows);
grouping_target_parallel_safe =
- is_parallel_safe(root, (Node *) grouping_target->exprs);
+ is_parallel_safe(root, (Node *) grouping_target->exprs, &grouping_target_parallel_safe_ignoring_params);
}
else
{
grouping_target = sort_input_target;
grouping_target_parallel_safe = sort_input_target_parallel_safe;
+ grouping_target_parallel_safe_ignoring_params = sort_input_target_parallel_safe_ignoring_params;
}
/*
@@ -1502,12 +1511,13 @@ grouping_planner(PlannerInfo *root, double tuple_fraction)
{
scanjoin_target = make_group_input_target(root, final_target);
scanjoin_target_parallel_safe =
- is_parallel_safe(root, (Node *) scanjoin_target->exprs);
+ is_parallel_safe(root, (Node *) scanjoin_target->exprs, &scanjoin_target_parallel_safe_ignoring_params);
}
else
{
scanjoin_target = grouping_target;
scanjoin_target_parallel_safe = grouping_target_parallel_safe;
+ scanjoin_target_parallel_safe_ignoring_params = grouping_target_parallel_safe_ignoring_params;
}
/*
@@ -1559,6 +1569,7 @@ grouping_planner(PlannerInfo *root, double tuple_fraction)
apply_scanjoin_target_to_paths(root, current_rel, scanjoin_targets,
scanjoin_targets_contain_srfs,
scanjoin_target_parallel_safe,
+ scanjoin_target_parallel_safe_ignoring_params,
scanjoin_target_same_exprs);
/*
@@ -1585,6 +1596,7 @@ grouping_planner(PlannerInfo *root, double tuple_fraction)
current_rel,
grouping_target,
grouping_target_parallel_safe,
+ grouping_target_parallel_safe_ignoring_params,
gset_data);
/* Fix things up if grouping_target contains SRFs */
if (parse->hasTargetSRFs)
@@ -1658,10 +1670,25 @@ grouping_planner(PlannerInfo *root, double tuple_fraction)
* not a SELECT, consider_parallel will be false for every relation in the
* query.
*/
- if (current_rel->consider_parallel &&
- is_parallel_safe(root, parse->limitOffset) &&
- is_parallel_safe(root, parse->limitCount))
- final_rel->consider_parallel = true;
+ if (current_rel->consider_parallel || current_rel->consider_parallel_rechecking_params)
+ {
+ bool limit_count_parallel_safe;
+ bool limit_offset_parallel_safe;
+ bool limit_count_parallel_safe_ignoring_params = false;
+ bool limit_offset_parallel_safe_ignoring_params = false;
+
+ limit_count_parallel_safe = is_parallel_safe(root, parse->limitCount, &limit_count_parallel_safe_ignoring_params);
+ limit_offset_parallel_safe = is_parallel_safe(root, parse->limitOffset, &limit_offset_parallel_safe_ignoring_params);
+
+ if (current_rel->consider_parallel &&
+ limit_count_parallel_safe &&
+ limit_offset_parallel_safe)
+ final_rel->consider_parallel = true;
+ if (current_rel->consider_parallel_rechecking_params &&
+ limit_count_parallel_safe_ignoring_params &&
+ limit_offset_parallel_safe_ignoring_params)
+ final_rel->consider_parallel_rechecking_params = true;
+ }
/*
* If the current_rel belongs to a single FDW, so does the final_rel.
@@ -1862,8 +1889,8 @@ grouping_planner(PlannerInfo *root, double tuple_fraction)
* Generate partial paths for final_rel, too, if outer query levels might
* be able to make use of them.
*/
- if (final_rel->consider_parallel && root->query_level > 1 &&
- !limit_needed(parse))
+ if ((final_rel->consider_parallel || final_rel->consider_parallel_rechecking_params) &&
+ root->query_level > 1 && !limit_needed(parse))
{
Assert(!parse->rowMarks && parse->commandType == CMD_SELECT);
foreach(lc, current_rel->partial_pathlist)
@@ -3275,6 +3302,7 @@ create_grouping_paths(PlannerInfo *root,
RelOptInfo *input_rel,
PathTarget *target,
bool target_parallel_safe,
+ bool target_parallel_safe_ignoring_params,
grouping_sets_data *gd)
{
Query *parse = root->parse;
@@ -3290,7 +3318,9 @@ create_grouping_paths(PlannerInfo *root,
* aggregation paths.
*/
grouped_rel = make_grouping_rel(root, input_rel, target,
- target_parallel_safe, parse->havingQual);
+ target_parallel_safe,
+ target_parallel_safe_ignoring_params,
+ parse->havingQual);
/*
* Create either paths for a degenerate grouping or paths for ordinary
@@ -3351,6 +3381,7 @@ create_grouping_paths(PlannerInfo *root,
extra.flags = flags;
extra.target_parallel_safe = target_parallel_safe;
+ extra.target_parallel_safe_ignoring_params = target_parallel_safe_ignoring_params;
extra.havingQual = parse->havingQual;
extra.targetList = parse->targetList;
extra.partial_costs_set = false;
@@ -3386,7 +3417,7 @@ create_grouping_paths(PlannerInfo *root,
static RelOptInfo *
make_grouping_rel(PlannerInfo *root, RelOptInfo *input_rel,
PathTarget *target, bool target_parallel_safe,
- Node *havingQual)
+ bool target_parallel_safe_ignoring_params, Node *havingQual)
{
RelOptInfo *grouped_rel;
@@ -3414,9 +3445,21 @@ make_grouping_rel(PlannerInfo *root, RelOptInfo *input_rel,
* can't be parallel-safe, either. Otherwise, it's parallel-safe if the
* target list and HAVING quals are parallel-safe.
*/
- if (input_rel->consider_parallel && target_parallel_safe &&
- is_parallel_safe(root, (Node *) havingQual))
- grouped_rel->consider_parallel = true;
+ if ((input_rel->consider_parallel || input_rel->consider_parallel_rechecking_params)
+ && (target_parallel_safe || target_parallel_safe_ignoring_params))
+ {
+ bool having_qual_parallel_safe;
+ bool having_qual_parallel_safe_ignoring_params = false;
+
+ having_qual_parallel_safe = is_parallel_safe(root, (Node *) havingQual,
+ &having_qual_parallel_safe_ignoring_params);
+
+ grouped_rel->consider_parallel = input_rel->consider_parallel &&
+ having_qual_parallel_safe && target_parallel_safe;
+ grouped_rel->consider_parallel_rechecking_params =
+ input_rel->consider_parallel_rechecking_params &&
+ having_qual_parallel_safe_ignoring_params && target_parallel_safe_ignoring_params;
+ }
/*
* If the input rel belongs to a single FDW, so does the grouped rel.
@@ -4043,7 +4086,7 @@ create_window_paths(PlannerInfo *root,
* target list and active windows for non-parallel-safe constructs.
*/
if (input_rel->consider_parallel && output_target_parallel_safe &&
- is_parallel_safe(root, (Node *) activeWindows))
+ is_parallel_safe(root, (Node *) activeWindows, NULL))
window_rel->consider_parallel = true;
/*
@@ -5602,6 +5645,7 @@ adjust_paths_for_srfs(PlannerInfo *root, RelOptInfo *rel,
PathTarget *thistarget = lfirst_node(PathTarget, lc1);
bool contains_srfs = (bool) lfirst_int(lc2);
+ /* TODO: How do we know the new target is parallel safe? */
/* If this level doesn't contain SRFs, do regular projection */
if (contains_srfs)
newpath = (Path *) create_set_projection_path(root,
@@ -5918,8 +5962,8 @@ plan_create_index_workers(Oid tableOid, Oid indexOid)
* safe.
*/
if (heap->rd_rel->relpersistence == RELPERSISTENCE_TEMP ||
- !is_parallel_safe(root, (Node *) RelationGetIndexExpressions(index)) ||
- !is_parallel_safe(root, (Node *) RelationGetIndexPredicate(index)))
+ !is_parallel_safe(root, (Node *) RelationGetIndexExpressions(index), NULL) ||
+ !is_parallel_safe(root, (Node *) RelationGetIndexPredicate(index), NULL))
{
parallel_workers = 0;
goto done;
@@ -6382,6 +6426,8 @@ create_partial_grouping_paths(PlannerInfo *root,
grouped_rel->relids);
partially_grouped_rel->consider_parallel =
grouped_rel->consider_parallel;
+ partially_grouped_rel->consider_parallel_rechecking_params =
+ grouped_rel->consider_parallel_rechecking_params;
partially_grouped_rel->reloptkind = grouped_rel->reloptkind;
partially_grouped_rel->serverid = grouped_rel->serverid;
partially_grouped_rel->userid = grouped_rel->userid;
@@ -6845,6 +6891,7 @@ apply_scanjoin_target_to_paths(PlannerInfo *root,
List *scanjoin_targets,
List *scanjoin_targets_contain_srfs,
bool scanjoin_target_parallel_safe,
+ bool scanjoin_target_parallel_safe_ignoring_params,
bool tlist_same_exprs)
{
bool rel_is_partitioned = IS_PARTITIONED_REL(rel);
@@ -6854,6 +6901,11 @@ apply_scanjoin_target_to_paths(PlannerInfo *root,
/* This recurses, so be paranoid. */
check_stack_depth();
+ /*
+ * TOOD: when/how do we want to generate gather paths if
+ * scanjoin_target_parallel_safe_ignoring_params = true
+ */
+
/*
* If the rel is partitioned, we want to drop its existing paths and
* generate new ones. This function would still be correct if we kept the
@@ -6894,6 +6946,64 @@ apply_scanjoin_target_to_paths(PlannerInfo *root,
generate_useful_gather_paths(root, rel, false);
/* Can't use parallel query above this level. */
+
+ /*
+ * There are cases where:
+ * (rel->consider_parallel &&
+ * !scanjoin_target_parallel_safe &&
+ * scanjoin_target_parallel_safe_ignoring_params)
+ * is true at this point. See longer commment below.
+ */
+ if (!(rel->consider_parallel_rechecking_params && scanjoin_target_parallel_safe_ignoring_params))
+ {
+ /*
+ * TODO: if we limit this to this condition, we're pushing off the
+ * checks as to whether or not a given param usage is safe in the
+ * context of a given path (in the context of a given rel?). That
+ * almost certainly means we'd have to add other checks later (maybe
+ * just on lateral/relids and not parallel safety overall), because
+ * at the end of grouping_planner() we copy partial paths to the
+ * final_rel, and while that path may be acceptable in some contexts
+ * it may not be in all contexts.
+ *
+ * OTOH if we're only dependent on PARAM_EXEC params, and we already
+ * know that subpath->param_info == NULL holds (and that seems like
+ * it must since we were going to replace the path target anyway...
+ * though the one caveat is from the original form of this function
+ * we'd only ever actually assert that for paths not partial paths)
+ * then if a param shows up in the target why would it not be parallel
+ * safe.
+ *
+ * Adding to the mystery even with the original form of this function
+ * we still end up with parallel paths where I'd expect this to
+ * disallow them. For example:
+ *
+ * SELECT '' AS six, f1 AS "Correlated Field", f3 AS "Second Field"
+ * FROM SUBSELECT_TBL upper
+ * WHERE f3 IN (
+ * SELECT upper.f1 + f2
+ * FROM SUBSELECT_TBL
+ * WHERE f2 = CAST(f3 AS integer)
+ * );
+ *
+ * ends up with the correlated query underneath parallel plan despite
+ * its target containing a param, and therefore this function marking
+ * the rel as consider_parallel=false and removing the partial paths.
+ *
+ * But the plan as a whole is parallel safe, and so the subplan is also
+ * parallel safe, which means we can incorporate it into a full parallel
+ * plan. In other words, this is a parallel safe, but not parallel aware
+ * subplan (and regular, not parallel, seq scan inside that subplan).
+ * It's not a partial path; it'a a full path that is executed as a subquery.
+ *
+ * Current conclusion: it's fine for subplans, which is the case we're
+ * currently targeting anyway. And it might even be the only case that
+ * matters at all.
+ */
+ /* rel->consider_parallel_rechecking_params = false; */
+ /* rel->partial_pathlist = NIL; */
+ }
+ rel->consider_parallel_rechecking_params = false;
rel->partial_pathlist = NIL;
rel->consider_parallel = false;
}
@@ -7026,6 +7136,7 @@ apply_scanjoin_target_to_paths(PlannerInfo *root,
child_scanjoin_targets,
scanjoin_targets_contain_srfs,
scanjoin_target_parallel_safe,
+ scanjoin_target_parallel_safe_ignoring_params,
tlist_same_exprs);
/* Save non-dummy children for Append paths. */
@@ -7043,6 +7154,11 @@ apply_scanjoin_target_to_paths(PlannerInfo *root,
* avoid creating multiple Gather nodes within the same plan. We must do
* this after all paths have been generated and before set_cheapest, since
* one of the generated paths may turn out to be the cheapest one.
+ *
+ * TODO: This is the same problem as earlier in this function: when allowing
+ * "parallel safe ignoring params" paths here we don't actually know we are
+ * safe in any possible context just possibly safe in the context of the
+ * right rel.
*/
if (rel->consider_parallel && !IS_OTHER_REL(rel))
generate_useful_gather_paths(root, rel, false);
@@ -7146,6 +7262,7 @@ create_partitionwise_grouping_paths(PlannerInfo *root,
child_grouped_rel = make_grouping_rel(root, child_input_rel,
child_target,
extra->target_parallel_safe,
+ extra->target_parallel_safe_ignoring_params,
child_extra.havingQual);
/* Create grouping paths for this child relation. */
diff --git a/src/backend/optimizer/plan/subselect.c b/src/backend/optimizer/plan/subselect.c
index 0881a208ac..fd1cfe6c73 100644
--- a/src/backend/optimizer/plan/subselect.c
+++ b/src/backend/optimizer/plan/subselect.c
@@ -342,6 +342,7 @@ build_subplan(PlannerInfo *root, Plan *plan, PlannerInfo *subroot,
splan->useHashTable = false;
splan->unknownEqFalse = unknownEqFalse;
splan->parallel_safe = plan->parallel_safe;
+ splan->parallel_safe_ignoring_params = plan->parallel_safe_ignoring_params;
splan->setParam = NIL;
splan->parParam = NIL;
splan->args = NIL;
@@ -1939,6 +1940,7 @@ process_sublinks_mutator(Node *node, process_sublinks_context *context)
{
SubLink *sublink = (SubLink *) node;
Node *testexpr;
+ Node *result;
/*
* First, recursively process the lefthand-side expressions, if any.
@@ -1950,12 +1952,29 @@ process_sublinks_mutator(Node *node, process_sublinks_context *context)
/*
* Now build the SubPlan node and make the expr to return.
*/
- return make_subplan(context->root,
+ result = make_subplan(context->root,
(Query *) sublink->subselect,
sublink->subLinkType,
sublink->subLinkId,
testexpr,
context->isTopQual);
+
+ /*
+ * If planning determined that a subpath was parallel safe as long
+ * as required params are provided by each individual worker then we
+ * can mark the resulting subplan actually parallel safe since we now
+ * know for certain how that path will be used.
+ */
+ if (IsA(result, SubPlan) && !((SubPlan*)result)->parallel_safe
+ && ((SubPlan*)result)->parallel_safe_ignoring_params
+ && enable_parallel_params_recheck)
+ {
+ Plan *subplan = planner_subplan_get_plan(context->root, (SubPlan*)result);
+ ((SubPlan*)result)->parallel_safe = is_parallel_safe(context->root, testexpr, NULL);
+ subplan->parallel_safe = ((SubPlan*)result)->parallel_safe;
+ }
+
+ return result;
}
/*
diff --git a/src/backend/optimizer/prep/prepunion.c b/src/backend/optimizer/prep/prepunion.c
index 037dfaacfd..a57bc1c2a8 100644
--- a/src/backend/optimizer/prep/prepunion.c
+++ b/src/backend/optimizer/prep/prepunion.c
@@ -409,6 +409,7 @@ recurse_set_operations(Node *setOp, PlannerInfo *root,
Assert(subpath->param_info == NULL);
/* avoid apply_projection_to_path, in case of multiple refs */
+ /* TODO: how to we know the target is parallel safe? */
path = (Path *) create_projection_path(root, subpath->parent,
subpath, target);
lfirst(lc) = path;
diff --git a/src/backend/optimizer/util/clauses.c b/src/backend/optimizer/util/clauses.c
index d9ad4efc5e..4c188b85a4 100644
--- a/src/backend/optimizer/util/clauses.c
+++ b/src/backend/optimizer/util/clauses.c
@@ -54,6 +54,15 @@
#include "utils/syscache.h"
#include "utils/typcache.h"
+bool enable_parallel_params_recheck = true;
+
+typedef struct
+{
+ PlannerInfo *root;
+ AggSplit aggsplit;
+ AggClauseCosts *costs;
+} get_agg_clause_costs_context;
+
typedef struct
{
ParamListInfo boundParams;
@@ -87,6 +96,8 @@ typedef struct
{
char max_hazard; /* worst proparallel hazard found so far */
char max_interesting; /* worst proparallel hazard of interest */
+ char max_hazard_ignoring_params;
+ bool check_params_independently;
List *safe_param_ids; /* PARAM_EXEC Param IDs to treat as safe */
} max_parallel_hazard_context;
@@ -620,19 +631,27 @@ max_parallel_hazard(Query *parse)
context.max_hazard = PROPARALLEL_SAFE;
context.max_interesting = PROPARALLEL_UNSAFE;
context.safe_param_ids = NIL;
+ context.check_params_independently = false;
(void) max_parallel_hazard_walker((Node *) parse, &context);
return context.max_hazard;
}
/*
* is_parallel_safe
- * Detect whether the given expr contains only parallel-safe functions
+ * Detect whether the given expr contains only parallel safe funcions
+ * XXX: It does more than functions?
+ *
+ * If provided, safe_ignoring_params will be set the result of running the same
+ * parallel safety checks with the exception that params will be allowed. This
+ * value is useful since params are not inherently parallel unsafe, but rather
+ * their usage context (whether or not the worker is able to provide the value)
+ * determines parallel safety.
*
* root->glob->maxParallelHazard must previously have been set to the
- * result of max_parallel_hazard() on the whole query.
+ * result of max_parallel_hazard() on the whole query
*/
bool
-is_parallel_safe(PlannerInfo *root, Node *node)
+is_parallel_safe(PlannerInfo *root, Node *node, bool *safe_ignoring_params)
{
max_parallel_hazard_context context;
PlannerInfo *proot;
@@ -649,8 +668,10 @@ is_parallel_safe(PlannerInfo *root, Node *node)
return true;
/* Else use max_parallel_hazard's search logic, but stop on RESTRICTED */
context.max_hazard = PROPARALLEL_SAFE;
+ context.max_hazard_ignoring_params = PROPARALLEL_SAFE;
context.max_interesting = PROPARALLEL_RESTRICTED;
context.safe_param_ids = NIL;
+ context.check_params_independently = safe_ignoring_params != NULL;
/*
* The params that refer to the same or parent query level are considered
@@ -668,12 +689,17 @@ is_parallel_safe(PlannerInfo *root, Node *node)
}
}
- return !max_parallel_hazard_walker(node, &context);
+ (void) max_parallel_hazard_walker(node, &context);
+
+ if (safe_ignoring_params)
+ *safe_ignoring_params = context.max_hazard_ignoring_params == PROPARALLEL_SAFE;
+
+ return context.max_hazard == PROPARALLEL_SAFE;
}
/* core logic for all parallel-hazard checks */
static bool
-max_parallel_hazard_test(char proparallel, max_parallel_hazard_context *context)
+max_parallel_hazard_test(char proparallel, max_parallel_hazard_context *context, bool from_param)
{
switch (proparallel)
{
@@ -684,12 +710,16 @@ max_parallel_hazard_test(char proparallel, max_parallel_hazard_context *context)
/* increase max_hazard to RESTRICTED */
Assert(context->max_hazard != PROPARALLEL_UNSAFE);
context->max_hazard = proparallel;
+ if (!from_param)
+ context->max_hazard_ignoring_params = proparallel;
/* done if we are not expecting any unsafe functions */
if (context->max_interesting == proparallel)
return true;
break;
case PROPARALLEL_UNSAFE:
context->max_hazard = proparallel;
+ if (!from_param)
+ context->max_hazard_ignoring_params = proparallel;
/* we're always done at the first unsafe construct */
return true;
default:
@@ -704,7 +734,41 @@ static bool
max_parallel_hazard_checker(Oid func_id, void *context)
{
return max_parallel_hazard_test(func_parallel(func_id),
- (max_parallel_hazard_context *) context);
+ (max_parallel_hazard_context *) context, false);
+}
+
+static bool
+max_parallel_hazard_walker_can_short_circuit(max_parallel_hazard_context *context)
+{
+ if (!context->check_params_independently)
+ return true;
+
+ switch (context->max_hazard)
+ {
+ case PROPARALLEL_SAFE:
+ /* nothing to see here, move along */
+ break;
+ case PROPARALLEL_RESTRICTED:
+ if (context->max_interesting == PROPARALLEL_RESTRICTED)
+ return context->max_hazard_ignoring_params != PROPARALLEL_SAFE;
+
+ /*
+ * We haven't even met our max interesting yet, so
+ * we certainly can't short-circuit.
+ */
+ break;
+ case PROPARALLEL_UNSAFE:
+ if (context->max_interesting == PROPARALLEL_RESTRICTED)
+ return context->max_hazard_ignoring_params != PROPARALLEL_SAFE;
+ else if (context->max_interesting == PROPARALLEL_UNSAFE)
+ return context->max_hazard_ignoring_params == PROPARALLEL_UNSAFE;
+
+ break;
+ default:
+ elog(ERROR, "unrecognized proparallel value \"%c\"", context->max_hazard);
+ break;
+ }
+ return false;
}
static bool
@@ -716,7 +780,7 @@ max_parallel_hazard_walker(Node *node, max_parallel_hazard_context *context)
/* Check for hazardous functions in node itself */
if (check_functions_in_node(node, max_parallel_hazard_checker,
context))
- return true;
+ return max_parallel_hazard_walker_can_short_circuit(context);
/*
* It should be OK to treat MinMaxExpr as parallel-safe, since btree
@@ -731,14 +795,14 @@ max_parallel_hazard_walker(Node *node, max_parallel_hazard_context *context)
*/
if (IsA(node, CoerceToDomain))
{
- if (max_parallel_hazard_test(PROPARALLEL_RESTRICTED, context))
- return true;
+ if (max_parallel_hazard_test(PROPARALLEL_RESTRICTED, context, false))
+ return max_parallel_hazard_walker_can_short_circuit(context);
}
else if (IsA(node, NextValueExpr))
{
- if (max_parallel_hazard_test(PROPARALLEL_UNSAFE, context))
- return true;
+ if (max_parallel_hazard_test(PROPARALLEL_UNSAFE, context, false))
+ return max_parallel_hazard_walker_can_short_circuit(context);
}
/*
@@ -751,8 +815,8 @@ max_parallel_hazard_walker(Node *node, max_parallel_hazard_context *context)
*/
else if (IsA(node, WindowFunc))
{
- if (max_parallel_hazard_test(PROPARALLEL_RESTRICTED, context))
- return true;
+ if (max_parallel_hazard_test(PROPARALLEL_RESTRICTED, context, false))
+ return max_parallel_hazard_walker_can_short_circuit(context);
}
/*
@@ -771,8 +835,8 @@ max_parallel_hazard_walker(Node *node, max_parallel_hazard_context *context)
*/
else if (IsA(node, SubLink))
{
- if (max_parallel_hazard_test(PROPARALLEL_RESTRICTED, context))
- return true;
+ if (max_parallel_hazard_test(PROPARALLEL_RESTRICTED, context, false))
+ return max_parallel_hazard_walker_can_short_circuit(context);
}
/*
@@ -787,18 +851,23 @@ max_parallel_hazard_walker(Node *node, max_parallel_hazard_context *context)
List *save_safe_param_ids;
if (!subplan->parallel_safe &&
- max_parallel_hazard_test(PROPARALLEL_RESTRICTED, context))
+ (!enable_parallel_params_recheck || !subplan->parallel_safe_ignoring_params) &&
+ max_parallel_hazard_test(PROPARALLEL_RESTRICTED, context, false) &&
+ max_parallel_hazard_walker_can_short_circuit(context))
return true;
save_safe_param_ids = context->safe_param_ids;
context->safe_param_ids = list_concat_copy(context->safe_param_ids,
subplan->paramIds);
- if (max_parallel_hazard_walker(subplan->testexpr, context))
- return true; /* no need to restore safe_param_ids */
+ if (max_parallel_hazard_walker(subplan->testexpr, context) &&
+ max_parallel_hazard_walker_can_short_circuit(context))
+ /* no need to restore safe_param_ids */
+ return true;
+
list_free(context->safe_param_ids);
context->safe_param_ids = save_safe_param_ids;
/* we must also check args, but no special Param treatment there */
if (max_parallel_hazard_walker((Node *) subplan->args, context))
- return true;
+ return max_parallel_hazard_walker_can_short_circuit(context);
/* don't want to recurse normally, so we're done */
return false;
}
@@ -820,8 +889,8 @@ max_parallel_hazard_walker(Node *node, max_parallel_hazard_context *context)
if (param->paramkind != PARAM_EXEC ||
!list_member_int(context->safe_param_ids, param->paramid))
{
- if (max_parallel_hazard_test(PROPARALLEL_RESTRICTED, context))
- return true;
+ if (max_parallel_hazard_test(PROPARALLEL_RESTRICTED, context, true))
+ return max_parallel_hazard_walker_can_short_circuit(context);
}
return false; /* nothing to recurse to */
}
@@ -839,7 +908,7 @@ max_parallel_hazard_walker(Node *node, max_parallel_hazard_context *context)
if (query->rowMarks != NULL)
{
context->max_hazard = PROPARALLEL_UNSAFE;
- return true;
+ return max_parallel_hazard_walker_can_short_circuit(context);
}
/* Recurse into subselects */
diff --git a/src/backend/optimizer/util/pathnode.c b/src/backend/optimizer/util/pathnode.c
index b248b038e0..93956f3828 100644
--- a/src/backend/optimizer/util/pathnode.c
+++ b/src/backend/optimizer/util/pathnode.c
@@ -756,10 +756,10 @@ add_partial_path(RelOptInfo *parent_rel, Path *new_path)
CHECK_FOR_INTERRUPTS();
/* Path to be added must be parallel safe. */
- Assert(new_path->parallel_safe);
+ Assert(new_path->parallel_safe || new_path->parallel_safe_ignoring_params);
/* Relation should be OK for parallelism, too. */
- Assert(parent_rel->consider_parallel);
+ Assert(parent_rel->consider_parallel || parent_rel->consider_parallel_rechecking_params);
/*
* As in add_path, throw out any paths which are dominated by the new
@@ -938,6 +938,7 @@ create_seqscan_path(PlannerInfo *root, RelOptInfo *rel,
required_outer);
pathnode->parallel_aware = parallel_workers > 0 ? true : false;
pathnode->parallel_safe = rel->consider_parallel;
+ pathnode->parallel_safe_ignoring_params = rel->consider_parallel_rechecking_params;
pathnode->parallel_workers = parallel_workers;
pathnode->pathkeys = NIL; /* seqscan has unordered result */
@@ -1016,6 +1017,7 @@ create_index_path(PlannerInfo *root,
required_outer);
pathnode->path.parallel_aware = false;
pathnode->path.parallel_safe = rel->consider_parallel;
+ pathnode->path.parallel_safe_ignoring_params = rel->consider_parallel_rechecking_params;
pathnode->path.parallel_workers = 0;
pathnode->path.pathkeys = pathkeys;
@@ -1868,7 +1870,7 @@ create_gather_merge_path(PlannerInfo *root, RelOptInfo *rel, Path *subpath,
Cost input_startup_cost = 0;
Cost input_total_cost = 0;
- Assert(subpath->parallel_safe);
+ Assert(subpath->parallel_safe || subpath->parallel_safe_ignoring_params);
Assert(pathkeys);
pathnode->path.pathtype = T_GatherMerge;
@@ -1956,7 +1958,7 @@ create_gather_path(PlannerInfo *root, RelOptInfo *rel, Path *subpath,
{
GatherPath *pathnode = makeNode(GatherPath);
- Assert(subpath->parallel_safe);
+ Assert(subpath->parallel_safe || subpath->parallel_safe_ignoring_params);
pathnode->path.pathtype = T_Gather;
pathnode->path.parent = rel;
@@ -2003,6 +2005,8 @@ create_subqueryscan_path(PlannerInfo *root, RelOptInfo *rel, Path *subpath,
pathnode->path.parallel_aware = false;
pathnode->path.parallel_safe = rel->consider_parallel &&
subpath->parallel_safe;
+ pathnode->path.parallel_safe_ignoring_params = rel->consider_parallel_rechecking_params &&
+ subpath->parallel_safe_ignoring_params;
pathnode->path.parallel_workers = subpath->parallel_workers;
pathnode->path.pathkeys = pathkeys;
pathnode->subpath = subpath;
@@ -2420,6 +2424,8 @@ create_nestloop_path(PlannerInfo *root,
NestPath *pathnode = makeNode(NestPath);
Relids inner_req_outer = PATH_REQ_OUTER(inner_path);
+ /* TODO: Assert lateral relids subset safety? */
+
/*
* If the inner path is parameterized by the outer, we must drop any
* restrict_clauses that are due to be moved into the inner path. We have
@@ -2460,6 +2466,8 @@ create_nestloop_path(PlannerInfo *root,
pathnode->path.parallel_aware = false;
pathnode->path.parallel_safe = joinrel->consider_parallel &&
outer_path->parallel_safe && inner_path->parallel_safe;
+ pathnode->path.parallel_safe_ignoring_params = joinrel->consider_parallel_rechecking_params &&
+ outer_path->parallel_safe_ignoring_params && inner_path->parallel_safe_ignoring_params;
/* This is a foolish way to estimate parallel_workers, but for now... */
pathnode->path.parallel_workers = outer_path->parallel_workers;
pathnode->path.pathkeys = pathkeys;
@@ -2633,6 +2641,8 @@ create_projection_path(PlannerInfo *root,
{
ProjectionPath *pathnode = makeNode(ProjectionPath);
PathTarget *oldtarget = subpath->pathtarget;
+ bool target_parallel_safe;
+ bool target_parallel_safe_ignoring_params = false;
pathnode->path.pathtype = T_Result;
pathnode->path.parent = rel;
@@ -2640,9 +2650,12 @@ create_projection_path(PlannerInfo *root,
/* For now, assume we are above any joins, so no parameterization */
pathnode->path.param_info = NULL;
pathnode->path.parallel_aware = false;
+ target_parallel_safe = is_parallel_safe(root, (Node *) target->exprs,
+ &target_parallel_safe_ignoring_params);
pathnode->path.parallel_safe = rel->consider_parallel &&
- subpath->parallel_safe &&
- is_parallel_safe(root, (Node *) target->exprs);
+ subpath->parallel_safe && target_parallel_safe;
+ pathnode->path.parallel_safe_ignoring_params = rel->consider_parallel_rechecking_params &&
+ subpath->parallel_safe_ignoring_params && target_parallel_safe_ignoring_params;
pathnode->path.parallel_workers = subpath->parallel_workers;
/* Projection does not change the sort order */
pathnode->path.pathkeys = subpath->pathkeys;
@@ -2749,7 +2762,7 @@ apply_projection_to_path(PlannerInfo *root,
* parallel-safe in the target expressions, then we can't.
*/
if ((IsA(path, GatherPath) || IsA(path, GatherMergePath)) &&
- is_parallel_safe(root, (Node *) target->exprs))
+ is_parallel_safe(root, (Node *) target->exprs, NULL))
{
/*
* We always use create_projection_path here, even if the subpath is
@@ -2783,7 +2796,7 @@ apply_projection_to_path(PlannerInfo *root,
}
}
else if (path->parallel_safe &&
- !is_parallel_safe(root, (Node *) target->exprs))
+ !is_parallel_safe(root, (Node *) target->exprs, NULL))
{
/*
* We're inserting a parallel-restricted target list into a path
@@ -2791,6 +2804,7 @@ apply_projection_to_path(PlannerInfo *root,
* safe.
*/
path->parallel_safe = false;
+ path->parallel_safe_ignoring_params = false; /* TODO */
}
return path;
@@ -2823,7 +2837,7 @@ create_set_projection_path(PlannerInfo *root,
pathnode->path.parallel_aware = false;
pathnode->path.parallel_safe = rel->consider_parallel &&
subpath->parallel_safe &&
- is_parallel_safe(root, (Node *) target->exprs);
+ is_parallel_safe(root, (Node *) target->exprs, NULL);
pathnode->path.parallel_workers = subpath->parallel_workers;
/* Projection does not change the sort order XXX? */
pathnode->path.pathkeys = subpath->pathkeys;
@@ -3100,6 +3114,8 @@ create_agg_path(PlannerInfo *root,
pathnode->path.parallel_aware = false;
pathnode->path.parallel_safe = rel->consider_parallel &&
subpath->parallel_safe;
+ pathnode->path.parallel_safe_ignoring_params = rel->consider_parallel_rechecking_params &&
+ subpath->parallel_safe_ignoring_params;
pathnode->path.parallel_workers = subpath->parallel_workers;
if (aggstrategy == AGG_SORTED)
pathnode->path.pathkeys = subpath->pathkeys; /* preserves order */
@@ -3721,6 +3737,8 @@ create_limit_path(PlannerInfo *root, RelOptInfo *rel,
pathnode->path.parallel_aware = false;
pathnode->path.parallel_safe = rel->consider_parallel &&
subpath->parallel_safe;
+ pathnode->path.parallel_safe_ignoring_params = rel->consider_parallel_rechecking_params &&
+ subpath->parallel_safe_ignoring_params;
pathnode->path.parallel_workers = subpath->parallel_workers;
pathnode->path.rows = subpath->rows;
pathnode->path.startup_cost = subpath->startup_cost;
diff --git a/src/backend/optimizer/util/relnode.c b/src/backend/optimizer/util/relnode.c
index e105a4d5f1..d026db8759 100644
--- a/src/backend/optimizer/util/relnode.c
+++ b/src/backend/optimizer/util/relnode.c
@@ -213,6 +213,7 @@ build_simple_rel(PlannerInfo *root, int relid, RelOptInfo *parent)
rel->consider_startup = (root->tuple_fraction > 0);
rel->consider_param_startup = false; /* might get changed later */
rel->consider_parallel = false; /* might get changed later */
+ rel->consider_parallel_rechecking_params = false; /* might get changed later */
rel->reltarget = create_empty_pathtarget();
rel->pathlist = NIL;
rel->ppilist = NIL;
@@ -616,6 +617,7 @@ build_join_rel(PlannerInfo *root,
joinrel->consider_startup = (root->tuple_fraction > 0);
joinrel->consider_param_startup = false;
joinrel->consider_parallel = false;
+ joinrel->consider_parallel_rechecking_params = false;
joinrel->reltarget = create_empty_pathtarget();
joinrel->pathlist = NIL;
joinrel->ppilist = NIL;
@@ -741,10 +743,27 @@ build_join_rel(PlannerInfo *root,
* take; therefore, we should make the same decision here however we get
* here.
*/
- if (inner_rel->consider_parallel && outer_rel->consider_parallel &&
- is_parallel_safe(root, (Node *) restrictlist) &&
- is_parallel_safe(root, (Node *) joinrel->reltarget->exprs))
- joinrel->consider_parallel = true;
+ if ((inner_rel->consider_parallel || inner_rel->consider_parallel_rechecking_params)
+ && (outer_rel->consider_parallel || outer_rel->consider_parallel_rechecking_params))
+ {
+ bool restrictlist_parallel_safe;
+ bool restrictlist_parallel_safe_ignoring_params = false;
+ bool target_parallel_safe;
+ bool target_parallel_safe_ignoring_params = false;
+
+ restrictlist_parallel_safe = is_parallel_safe(root, (Node *) restrictlist, &restrictlist_parallel_safe_ignoring_params);
+ target_parallel_safe = is_parallel_safe(root, (Node *) joinrel->reltarget->exprs, &target_parallel_safe_ignoring_params);
+
+ if (inner_rel->consider_parallel && outer_rel->consider_parallel
+ && restrictlist_parallel_safe && target_parallel_safe)
+ joinrel->consider_parallel = true;
+
+ if (inner_rel->consider_parallel_rechecking_params
+ && outer_rel->consider_parallel_rechecking_params
+ && restrictlist_parallel_safe_ignoring_params
+ && target_parallel_safe_ignoring_params)
+ joinrel->consider_parallel_rechecking_params = true;
+ }
/* Add the joinrel to the PlannerInfo. */
add_join_rel(root, joinrel);
@@ -803,6 +822,7 @@ build_child_join_rel(PlannerInfo *root, RelOptInfo *outer_rel,
joinrel->consider_startup = (root->tuple_fraction > 0);
joinrel->consider_param_startup = false;
joinrel->consider_parallel = false;
+ joinrel->consider_parallel_rechecking_params = false;
joinrel->reltarget = create_empty_pathtarget();
joinrel->pathlist = NIL;
joinrel->ppilist = NIL;
@@ -889,6 +909,7 @@ build_child_join_rel(PlannerInfo *root, RelOptInfo *outer_rel,
/* Child joinrel is parallel safe if parent is parallel safe. */
joinrel->consider_parallel = parent_joinrel->consider_parallel;
+ joinrel->consider_parallel_rechecking_params = parent_joinrel->consider_parallel_rechecking_params;
/* Set estimates of the child-joinrel's size. */
set_joinrel_size_estimates(root, joinrel, outer_rel, inner_rel,
@@ -1233,6 +1254,7 @@ fetch_upper_rel(PlannerInfo *root, UpperRelationKind kind, Relids relids)
upperrel->consider_startup = (root->tuple_fraction > 0);
upperrel->consider_param_startup = false;
upperrel->consider_parallel = false; /* might get changed later */
+ upperrel->consider_parallel_rechecking_params = false; /* might get changed later */
upperrel->reltarget = create_empty_pathtarget();
upperrel->pathlist = NIL;
upperrel->cheapest_startup_path = NULL;
diff --git a/src/backend/utils/misc/guc.c b/src/backend/utils/misc/guc.c
index b130874bdc..1fbab55e2c 100644
--- a/src/backend/utils/misc/guc.c
+++ b/src/backend/utils/misc/guc.c
@@ -58,6 +58,7 @@
#include "libpq/libpq.h"
#include "libpq/pqformat.h"
#include "miscadmin.h"
+#include "optimizer/clauses.h"
#include "optimizer/cost.h"
#include "optimizer/geqo.h"
#include "optimizer/optimizer.h"
@@ -955,6 +956,16 @@ static const unit_conversion time_unit_conversion_table[] =
static struct config_bool ConfigureNamesBool[] =
{
+ {
+ {"enable_parallel_params_recheck", PGC_USERSET, QUERY_TUNING_METHOD,
+ gettext_noop("Enables the planner's rechecking of parallel safety in the presence of PARAM_EXEC params (for correlated subqueries)."),
+ NULL,
+ GUC_EXPLAIN
+ },
+ &enable_parallel_params_recheck,
+ true,
+ NULL, NULL, NULL
+ },
{
{"enable_seqscan", PGC_USERSET, QUERY_TUNING_METHOD,
gettext_noop("Enables the planner's use of sequential-scan plans."),
diff --git a/src/include/nodes/pathnodes.h b/src/include/nodes/pathnodes.h
index a65bda7e3c..2ecbb016a2 100644
--- a/src/include/nodes/pathnodes.h
+++ b/src/include/nodes/pathnodes.h
@@ -682,6 +682,7 @@ typedef struct RelOptInfo
bool consider_startup; /* keep cheap-startup-cost paths? */
bool consider_param_startup; /* ditto, for parameterized paths? */
bool consider_parallel; /* consider parallel paths? */
+ bool consider_parallel_rechecking_params; /* consider parallel paths? */
/* default result targetlist for Paths scanning this relation */
struct PathTarget *reltarget; /* list of Vars/Exprs, cost, width */
@@ -1178,6 +1179,7 @@ typedef struct Path
bool parallel_aware; /* engage parallel-aware logic? */
bool parallel_safe; /* OK to use as part of parallel plan? */
+ bool parallel_safe_ignoring_params; /* OK to use as part of parallel plan if worker context provides params? */
int parallel_workers; /* desired # of workers; 0 = not parallel */
/* estimated size/costs for path (see costsize.c for more info) */
@@ -2464,7 +2466,7 @@ typedef struct MinMaxAggInfo
* for conflicting purposes.
*
* In addition, PARAM_EXEC slots are assigned for Params representing outputs
- * from subplans (values that are setParam items for those subplans). These
+ * from subplans (values that are setParam items for those subplans). [TODO: is this true, or only for init plans?] These
* IDs need not be tracked via PlannerParamItems, since we do not need any
* duplicate-elimination nor later processing of the represented expressions.
* Instead, we just record the assignment of the slot number by appending to
@@ -2583,6 +2585,7 @@ typedef struct
/* Data which may differ across partitions. */
bool target_parallel_safe;
+ bool target_parallel_safe_ignoring_params;
Node *havingQual;
List *targetList;
PartitionwiseAggregateType patype;
diff --git a/src/include/nodes/plannodes.h b/src/include/nodes/plannodes.h
index d671328dfd..b36def462b 100644
--- a/src/include/nodes/plannodes.h
+++ b/src/include/nodes/plannodes.h
@@ -128,6 +128,7 @@ typedef struct Plan
*/
bool parallel_aware; /* engage parallel-aware logic? */
bool parallel_safe; /* OK to use as part of parallel plan? */
+ bool parallel_safe_ignoring_params; /* OK to use as part of parallel plan if worker context provides params? */
/*
* information needed for asynchronous execution
diff --git a/src/include/nodes/primnodes.h b/src/include/nodes/primnodes.h
index 9ae851d847..279a8e106b 100644
--- a/src/include/nodes/primnodes.h
+++ b/src/include/nodes/primnodes.h
@@ -754,6 +754,7 @@ typedef struct SubPlan
* spec result is UNKNOWN; this allows much
* simpler handling of null values */
bool parallel_safe; /* is the subplan parallel-safe? */
+ bool parallel_safe_ignoring_params; /* is the subplan parallel-safe when params are provided by the worker context? */
/* Note: parallel_safe does not consider contents of testexpr or args */
/* Information for passing params into and out of the subselect: */
/* setParam and parParam are lists of integers (param IDs) */
diff --git a/src/include/optimizer/clauses.h b/src/include/optimizer/clauses.h
index 0673887a85..df01be2c61 100644
--- a/src/include/optimizer/clauses.h
+++ b/src/include/optimizer/clauses.h
@@ -16,6 +16,8 @@
#include "nodes/pathnodes.h"
+extern PGDLLIMPORT bool enable_parallel_params_recheck;
+
typedef struct
{
int numWindowFuncs; /* total number of WindowFuncs found */
@@ -33,7 +35,7 @@ extern double expression_returns_set_rows(PlannerInfo *root, Node *clause);
extern bool contain_subplans(Node *clause);
extern char max_parallel_hazard(Query *parse);
-extern bool is_parallel_safe(PlannerInfo *root, Node *node);
+extern bool is_parallel_safe(PlannerInfo *root, Node *node, bool *safe_ignoring_params);
extern bool contain_nonstrict_functions(Node *clause);
extern bool contain_exec_param(Node *clause, List *param_ids);
extern bool contain_leaked_vars(Node *clause);
diff --git a/src/test/regress/expected/incremental_sort.out b/src/test/regress/expected/incremental_sort.out
index 545e301e48..8f9ca05e60 100644
--- a/src/test/regress/expected/incremental_sort.out
+++ b/src/test/regress/expected/incremental_sort.out
@@ -1614,16 +1614,16 @@ from tenk1 t, generate_series(1, 1000);
QUERY PLAN
---------------------------------------------------------------------------------
Unique
- -> Sort
- Sort Key: t.unique1, ((SubPlan 1))
- -> Gather
- Workers Planned: 2
+ -> Gather Merge
+ Workers Planned: 2
+ -> Sort
+ Sort Key: t.unique1, ((SubPlan 1))
-> Nested Loop
-> Parallel Index Only Scan using tenk1_unique1 on tenk1 t
-> Function Scan on generate_series
- SubPlan 1
- -> Index Only Scan using tenk1_unique1 on tenk1
- Index Cond: (unique1 = t.unique1)
+ SubPlan 1
+ -> Index Only Scan using tenk1_unique1 on tenk1
+ Index Cond: (unique1 = t.unique1)
(11 rows)
explain (costs off) select
@@ -1633,16 +1633,16 @@ from tenk1 t, generate_series(1, 1000)
order by 1, 2;
QUERY PLAN
---------------------------------------------------------------------------
- Sort
- Sort Key: t.unique1, ((SubPlan 1))
- -> Gather
- Workers Planned: 2
+ Gather Merge
+ Workers Planned: 2
+ -> Sort
+ Sort Key: t.unique1, ((SubPlan 1))
-> Nested Loop
-> Parallel Index Only Scan using tenk1_unique1 on tenk1 t
-> Function Scan on generate_series
- SubPlan 1
- -> Index Only Scan using tenk1_unique1 on tenk1
- Index Cond: (unique1 = t.unique1)
+ SubPlan 1
+ -> Index Only Scan using tenk1_unique1 on tenk1
+ Index Cond: (unique1 = t.unique1)
(10 rows)
-- Parallel sort but with expression not available until the upper rel.
diff --git a/src/test/regress/expected/select_parallel.out b/src/test/regress/expected/select_parallel.out
index 224a1da2af..e6f2453a1f 100644
--- a/src/test/regress/expected/select_parallel.out
+++ b/src/test/regress/expected/select_parallel.out
@@ -311,6 +311,131 @@ select count(*) from tenk1 where (two, four) not in
10000
(1 row)
+-- test parallel plans for queries containing correlated subplans
+-- where the subplan only needs params available from the current
+-- worker's scan.
+explain (costs off, verbose) select
+ (select t.unique1 from tenk1 where tenk1.unique1 = t.unique1)
+ from tenk1 t, generate_series(1, 10);
+ QUERY PLAN
+----------------------------------------------------------------------------
+ Gather
+ Output: ((SubPlan 1))
+ Workers Planned: 4
+ -> Nested Loop
+ Output: (SubPlan 1)
+ -> Parallel Index Only Scan using tenk1_unique1 on public.tenk1 t
+ Output: t.unique1
+ -> Function Scan on pg_catalog.generate_series
+ Output: generate_series.generate_series
+ Function Call: generate_series(1, 10)
+ SubPlan 1
+ -> Index Only Scan using tenk1_unique1 on public.tenk1
+ Output: t.unique1
+ Index Cond: (tenk1.unique1 = t.unique1)
+(14 rows)
+
+explain (costs off, verbose) select
+ (select t.unique1 from tenk1 where tenk1.unique1 = t.unique1)
+ from tenk1 t;
+ QUERY PLAN
+----------------------------------------------------------------------
+ Gather
+ Output: ((SubPlan 1))
+ Workers Planned: 4
+ -> Parallel Index Only Scan using tenk1_unique1 on public.tenk1 t
+ Output: (SubPlan 1)
+ SubPlan 1
+ -> Index Only Scan using tenk1_unique1 on public.tenk1
+ Output: t.unique1
+ Index Cond: (tenk1.unique1 = t.unique1)
+(9 rows)
+
+explain (analyze, costs off, summary off, verbose, timing off) select
+ (select t.unique1 from tenk1 where tenk1.unique1 = t.unique1)
+ from tenk1 t
+ limit 1;
+ QUERY PLAN
+----------------------------------------------------------------------------------------------------
+ Limit (actual rows=1 loops=1)
+ Output: ((SubPlan 1))
+ -> Gather (actual rows=1 loops=1)
+ Output: ((SubPlan 1))
+ Workers Planned: 4
+ Workers Launched: 4
+ -> Parallel Index Only Scan using tenk1_unique1 on public.tenk1 t (actual rows=1 loops=5)
+ Output: (SubPlan 1)
+ Heap Fetches: 0
+ Worker 0: actual rows=1 loops=1
+ Worker 1: actual rows=1 loops=1
+ Worker 2: actual rows=1 loops=1
+ Worker 3: actual rows=1 loops=1
+ SubPlan 1
+ -> Index Only Scan using tenk1_unique1 on public.tenk1 (actual rows=1 loops=5)
+ Output: t.unique1
+ Index Cond: (tenk1.unique1 = t.unique1)
+ Heap Fetches: 0
+ Worker 0: actual rows=1 loops=1
+ Worker 1: actual rows=1 loops=1
+ Worker 2: actual rows=1 loops=1
+ Worker 3: actual rows=1 loops=1
+(22 rows)
+
+explain (costs off, verbose) select t.unique1
+ from tenk1 t
+ where t.unique1 = (select t.unique1 from tenk1 where tenk1.unique1 = t.unique1);
+ QUERY PLAN
+----------------------------------------------------------------------
+ Gather
+ Output: t.unique1
+ Workers Planned: 4
+ -> Parallel Index Only Scan using tenk1_unique1 on public.tenk1 t
+ Output: t.unique1
+ Filter: (t.unique1 = (SubPlan 1))
+ SubPlan 1
+ -> Index Only Scan using tenk1_unique1 on public.tenk1
+ Output: t.unique1
+ Index Cond: (tenk1.unique1 = t.unique1)
+(10 rows)
+
+explain (costs off, verbose) select *
+ from tenk1 t
+ order by (select t.unique1 from tenk1 where tenk1.unique1 = t.unique1);
+ QUERY PLAN
+----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
+ Gather Merge
+ Output: t.unique1, t.unique2, t.two, t.four, t.ten, t.twenty, t.hundred, t.thousand, t.twothousand, t.fivethous, t.tenthous, t.odd, t.even, t.stringu1, t.stringu2, t.string4, ((SubPlan 1))
+ Workers Planned: 4
+ -> Sort
+ Output: t.unique1, t.unique2, t.two, t.four, t.ten, t.twenty, t.hundred, t.thousand, t.twothousand, t.fivethous, t.tenthous, t.odd, t.even, t.stringu1, t.stringu2, t.string4, ((SubPlan 1))
+ Sort Key: ((SubPlan 1))
+ -> Parallel Seq Scan on public.tenk1 t
+ Output: t.unique1, t.unique2, t.two, t.four, t.ten, t.twenty, t.hundred, t.thousand, t.twothousand, t.fivethous, t.tenthous, t.odd, t.even, t.stringu1, t.stringu2, t.string4, (SubPlan 1)
+ SubPlan 1
+ -> Index Only Scan using tenk1_unique1 on public.tenk1
+ Output: t.unique1
+ Index Cond: (tenk1.unique1 = t.unique1)
+(12 rows)
+
+-- test subplan in join/lateral join
+explain (costs off, verbose, timing off) select t.unique1, l.*
+ from tenk1 t
+ join lateral (
+ select (select t.unique1 from tenk1 where tenk1.unique1 = t.unique1 offset 0)
+ ) l on true;
+ QUERY PLAN
+----------------------------------------------------------------------
+ Gather
+ Output: t.unique1, ((SubPlan 1))
+ Workers Planned: 4
+ -> Parallel Index Only Scan using tenk1_unique1 on public.tenk1 t
+ Output: t.unique1, (SubPlan 1)
+ SubPlan 1
+ -> Index Only Scan using tenk1_unique1 on public.tenk1
+ Output: t.unique1
+ Index Cond: (tenk1.unique1 = t.unique1)
+(9 rows)
+
-- this is not parallel-safe due to use of random() within SubLink's testexpr:
explain (costs off)
select * from tenk1 where (unique1 + random())::integer not in
@@ -1169,6 +1294,18 @@ EXECUTE pstmt('1', make_some_array(1,2));
DEALLOCATE pstmt;
-- test interaction between subquery and partial_paths
+-- this plan changes to using a non-parallel index only
+-- scan on tenk1_unique1 (the parallel version of the subquery scan
+-- is cheaper, but only by ~30, and cost comparison treats them as equal
+-- since the costs are so large) because set_rel_consider_parallel
+-- called from make_one_rel sees the subplan as parallel safe now
+-- (in context it now knows the params are actually parallel safe).
+-- Because of that the non-parallel index path is now parallel_safe=true,
+-- therefore it wins the COSTS_EQUAL comparison in add_path.
+-- Perhaps any is_parallel_safe calls made for the purpose of determining
+-- consider_parallel should disable that behavior? It's not clear which is
+-- correct.
+set enable_parallel_params_recheck = off;
CREATE VIEW tenk1_vw_sec WITH (security_barrier) AS SELECT * FROM tenk1;
EXPLAIN (COSTS OFF)
SELECT 1 FROM tenk1_vw_sec
diff --git a/src/test/regress/expected/sysviews.out b/src/test/regress/expected/sysviews.out
index 0bb558d93c..22fee51455 100644
--- a/src/test/regress/expected/sysviews.out
+++ b/src/test/regress/expected/sysviews.out
@@ -108,6 +108,7 @@ select name, setting from pg_settings where name like 'enable%';
enable_nestloop | on
enable_parallel_append | on
enable_parallel_hash | on
+ enable_parallel_params_recheck | on
enable_partition_pruning | on
enable_partitionwise_aggregate | off
enable_partitionwise_join | off
@@ -115,7 +116,7 @@ select name, setting from pg_settings where name like 'enable%';
enable_seqscan | on
enable_sort | on
enable_tidscan | on
-(20 rows)
+(21 rows)
-- Test that the pg_timezone_names and pg_timezone_abbrevs views are
-- more-or-less working. We can't test their contents in any great detail
diff --git a/src/test/regress/sql/select_parallel.sql b/src/test/regress/sql/select_parallel.sql
index f656764fa9..55a3bd9025 100644
--- a/src/test/regress/sql/select_parallel.sql
+++ b/src/test/regress/sql/select_parallel.sql
@@ -111,6 +111,31 @@ explain (costs off)
(select hundred, thousand from tenk2 where thousand > 100);
select count(*) from tenk1 where (two, four) not in
(select hundred, thousand from tenk2 where thousand > 100);
+-- test parallel plans for queries containing correlated subplans
+-- where the subplan only needs params available from the current
+-- worker's scan.
+explain (costs off, verbose) select
+ (select t.unique1 from tenk1 where tenk1.unique1 = t.unique1)
+ from tenk1 t, generate_series(1, 10);
+explain (costs off, verbose) select
+ (select t.unique1 from tenk1 where tenk1.unique1 = t.unique1)
+ from tenk1 t;
+explain (analyze, costs off, summary off, verbose, timing off) select
+ (select t.unique1 from tenk1 where tenk1.unique1 = t.unique1)
+ from tenk1 t
+ limit 1;
+explain (costs off, verbose) select t.unique1
+ from tenk1 t
+ where t.unique1 = (select t.unique1 from tenk1 where tenk1.unique1 = t.unique1);
+explain (costs off, verbose) select *
+ from tenk1 t
+ order by (select t.unique1 from tenk1 where tenk1.unique1 = t.unique1);
+-- test subplan in join/lateral join
+explain (costs off, verbose, timing off) select t.unique1, l.*
+ from tenk1 t
+ join lateral (
+ select (select t.unique1 from tenk1 where tenk1.unique1 = t.unique1 offset 0)
+ ) l on true;
-- this is not parallel-safe due to use of random() within SubLink's testexpr:
explain (costs off)
select * from tenk1 where (unique1 + random())::integer not in
@@ -452,6 +477,18 @@ EXECUTE pstmt('1', make_some_array(1,2));
DEALLOCATE pstmt;
-- test interaction between subquery and partial_paths
+-- this plan changes to using a non-parallel index only
+-- scan on tenk1_unique1 (the parallel version of the subquery scan
+-- is cheaper, but only by ~30, and cost comparison treats them as equal
+-- since the costs are so large) because set_rel_consider_parallel
+-- called from make_one_rel sees the subplan as parallel safe now
+-- (in context it now knows the params are actually parallel safe).
+-- Because of that the non-parallel index path is now parallel_safe=true,
+-- therefore it wins the COSTS_EQUAL comparison in add_path.
+-- Perhaps any is_parallel_safe calls made for the purpose of determining
+-- consider_parallel should disable that behavior? It's not clear which is
+-- correct.
+set enable_parallel_params_recheck = off;
CREATE VIEW tenk1_vw_sec WITH (security_barrier) AS SELECT * FROM tenk1;
EXPLAIN (COSTS OFF)
SELECT 1 FROM tenk1_vw_sec
--
2.20.1
[application/octet-stream] v1-0001-Allow-parallel-LATERAL-subqueries-with-LIMIT-OFFS.patch (3.5K, ../../CAAaqYe_x1u3V4uPiv=dJ=k2EJ7txhdq6yexJDkYZ1x1pu0QwcQ@mail.gmail.com/4-v1-0001-Allow-parallel-LATERAL-subqueries-with-LIMIT-OFFS.patch)
download | inline diff:
From 4f51cf83caaffcbe2500898d7d939c885c0c352c Mon Sep 17 00:00:00 2001
From: jcoleman <[email protected]>
Date: Mon, 30 Nov 2020 11:36:35 -0500
Subject: [PATCH v1 1/3] Allow parallel LATERAL subqueries with LIMIT/OFFSET
The code that determined whether or not a rel should be considered for
parallel query excluded subqueries with LIMIT/OFFSET. That's correct in
the general case: as the comment notes that'd mean we have to guarantee
ordering (and claims it's not worth checking that) for results to be
consistent across workers. However there's a simpler case that hasn't
been considered: LATERAL subqueries with LIMIT/OFFSET don't fall under
the same reasoning since they're executed (when not converted to a JOIN)
per tuple anyway, so consistency of results across workers isn't a
factor.
---
src/backend/optimizer/path/allpaths.c | 4 +++-
src/test/regress/expected/select_parallel.out | 15 +++++++++++++++
src/test/regress/sql/select_parallel.sql | 6 ++++++
3 files changed, 24 insertions(+), 1 deletion(-)
diff --git a/src/backend/optimizer/path/allpaths.c b/src/backend/optimizer/path/allpaths.c
index 353454b183..45e37590d8 100644
--- a/src/backend/optimizer/path/allpaths.c
+++ b/src/backend/optimizer/path/allpaths.c
@@ -682,11 +682,13 @@ set_rel_consider_parallel(PlannerInfo *root, RelOptInfo *rel,
* inconsistent results at the top-level. (In some cases, where
* the result is ordered, we could relax this restriction. But it
* doesn't currently seem worth expending extra effort to do so.)
+ * LATERAL is an exception: LIMIT/OFFSET is safe to execute within
+ * workers since the sub-select is executed per tuple
*/
{
Query *subquery = castNode(Query, rte->subquery);
- if (limit_needed(subquery))
+ if (!rte->lateral && limit_needed(subquery))
return;
}
break;
diff --git a/src/test/regress/expected/select_parallel.out b/src/test/regress/expected/select_parallel.out
index 05ebcb284a..224a1da2af 100644
--- a/src/test/regress/expected/select_parallel.out
+++ b/src/test/regress/expected/select_parallel.out
@@ -1040,6 +1040,21 @@ explain (costs off)
Filter: (stringu1 ~~ '%AAAA'::text)
(11 rows)
+-- ...unless it's LATERAL
+savepoint settings;
+set parallel_tuple_cost=0;
+explain (costs off) select t.unique1 from tenk1 t
+join lateral (select t.unique1 from tenk1 offset 0) l on true;
+ QUERY PLAN
+---------------------------------------------------------------------
+ Gather
+ Workers Planned: 4
+ -> Nested Loop
+ -> Parallel Index Only Scan using tenk1_unique1 on tenk1 t
+ -> Index Only Scan using tenk1_hundred on tenk1
+(5 rows)
+
+rollback to savepoint settings;
-- to increase the parallel query test coverage
SAVEPOINT settings;
SET LOCAL force_parallel_mode = 1;
diff --git a/src/test/regress/sql/select_parallel.sql b/src/test/regress/sql/select_parallel.sql
index d31e290ec2..f656764fa9 100644
--- a/src/test/regress/sql/select_parallel.sql
+++ b/src/test/regress/sql/select_parallel.sql
@@ -390,6 +390,12 @@ explain (costs off, verbose)
explain (costs off)
select * from tenk1 a where two in
(select two from tenk1 b where stringu1 like '%AAAA' limit 3);
+-- ...unless it's LATERAL
+savepoint settings;
+set parallel_tuple_cost=0;
+explain (costs off) select t.unique1 from tenk1 t
+join lateral (select t.unique1 from tenk1 offset 0) l on true;
+rollback to savepoint settings;
-- to increase the parallel query test coverage
SAVEPOINT settings;
--
2.20.1
^ permalink raw reply [nested|flat] 35+ messages in thread
* Re: Parallelize correlated subqueries that execute within each worker
@ 2021-09-01 11:06 Daniel Gustafsson <[email protected]>
parent: James Coleman <[email protected]>
1 sibling, 1 reply; 35+ messages in thread
From: Daniel Gustafsson @ 2021-09-01 11:06 UTC (permalink / raw)
To: James Coleman <[email protected]>; +Cc: pgsql-hackers; Amit Kapila <[email protected]>
> On 7 May 2021, at 18:30, James Coleman <[email protected]> wrote:
> ..here we are now, and I finally have this patch cleaned up
> enough to share.
This patch no longer applies to HEAD, can you please submit a rebased version?
--
Daniel Gustafsson https://vmware.com/
^ permalink raw reply [nested|flat] 35+ messages in thread
* Re: Parallelize correlated subqueries that execute within each worker
@ 2021-09-07 13:16 James Coleman <[email protected]>
parent: Daniel Gustafsson <[email protected]>
0 siblings, 1 reply; 35+ messages in thread
From: James Coleman @ 2021-09-07 13:16 UTC (permalink / raw)
To: Daniel Gustafsson <[email protected]>; +Cc: pgsql-hackers; Amit Kapila <[email protected]>
On Wed, Sep 1, 2021 at 7:06 AM Daniel Gustafsson <[email protected]> wrote:
>
> > On 7 May 2021, at 18:30, James Coleman <[email protected]> wrote:
>
> > ..here we are now, and I finally have this patch cleaned up
> > enough to share.
>
> This patch no longer applies to HEAD, can you please submit a rebased version?
See attached.
Thanks,
James
Attachments:
[application/octet-stream] v2-0001-Allow-parallel-LATERAL-subqueries-with-LIMIT-OFFS.patch (3.5K, ../../CAAaqYe8D2Mpp8T6oqcTRtTBOWVaCA6_1542A1BgBB4xthtXhkw@mail.gmail.com/2-v2-0001-Allow-parallel-LATERAL-subqueries-with-LIMIT-OFFS.patch)
download | inline diff:
From 7ba602847a13fbf7c87aab3651b4304ffba5e9e6 Mon Sep 17 00:00:00 2001
From: jcoleman <[email protected]>
Date: Mon, 30 Nov 2020 11:36:35 -0500
Subject: [PATCH v2 1/3] Allow parallel LATERAL subqueries with LIMIT/OFFSET
The code that determined whether or not a rel should be considered for
parallel query excluded subqueries with LIMIT/OFFSET. That's correct in
the general case: as the comment notes that'd mean we have to guarantee
ordering (and claims it's not worth checking that) for results to be
consistent across workers. However there's a simpler case that hasn't
been considered: LATERAL subqueries with LIMIT/OFFSET don't fall under
the same reasoning since they're executed (when not converted to a JOIN)
per tuple anyway, so consistency of results across workers isn't a
factor.
---
src/backend/optimizer/path/allpaths.c | 4 +++-
src/test/regress/expected/select_parallel.out | 15 +++++++++++++++
src/test/regress/sql/select_parallel.sql | 6 ++++++
3 files changed, 24 insertions(+), 1 deletion(-)
diff --git a/src/backend/optimizer/path/allpaths.c b/src/backend/optimizer/path/allpaths.c
index 296dd75c1b..1363f1bc6c 100644
--- a/src/backend/optimizer/path/allpaths.c
+++ b/src/backend/optimizer/path/allpaths.c
@@ -682,11 +682,13 @@ set_rel_consider_parallel(PlannerInfo *root, RelOptInfo *rel,
* inconsistent results at the top-level. (In some cases, where
* the result is ordered, we could relax this restriction. But it
* doesn't currently seem worth expending extra effort to do so.)
+ * LATERAL is an exception: LIMIT/OFFSET is safe to execute within
+ * workers since the sub-select is executed per tuple
*/
{
Query *subquery = castNode(Query, rte->subquery);
- if (limit_needed(subquery))
+ if (!rte->lateral && limit_needed(subquery))
return;
}
break;
diff --git a/src/test/regress/expected/select_parallel.out b/src/test/regress/expected/select_parallel.out
index 4ea1aa7dfd..2303f70d6e 100644
--- a/src/test/regress/expected/select_parallel.out
+++ b/src/test/regress/expected/select_parallel.out
@@ -1040,6 +1040,21 @@ explain (costs off)
Filter: (stringu1 ~~ '%AAAA'::text)
(11 rows)
+-- ...unless it's LATERAL
+savepoint settings;
+set parallel_tuple_cost=0;
+explain (costs off) select t.unique1 from tenk1 t
+join lateral (select t.unique1 from tenk1 offset 0) l on true;
+ QUERY PLAN
+---------------------------------------------------------------------
+ Gather
+ Workers Planned: 4
+ -> Nested Loop
+ -> Parallel Index Only Scan using tenk1_unique1 on tenk1 t
+ -> Index Only Scan using tenk1_hundred on tenk1
+(5 rows)
+
+rollback to savepoint settings;
-- to increase the parallel query test coverage
SAVEPOINT settings;
SET LOCAL force_parallel_mode = 1;
diff --git a/src/test/regress/sql/select_parallel.sql b/src/test/regress/sql/select_parallel.sql
index f924731248..019e17e751 100644
--- a/src/test/regress/sql/select_parallel.sql
+++ b/src/test/regress/sql/select_parallel.sql
@@ -390,6 +390,12 @@ explain (costs off, verbose)
explain (costs off)
select * from tenk1 a where two in
(select two from tenk1 b where stringu1 like '%AAAA' limit 3);
+-- ...unless it's LATERAL
+savepoint settings;
+set parallel_tuple_cost=0;
+explain (costs off) select t.unique1 from tenk1 t
+join lateral (select t.unique1 from tenk1 offset 0) l on true;
+rollback to savepoint settings;
-- to increase the parallel query test coverage
SAVEPOINT settings;
--
2.20.1
[application/octet-stream] v2-0002-Parallel-query-support-for-basic-correlated-subqu.patch (75.3K, ../../CAAaqYe8D2Mpp8T6oqcTRtTBOWVaCA6_1542A1BgBB4xthtXhkw@mail.gmail.com/3-v2-0002-Parallel-query-support-for-basic-correlated-subqu.patch)
download | inline diff:
From 41ce0d022fb0dcccd12fa713a07c139452d9c763 Mon Sep 17 00:00:00 2001
From: jcoleman <[email protected]>
Date: Fri, 27 Nov 2020 18:44:30 -0500
Subject: [PATCH v2 2/3] Parallel query support for basic correlated subqueries
Not all Params are inherently parallel-unsafe, but we can't know whether
they're parallel-safe up-front: we need contextual information for a
given path shape. Here we delay the final determination of whether or
not a Param is parallel-safe by initially verifying that it is minimally
parallel-safe for things that are inherent (e.g., no parallel-unsafe
functions or relations involved) and later re-checking that a given
usage is contextually safe (e.g., the Param is for correlation that can
happen entirely within a parallel worker (as opposed to needing to pass
values between workers).
---
doc/src/sgml/parallel.sgml | 3 +-
src/backend/nodes/copyfuncs.c | 2 +
src/backend/nodes/equalfuncs.c | 1 +
src/backend/nodes/outfuncs.c | 3 +
src/backend/nodes/readfuncs.c | 2 +
src/backend/optimizer/path/allpaths.c | 61 +++++--
src/backend/optimizer/path/equivclass.c | 4 +-
src/backend/optimizer/path/indxpath.c | 20 ++-
src/backend/optimizer/path/joinpath.c | 21 ++-
src/backend/optimizer/plan/createplan.c | 2 +
src/backend/optimizer/plan/planmain.c | 2 +-
src/backend/optimizer/plan/planner.c | 155 +++++++++++++++---
src/backend/optimizer/plan/subselect.c | 21 ++-
src/backend/optimizer/prep/prepunion.c | 1 +
src/backend/optimizer/util/clauses.c | 113 ++++++++++---
src/backend/optimizer/util/pathnode.c | 36 +++-
src/backend/optimizer/util/relnode.c | 30 +++-
src/backend/utils/misc/guc.c | 11 ++
src/include/nodes/pathnodes.h | 5 +-
src/include/nodes/plannodes.h | 1 +
src/include/nodes/primnodes.h | 1 +
src/include/optimizer/clauses.h | 4 +-
.../regress/expected/incremental_sort.out | 28 ++--
src/test/regress/expected/select_parallel.out | 137 ++++++++++++++++
src/test/regress/expected/sysviews.out | 3 +-
src/test/regress/sql/select_parallel.sql | 37 +++++
26 files changed, 604 insertions(+), 100 deletions(-)
diff --git a/doc/src/sgml/parallel.sgml b/doc/src/sgml/parallel.sgml
index 13479d7e5e..a651a9fe73 100644
--- a/doc/src/sgml/parallel.sgml
+++ b/doc/src/sgml/parallel.sgml
@@ -517,7 +517,8 @@ EXPLAIN SELECT * FROM pgbench_accounts WHERE filler LIKE '%x%';
<listitem>
<para>
- Plan nodes that reference a correlated <literal>SubPlan</literal>.
+ Plan nodes thatreference a correlated <literal>SubPlan</literal> where
+ the result is shared between workers.
</para>
</listitem>
</itemizedlist>
diff --git a/src/backend/nodes/copyfuncs.c b/src/backend/nodes/copyfuncs.c
index 38251c2b8e..4042cef2ea 100644
--- a/src/backend/nodes/copyfuncs.c
+++ b/src/backend/nodes/copyfuncs.c
@@ -124,6 +124,7 @@ CopyPlanFields(const Plan *from, Plan *newnode)
COPY_SCALAR_FIELD(parallel_aware);
COPY_SCALAR_FIELD(parallel_safe);
COPY_SCALAR_FIELD(async_capable);
+ COPY_SCALAR_FIELD(parallel_safe_ignoring_params);
COPY_SCALAR_FIELD(plan_node_id);
COPY_NODE_FIELD(targetlist);
COPY_NODE_FIELD(qual);
@@ -1767,6 +1768,7 @@ _copySubPlan(const SubPlan *from)
COPY_SCALAR_FIELD(useHashTable);
COPY_SCALAR_FIELD(unknownEqFalse);
COPY_SCALAR_FIELD(parallel_safe);
+ COPY_SCALAR_FIELD(parallel_safe_ignoring_params);
COPY_NODE_FIELD(setParam);
COPY_NODE_FIELD(parParam);
COPY_NODE_FIELD(args);
diff --git a/src/backend/nodes/equalfuncs.c b/src/backend/nodes/equalfuncs.c
index 8a1762000c..482063c066 100644
--- a/src/backend/nodes/equalfuncs.c
+++ b/src/backend/nodes/equalfuncs.c
@@ -465,6 +465,7 @@ _equalSubPlan(const SubPlan *a, const SubPlan *b)
COMPARE_SCALAR_FIELD(useHashTable);
COMPARE_SCALAR_FIELD(unknownEqFalse);
COMPARE_SCALAR_FIELD(parallel_safe);
+ COMPARE_SCALAR_FIELD(parallel_safe_ignoring_params);
COMPARE_NODE_FIELD(setParam);
COMPARE_NODE_FIELD(parParam);
COMPARE_NODE_FIELD(args);
diff --git a/src/backend/nodes/outfuncs.c b/src/backend/nodes/outfuncs.c
index 87561cbb6f..42dbb05db5 100644
--- a/src/backend/nodes/outfuncs.c
+++ b/src/backend/nodes/outfuncs.c
@@ -334,6 +334,7 @@ _outPlanInfo(StringInfo str, const Plan *node)
WRITE_BOOL_FIELD(parallel_aware);
WRITE_BOOL_FIELD(parallel_safe);
WRITE_BOOL_FIELD(async_capable);
+ WRITE_BOOL_FIELD(parallel_safe_ignoring_params);
WRITE_INT_FIELD(plan_node_id);
WRITE_NODE_FIELD(targetlist);
WRITE_NODE_FIELD(qual);
@@ -1374,6 +1375,7 @@ _outSubPlan(StringInfo str, const SubPlan *node)
WRITE_BOOL_FIELD(useHashTable);
WRITE_BOOL_FIELD(unknownEqFalse);
WRITE_BOOL_FIELD(parallel_safe);
+ WRITE_BOOL_FIELD(parallel_safe_ignoring_params);
WRITE_NODE_FIELD(setParam);
WRITE_NODE_FIELD(parParam);
WRITE_NODE_FIELD(args);
@@ -1772,6 +1774,7 @@ _outPathInfo(StringInfo str, const Path *node)
outBitmapset(str, NULL);
WRITE_BOOL_FIELD(parallel_aware);
WRITE_BOOL_FIELD(parallel_safe);
+ WRITE_BOOL_FIELD(parallel_safe_ignoring_params);
WRITE_INT_FIELD(parallel_workers);
WRITE_FLOAT_FIELD(rows, "%.0f");
WRITE_FLOAT_FIELD(startup_cost, "%.2f");
diff --git a/src/backend/nodes/readfuncs.c b/src/backend/nodes/readfuncs.c
index 0dd1ad7dfc..b6598726bb 100644
--- a/src/backend/nodes/readfuncs.c
+++ b/src/backend/nodes/readfuncs.c
@@ -1621,6 +1621,7 @@ ReadCommonPlan(Plan *local_node)
READ_BOOL_FIELD(parallel_aware);
READ_BOOL_FIELD(parallel_safe);
READ_BOOL_FIELD(async_capable);
+ READ_BOOL_FIELD(parallel_safe_ignoring_params);
READ_INT_FIELD(plan_node_id);
READ_NODE_FIELD(targetlist);
READ_NODE_FIELD(qual);
@@ -2615,6 +2616,7 @@ _readSubPlan(void)
READ_BOOL_FIELD(useHashTable);
READ_BOOL_FIELD(unknownEqFalse);
READ_BOOL_FIELD(parallel_safe);
+ READ_BOOL_FIELD(parallel_safe_ignoring_params);
READ_NODE_FIELD(setParam);
READ_NODE_FIELD(parParam);
READ_NODE_FIELD(args);
diff --git a/src/backend/optimizer/path/allpaths.c b/src/backend/optimizer/path/allpaths.c
index 1363f1bc6c..5ab6d0e23f 100644
--- a/src/backend/optimizer/path/allpaths.c
+++ b/src/backend/optimizer/path/allpaths.c
@@ -556,7 +556,8 @@ set_rel_pathlist(PlannerInfo *root, RelOptInfo *rel,
* (see grouping_planner).
*/
if (rel->reloptkind == RELOPT_BASEREL &&
- bms_membership(root->all_baserels) != BMS_SINGLETON)
+ bms_membership(root->all_baserels) != BMS_SINGLETON
+ && (rel->subplan_params == NIL || rte->rtekind != RTE_SUBQUERY))
generate_useful_gather_paths(root, rel, false);
/* Now find the cheapest of the paths for this rel */
@@ -592,6 +593,9 @@ static void
set_rel_consider_parallel(PlannerInfo *root, RelOptInfo *rel,
RangeTblEntry *rte)
{
+ bool parallel_safe;
+ bool parallel_safe_except_in_params;
+
/*
* The flag has previously been initialized to false, so we can just
* return if it becomes clear that we can't safely set it.
@@ -632,7 +636,7 @@ set_rel_consider_parallel(PlannerInfo *root, RelOptInfo *rel,
if (proparallel != PROPARALLEL_SAFE)
return;
- if (!is_parallel_safe(root, (Node *) rte->tablesample->args))
+ if (!is_parallel_safe(root, (Node *) rte->tablesample->args, NULL))
return;
}
@@ -700,7 +704,7 @@ set_rel_consider_parallel(PlannerInfo *root, RelOptInfo *rel,
case RTE_FUNCTION:
/* Check for parallel-restricted functions. */
- if (!is_parallel_safe(root, (Node *) rte->functions))
+ if (!is_parallel_safe(root, (Node *) rte->functions, NULL))
return;
break;
@@ -710,7 +714,7 @@ set_rel_consider_parallel(PlannerInfo *root, RelOptInfo *rel,
case RTE_VALUES:
/* Check for parallel-restricted functions. */
- if (!is_parallel_safe(root, (Node *) rte->values_lists))
+ if (!is_parallel_safe(root, (Node *) rte->values_lists, NULL))
return;
break;
@@ -747,18 +751,28 @@ set_rel_consider_parallel(PlannerInfo *root, RelOptInfo *rel,
* outer join clauses work correctly. It would likely break equivalence
* classes, too.
*/
- if (!is_parallel_safe(root, (Node *) rel->baserestrictinfo))
- return;
+ parallel_safe = is_parallel_safe(root, (Node *) rel->baserestrictinfo,
+ ¶llel_safe_except_in_params);
/*
* Likewise, if the relation's outputs are not parallel-safe, give up.
* (Usually, they're just Vars, but sometimes they're not.)
*/
- if (!is_parallel_safe(root, (Node *) rel->reltarget->exprs))
- return;
+ if (parallel_safe || parallel_safe_except_in_params)
+ {
+ bool target_parallel_safe;
+ bool target_parallel_safe_ignoring_params = false;
+
+ target_parallel_safe = is_parallel_safe(root,
+ (Node *) rel->reltarget->exprs,
+ &target_parallel_safe_ignoring_params);
+ parallel_safe = parallel_safe && target_parallel_safe;
+ parallel_safe_except_in_params = parallel_safe_except_in_params
+ && target_parallel_safe_ignoring_params;
+ }
- /* We have a winner. */
- rel->consider_parallel = true;
+ rel->consider_parallel = parallel_safe;
+ rel->consider_parallel_rechecking_params = parallel_safe_except_in_params;
}
/*
@@ -2277,9 +2291,21 @@ set_subquery_pathlist(PlannerInfo *root, RelOptInfo *rel,
pathkeys, required_outer));
}
+ /*
+ * XXX: As far as I can tell, the only time partial paths exist here
+ * is when we're going to execute multiple partial parths in parallel
+ * under a gather node (instead of executing paths serially under
+ * an append node). That means that the subquery scan path here
+ * is self-contained at this point -- so by definition it can't be
+ * reliant on lateral relids, which means we'll never have to consider
+ * rechecking params here.
+ */
+ Assert(!(rel->consider_parallel_rechecking_params && rel->partial_pathlist && !rel->consider_parallel));
+
/* If outer rel allows parallelism, do same for partial paths. */
if (rel->consider_parallel && bms_is_empty(required_outer))
{
+
/* If consider_parallel is false, there should be no partial paths. */
Assert(sub_final_rel->consider_parallel ||
sub_final_rel->partial_pathlist == NIL);
@@ -2633,7 +2659,7 @@ generate_gather_paths(PlannerInfo *root, RelOptInfo *rel, bool override_rows)
cheapest_partial_path->rows * cheapest_partial_path->parallel_workers;
simple_gather_path = (Path *)
create_gather_path(root, rel, cheapest_partial_path, rel->reltarget,
- NULL, rowsp);
+ rel->lateral_relids, rowsp);
add_path(rel, simple_gather_path);
/*
@@ -2650,7 +2676,7 @@ generate_gather_paths(PlannerInfo *root, RelOptInfo *rel, bool override_rows)
rows = subpath->rows * subpath->parallel_workers;
path = create_gather_merge_path(root, rel, subpath, rel->reltarget,
- subpath->pathkeys, NULL, rowsp);
+ subpath->pathkeys, rel->lateral_relids, rowsp);
add_path(rel, &path->path);
}
}
@@ -2752,11 +2778,15 @@ generate_useful_gather_paths(PlannerInfo *root, RelOptInfo *rel, bool override_r
double *rowsp = NULL;
List *useful_pathkeys_list = NIL;
Path *cheapest_partial_path = NULL;
+ Relids required_outer = rel->lateral_relids;
/* If there are no partial paths, there's nothing to do here. */
if (rel->partial_pathlist == NIL)
return;
+ if (!bms_is_subset(required_outer, rel->relids))
+ return;
+
/* Should we override the rel's rowcount estimate? */
if (override_rows)
rowsp = &rows;
@@ -2828,7 +2858,7 @@ generate_useful_gather_paths(PlannerInfo *root, RelOptInfo *rel, bool override_r
tmp,
rel->reltarget,
tmp->pathkeys,
- NULL,
+ required_outer,
rowsp);
add_path(rel, &path->path);
@@ -2862,7 +2892,7 @@ generate_useful_gather_paths(PlannerInfo *root, RelOptInfo *rel, bool override_r
tmp,
rel->reltarget,
tmp->pathkeys,
- NULL,
+ required_outer,
rowsp);
add_path(rel, &path->path);
@@ -3041,7 +3071,8 @@ standard_join_search(PlannerInfo *root, int levels_needed, List *initial_rels)
/*
* Except for the topmost scan/join rel, consider gathering
* partial paths. We'll do the same for the topmost scan/join rel
- * once we know the final targetlist (see grouping_planner).
+ * once we know the final targetlist (see
+ * apply_scanjoin_target_to_paths).
*/
if (lev < levels_needed)
generate_useful_gather_paths(root, rel, false);
diff --git a/src/backend/optimizer/path/equivclass.c b/src/backend/optimizer/path/equivclass.c
index 6f1abbe47d..4c176d2d49 100644
--- a/src/backend/optimizer/path/equivclass.c
+++ b/src/backend/optimizer/path/equivclass.c
@@ -897,7 +897,7 @@ find_computable_ec_member(PlannerInfo *root,
* check this last because it's a rather expensive test.
*/
if (require_parallel_safe &&
- !is_parallel_safe(root, (Node *) em->em_expr))
+ !is_parallel_safe(root, (Node *) em->em_expr, NULL))
continue;
return em; /* found usable expression */
@@ -1012,7 +1012,7 @@ relation_can_be_sorted_early(PlannerInfo *root, RelOptInfo *rel,
* check this last because it's a rather expensive test.
*/
if (require_parallel_safe &&
- !is_parallel_safe(root, (Node *) em->em_expr))
+ !is_parallel_safe(root, (Node *) em->em_expr, NULL))
continue;
return true;
diff --git a/src/backend/optimizer/path/indxpath.c b/src/backend/optimizer/path/indxpath.c
index 0e4e00eaf0..262c129ff5 100644
--- a/src/backend/optimizer/path/indxpath.c
+++ b/src/backend/optimizer/path/indxpath.c
@@ -1047,10 +1047,21 @@ build_index_paths(PlannerInfo *root, RelOptInfo *rel,
/*
* If appropriate, consider parallel index scan. We don't allow
* parallel index scan for bitmap index scans.
+ *
+ * XXX: Checking rel->consider_parallel_rechecking_params here resulted
+ * in some odd behavior on:
+ * select (select t.unique1 from tenk1 where tenk1.unique1 = t.unique1) from tenk1 t;
+ * where the total cost on the chosen plan went *up* considering
+ * the extra path.
+ *
+ * Current working theory is that this method is about base relation
+ * scans, and we only want parameterized paths to be parallelized as
+ * companions to existing parallel plans and so don't really care to
+ * consider a separate parallel index scan here.
*/
if (index->amcanparallel &&
- rel->consider_parallel && outer_relids == NULL &&
- scantype != ST_BITMAPSCAN)
+ rel->consider_parallel && outer_relids == NULL &&
+ scantype != ST_BITMAPSCAN)
{
ipath = create_index_path(root, index,
index_clauses,
@@ -1100,9 +1111,10 @@ build_index_paths(PlannerInfo *root, RelOptInfo *rel,
result = lappend(result, ipath);
/* If appropriate, consider parallel index scan */
+ /* XXX: As above here for rel->consider_parallel_rechecking_params? */
if (index->amcanparallel &&
- rel->consider_parallel && outer_relids == NULL &&
- scantype != ST_BITMAPSCAN)
+ rel->consider_parallel && outer_relids == NULL &&
+ scantype != ST_BITMAPSCAN)
{
ipath = create_index_path(root, index,
index_clauses,
diff --git a/src/backend/optimizer/path/joinpath.c b/src/backend/optimizer/path/joinpath.c
index 6407ede12a..f8daa7b265 100644
--- a/src/backend/optimizer/path/joinpath.c
+++ b/src/backend/optimizer/path/joinpath.c
@@ -722,6 +722,7 @@ try_partial_nestloop_path(PlannerInfo *root,
else
outerrelids = outerrel->relids;
+ /* TODO: recheck parallel safety here? */
if (!bms_is_subset(inner_paramrels, outerrelids))
return;
}
@@ -1746,16 +1747,24 @@ match_unsorted_outer(PlannerInfo *root,
* partial path and the joinrel is parallel-safe. However, we can't
* handle JOIN_UNIQUE_OUTER, because the outer path will be partial, and
* therefore we won't be able to properly guarantee uniqueness. Nor can
- * we handle joins needing lateral rels, since partial paths must not be
- * parameterized. Similarly, we can't handle JOIN_FULL and JOIN_RIGHT,
- * because they can produce false null extended rows.
+ * we handle JOIN_FULL and JOIN_RIGHT, because they can produce false null
+ * extended rows.
+ *
+ * Partial paths may only have parameters in limited cases
+ * where the parameterization is fully satisfied without sharing state
+ * between workers, so we only allow lateral rels on inputs to the join
+ * if the resulting join contains no lateral rels, the inner rel's laterals
+ * are fully satisfied by the outer rel, and the outer rel doesn't depend
+ * on the inner rel to produce any laterals.
*/
if (joinrel->consider_parallel &&
save_jointype != JOIN_UNIQUE_OUTER &&
save_jointype != JOIN_FULL &&
save_jointype != JOIN_RIGHT &&
outerrel->partial_pathlist != NIL &&
- bms_is_empty(joinrel->lateral_relids))
+ bms_is_empty(joinrel->lateral_relids) &&
+ bms_is_subset(innerrel->lateral_relids, outerrel->relids) &&
+ (bms_is_empty(outerrel->lateral_relids) || !bms_is_subset(outerrel->lateral_relids, innerrel->relids)))
{
if (nestjoinOK)
consider_parallel_nestloop(root, joinrel, outerrel, innerrel,
@@ -1870,7 +1879,9 @@ consider_parallel_nestloop(PlannerInfo *root,
Path *mpath;
/* Can't join to an inner path that is not parallel-safe */
- if (!innerpath->parallel_safe)
+ /* TODO: recheck parallel safety of params here? */
+ if (!innerpath->parallel_safe &&
+ !(innerpath->parallel_safe_ignoring_params))
continue;
/*
diff --git a/src/backend/optimizer/plan/createplan.c b/src/backend/optimizer/plan/createplan.c
index a5f6d678cc..e84834427b 100644
--- a/src/backend/optimizer/plan/createplan.c
+++ b/src/backend/optimizer/plan/createplan.c
@@ -5273,6 +5273,7 @@ copy_generic_path_info(Plan *dest, Path *src)
dest->plan_width = src->pathtarget->width;
dest->parallel_aware = src->parallel_aware;
dest->parallel_safe = src->parallel_safe;
+ dest->parallel_safe_ignoring_params = src->parallel_safe_ignoring_params;
}
/*
@@ -5290,6 +5291,7 @@ copy_plan_costsize(Plan *dest, Plan *src)
dest->parallel_aware = false;
/* Assume the inserted node is parallel-safe, if child plan is. */
dest->parallel_safe = src->parallel_safe;
+ dest->parallel_safe_ignoring_params = src->parallel_safe_ignoring_params;
}
/*
diff --git a/src/backend/optimizer/plan/planmain.c b/src/backend/optimizer/plan/planmain.c
index 273ac0acf7..bdbce2b87d 100644
--- a/src/backend/optimizer/plan/planmain.c
+++ b/src/backend/optimizer/plan/planmain.c
@@ -119,7 +119,7 @@ query_planner(PlannerInfo *root,
if (root->glob->parallelModeOK &&
force_parallel_mode != FORCE_PARALLEL_OFF)
final_rel->consider_parallel =
- is_parallel_safe(root, parse->jointree->quals);
+ is_parallel_safe(root, parse->jointree->quals, NULL);
/*
* The only path for it is a trivial Result path. We cheat a
diff --git a/src/backend/optimizer/plan/planner.c b/src/backend/optimizer/plan/planner.c
index 1e42d75465..25ed2b2788 100644
--- a/src/backend/optimizer/plan/planner.c
+++ b/src/backend/optimizer/plan/planner.c
@@ -150,6 +150,7 @@ static RelOptInfo *create_grouping_paths(PlannerInfo *root,
RelOptInfo *input_rel,
PathTarget *target,
bool target_parallel_safe,
+ bool target_parallel_safe_ignoring_params,
grouping_sets_data *gd);
static bool is_degenerate_grouping(PlannerInfo *root);
static void create_degenerate_grouping_paths(PlannerInfo *root,
@@ -157,6 +158,7 @@ static void create_degenerate_grouping_paths(PlannerInfo *root,
RelOptInfo *grouped_rel);
static RelOptInfo *make_grouping_rel(PlannerInfo *root, RelOptInfo *input_rel,
PathTarget *target, bool target_parallel_safe,
+ bool target_parallel_safe_ignoring_params,
Node *havingQual);
static void create_ordinary_grouping_paths(PlannerInfo *root,
RelOptInfo *input_rel,
@@ -237,6 +239,7 @@ static void apply_scanjoin_target_to_paths(PlannerInfo *root,
List *scanjoin_targets,
List *scanjoin_targets_contain_srfs,
bool scanjoin_target_parallel_safe,
+ bool scanjoin_target_parallel_safe_ignoring_params,
bool tlist_same_exprs);
static void create_partitionwise_grouping_paths(PlannerInfo *root,
RelOptInfo *input_rel,
@@ -1241,6 +1244,7 @@ grouping_planner(PlannerInfo *root, double tuple_fraction)
List *final_targets;
List *final_targets_contain_srfs;
bool final_target_parallel_safe;
+ bool final_target_parallel_safe_ignoring_params = false;
RelOptInfo *current_rel;
RelOptInfo *final_rel;
FinalPathExtraData extra;
@@ -1303,7 +1307,7 @@ grouping_planner(PlannerInfo *root, double tuple_fraction)
/* And check whether it's parallel safe */
final_target_parallel_safe =
- is_parallel_safe(root, (Node *) final_target->exprs);
+ is_parallel_safe(root, (Node *) final_target->exprs, &final_target_parallel_safe_ignoring_params);
/* The setop result tlist couldn't contain any SRFs */
Assert(!parse->hasTargetSRFs);
@@ -1337,14 +1341,17 @@ grouping_planner(PlannerInfo *root, double tuple_fraction)
List *sort_input_targets;
List *sort_input_targets_contain_srfs;
bool sort_input_target_parallel_safe;
+ bool sort_input_target_parallel_safe_ignoring_params = false;
PathTarget *grouping_target;
List *grouping_targets;
List *grouping_targets_contain_srfs;
bool grouping_target_parallel_safe;
+ bool grouping_target_parallel_safe_ignoring_params = false;
PathTarget *scanjoin_target;
List *scanjoin_targets;
List *scanjoin_targets_contain_srfs;
bool scanjoin_target_parallel_safe;
+ bool scanjoin_target_parallel_safe_ignoring_params = false;
bool scanjoin_target_same_exprs;
bool have_grouping;
WindowFuncLists *wflists = NULL;
@@ -1457,7 +1464,7 @@ grouping_planner(PlannerInfo *root, double tuple_fraction)
*/
final_target = create_pathtarget(root, root->processed_tlist);
final_target_parallel_safe =
- is_parallel_safe(root, (Node *) final_target->exprs);
+ is_parallel_safe(root, (Node *) final_target->exprs, &final_target_parallel_safe_ignoring_params);
/*
* If ORDER BY was given, consider whether we should use a post-sort
@@ -1470,12 +1477,13 @@ grouping_planner(PlannerInfo *root, double tuple_fraction)
final_target,
&have_postponed_srfs);
sort_input_target_parallel_safe =
- is_parallel_safe(root, (Node *) sort_input_target->exprs);
+ is_parallel_safe(root, (Node *) sort_input_target->exprs, &sort_input_target_parallel_safe_ignoring_params);
}
else
{
sort_input_target = final_target;
sort_input_target_parallel_safe = final_target_parallel_safe;
+ sort_input_target_parallel_safe_ignoring_params = final_target_parallel_safe_ignoring_params;
}
/*
@@ -1489,12 +1497,13 @@ grouping_planner(PlannerInfo *root, double tuple_fraction)
final_target,
activeWindows);
grouping_target_parallel_safe =
- is_parallel_safe(root, (Node *) grouping_target->exprs);
+ is_parallel_safe(root, (Node *) grouping_target->exprs, &grouping_target_parallel_safe_ignoring_params);
}
else
{
grouping_target = sort_input_target;
grouping_target_parallel_safe = sort_input_target_parallel_safe;
+ grouping_target_parallel_safe_ignoring_params = sort_input_target_parallel_safe_ignoring_params;
}
/*
@@ -1508,12 +1517,13 @@ grouping_planner(PlannerInfo *root, double tuple_fraction)
{
scanjoin_target = make_group_input_target(root, final_target);
scanjoin_target_parallel_safe =
- is_parallel_safe(root, (Node *) scanjoin_target->exprs);
+ is_parallel_safe(root, (Node *) scanjoin_target->exprs, &scanjoin_target_parallel_safe_ignoring_params);
}
else
{
scanjoin_target = grouping_target;
scanjoin_target_parallel_safe = grouping_target_parallel_safe;
+ scanjoin_target_parallel_safe_ignoring_params = grouping_target_parallel_safe_ignoring_params;
}
/*
@@ -1565,6 +1575,7 @@ grouping_planner(PlannerInfo *root, double tuple_fraction)
apply_scanjoin_target_to_paths(root, current_rel, scanjoin_targets,
scanjoin_targets_contain_srfs,
scanjoin_target_parallel_safe,
+ scanjoin_target_parallel_safe_ignoring_params,
scanjoin_target_same_exprs);
/*
@@ -1592,6 +1603,7 @@ grouping_planner(PlannerInfo *root, double tuple_fraction)
current_rel,
grouping_target,
grouping_target_parallel_safe,
+ grouping_target_parallel_safe_ignoring_params,
gset_data);
/* Fix things up if grouping_target contains SRFs */
if (parse->hasTargetSRFs)
@@ -1665,10 +1677,25 @@ grouping_planner(PlannerInfo *root, double tuple_fraction)
* not a SELECT, consider_parallel will be false for every relation in the
* query.
*/
- if (current_rel->consider_parallel &&
- is_parallel_safe(root, parse->limitOffset) &&
- is_parallel_safe(root, parse->limitCount))
- final_rel->consider_parallel = true;
+ if (current_rel->consider_parallel || current_rel->consider_parallel_rechecking_params)
+ {
+ bool limit_count_parallel_safe;
+ bool limit_offset_parallel_safe;
+ bool limit_count_parallel_safe_ignoring_params = false;
+ bool limit_offset_parallel_safe_ignoring_params = false;
+
+ limit_count_parallel_safe = is_parallel_safe(root, parse->limitCount, &limit_count_parallel_safe_ignoring_params);
+ limit_offset_parallel_safe = is_parallel_safe(root, parse->limitOffset, &limit_offset_parallel_safe_ignoring_params);
+
+ if (current_rel->consider_parallel &&
+ limit_count_parallel_safe &&
+ limit_offset_parallel_safe)
+ final_rel->consider_parallel = true;
+ if (current_rel->consider_parallel_rechecking_params &&
+ limit_count_parallel_safe_ignoring_params &&
+ limit_offset_parallel_safe_ignoring_params)
+ final_rel->consider_parallel_rechecking_params = true;
+ }
/*
* If the current_rel belongs to a single FDW, so does the final_rel.
@@ -1869,8 +1896,8 @@ grouping_planner(PlannerInfo *root, double tuple_fraction)
* Generate partial paths for final_rel, too, if outer query levels might
* be able to make use of them.
*/
- if (final_rel->consider_parallel && root->query_level > 1 &&
- !limit_needed(parse))
+ if ((final_rel->consider_parallel || final_rel->consider_parallel_rechecking_params) &&
+ root->query_level > 1 && !limit_needed(parse))
{
Assert(!parse->rowMarks && parse->commandType == CMD_SELECT);
foreach(lc, current_rel->partial_pathlist)
@@ -3282,6 +3309,7 @@ create_grouping_paths(PlannerInfo *root,
RelOptInfo *input_rel,
PathTarget *target,
bool target_parallel_safe,
+ bool target_parallel_safe_ignoring_params,
grouping_sets_data *gd)
{
Query *parse = root->parse;
@@ -3297,7 +3325,9 @@ create_grouping_paths(PlannerInfo *root,
* aggregation paths.
*/
grouped_rel = make_grouping_rel(root, input_rel, target,
- target_parallel_safe, parse->havingQual);
+ target_parallel_safe,
+ target_parallel_safe_ignoring_params,
+ parse->havingQual);
/*
* Create either paths for a degenerate grouping or paths for ordinary
@@ -3358,6 +3388,7 @@ create_grouping_paths(PlannerInfo *root,
extra.flags = flags;
extra.target_parallel_safe = target_parallel_safe;
+ extra.target_parallel_safe_ignoring_params = target_parallel_safe_ignoring_params;
extra.havingQual = parse->havingQual;
extra.targetList = parse->targetList;
extra.partial_costs_set = false;
@@ -3393,7 +3424,7 @@ create_grouping_paths(PlannerInfo *root,
static RelOptInfo *
make_grouping_rel(PlannerInfo *root, RelOptInfo *input_rel,
PathTarget *target, bool target_parallel_safe,
- Node *havingQual)
+ bool target_parallel_safe_ignoring_params, Node *havingQual)
{
RelOptInfo *grouped_rel;
@@ -3421,9 +3452,21 @@ make_grouping_rel(PlannerInfo *root, RelOptInfo *input_rel,
* can't be parallel-safe, either. Otherwise, it's parallel-safe if the
* target list and HAVING quals are parallel-safe.
*/
- if (input_rel->consider_parallel && target_parallel_safe &&
- is_parallel_safe(root, (Node *) havingQual))
- grouped_rel->consider_parallel = true;
+ if ((input_rel->consider_parallel || input_rel->consider_parallel_rechecking_params)
+ && (target_parallel_safe || target_parallel_safe_ignoring_params))
+ {
+ bool having_qual_parallel_safe;
+ bool having_qual_parallel_safe_ignoring_params = false;
+
+ having_qual_parallel_safe = is_parallel_safe(root, (Node *) havingQual,
+ &having_qual_parallel_safe_ignoring_params);
+
+ grouped_rel->consider_parallel = input_rel->consider_parallel &&
+ having_qual_parallel_safe && target_parallel_safe;
+ grouped_rel->consider_parallel_rechecking_params =
+ input_rel->consider_parallel_rechecking_params &&
+ having_qual_parallel_safe_ignoring_params && target_parallel_safe_ignoring_params;
+ }
/*
* If the input rel belongs to a single FDW, so does the grouped rel.
@@ -4050,7 +4093,7 @@ create_window_paths(PlannerInfo *root,
* target list and active windows for non-parallel-safe constructs.
*/
if (input_rel->consider_parallel && output_target_parallel_safe &&
- is_parallel_safe(root, (Node *) activeWindows))
+ is_parallel_safe(root, (Node *) activeWindows, NULL))
window_rel->consider_parallel = true;
/*
@@ -5755,6 +5798,7 @@ adjust_paths_for_srfs(PlannerInfo *root, RelOptInfo *rel,
PathTarget *thistarget = lfirst_node(PathTarget, lc1);
bool contains_srfs = (bool) lfirst_int(lc2);
+ /* TODO: How do we know the new target is parallel safe? */
/* If this level doesn't contain SRFs, do regular projection */
if (contains_srfs)
newpath = (Path *) create_set_projection_path(root,
@@ -6071,8 +6115,8 @@ plan_create_index_workers(Oid tableOid, Oid indexOid)
* safe.
*/
if (heap->rd_rel->relpersistence == RELPERSISTENCE_TEMP ||
- !is_parallel_safe(root, (Node *) RelationGetIndexExpressions(index)) ||
- !is_parallel_safe(root, (Node *) RelationGetIndexPredicate(index)))
+ !is_parallel_safe(root, (Node *) RelationGetIndexExpressions(index), NULL) ||
+ !is_parallel_safe(root, (Node *) RelationGetIndexPredicate(index), NULL))
{
parallel_workers = 0;
goto done;
@@ -6535,6 +6579,8 @@ create_partial_grouping_paths(PlannerInfo *root,
grouped_rel->relids);
partially_grouped_rel->consider_parallel =
grouped_rel->consider_parallel;
+ partially_grouped_rel->consider_parallel_rechecking_params =
+ grouped_rel->consider_parallel_rechecking_params;
partially_grouped_rel->reloptkind = grouped_rel->reloptkind;
partially_grouped_rel->serverid = grouped_rel->serverid;
partially_grouped_rel->userid = grouped_rel->userid;
@@ -6998,6 +7044,7 @@ apply_scanjoin_target_to_paths(PlannerInfo *root,
List *scanjoin_targets,
List *scanjoin_targets_contain_srfs,
bool scanjoin_target_parallel_safe,
+ bool scanjoin_target_parallel_safe_ignoring_params,
bool tlist_same_exprs)
{
bool rel_is_partitioned = IS_PARTITIONED_REL(rel);
@@ -7007,6 +7054,11 @@ apply_scanjoin_target_to_paths(PlannerInfo *root,
/* This recurses, so be paranoid. */
check_stack_depth();
+ /*
+ * TOOD: when/how do we want to generate gather paths if
+ * scanjoin_target_parallel_safe_ignoring_params = true
+ */
+
/*
* If the rel is partitioned, we want to drop its existing paths and
* generate new ones. This function would still be correct if we kept the
@@ -7047,6 +7099,64 @@ apply_scanjoin_target_to_paths(PlannerInfo *root,
generate_useful_gather_paths(root, rel, false);
/* Can't use parallel query above this level. */
+
+ /*
+ * There are cases where:
+ * (rel->consider_parallel &&
+ * !scanjoin_target_parallel_safe &&
+ * scanjoin_target_parallel_safe_ignoring_params)
+ * is true at this point. See longer commment below.
+ */
+ if (!(rel->consider_parallel_rechecking_params && scanjoin_target_parallel_safe_ignoring_params))
+ {
+ /*
+ * TODO: if we limit this to this condition, we're pushing off the
+ * checks as to whether or not a given param usage is safe in the
+ * context of a given path (in the context of a given rel?). That
+ * almost certainly means we'd have to add other checks later (maybe
+ * just on lateral/relids and not parallel safety overall), because
+ * at the end of grouping_planner() we copy partial paths to the
+ * final_rel, and while that path may be acceptable in some contexts
+ * it may not be in all contexts.
+ *
+ * OTOH if we're only dependent on PARAM_EXEC params, and we already
+ * know that subpath->param_info == NULL holds (and that seems like
+ * it must since we were going to replace the path target anyway...
+ * though the one caveat is from the original form of this function
+ * we'd only ever actually assert that for paths not partial paths)
+ * then if a param shows up in the target why would it not be parallel
+ * safe.
+ *
+ * Adding to the mystery even with the original form of this function
+ * we still end up with parallel paths where I'd expect this to
+ * disallow them. For example:
+ *
+ * SELECT '' AS six, f1 AS "Correlated Field", f3 AS "Second Field"
+ * FROM SUBSELECT_TBL upper
+ * WHERE f3 IN (
+ * SELECT upper.f1 + f2
+ * FROM SUBSELECT_TBL
+ * WHERE f2 = CAST(f3 AS integer)
+ * );
+ *
+ * ends up with the correlated query underneath parallel plan despite
+ * its target containing a param, and therefore this function marking
+ * the rel as consider_parallel=false and removing the partial paths.
+ *
+ * But the plan as a whole is parallel safe, and so the subplan is also
+ * parallel safe, which means we can incorporate it into a full parallel
+ * plan. In other words, this is a parallel safe, but not parallel aware
+ * subplan (and regular, not parallel, seq scan inside that subplan).
+ * It's not a partial path; it'a a full path that is executed as a subquery.
+ *
+ * Current conclusion: it's fine for subplans, which is the case we're
+ * currently targeting anyway. And it might even be the only case that
+ * matters at all.
+ */
+ /* rel->consider_parallel_rechecking_params = false; */
+ /* rel->partial_pathlist = NIL; */
+ }
+ rel->consider_parallel_rechecking_params = false;
rel->partial_pathlist = NIL;
rel->consider_parallel = false;
}
@@ -7182,6 +7292,7 @@ apply_scanjoin_target_to_paths(PlannerInfo *root,
child_scanjoin_targets,
scanjoin_targets_contain_srfs,
scanjoin_target_parallel_safe,
+ scanjoin_target_parallel_safe_ignoring_params,
tlist_same_exprs);
/* Save non-dummy children for Append paths. */
@@ -7199,6 +7310,11 @@ apply_scanjoin_target_to_paths(PlannerInfo *root,
* avoid creating multiple Gather nodes within the same plan. We must do
* this after all paths have been generated and before set_cheapest, since
* one of the generated paths may turn out to be the cheapest one.
+ *
+ * TODO: This is the same problem as earlier in this function: when allowing
+ * "parallel safe ignoring params" paths here we don't actually know we are
+ * safe in any possible context just possibly safe in the context of the
+ * right rel.
*/
if (rel->consider_parallel && !IS_OTHER_REL(rel))
generate_useful_gather_paths(root, rel, false);
@@ -7306,6 +7422,7 @@ create_partitionwise_grouping_paths(PlannerInfo *root,
child_grouped_rel = make_grouping_rel(root, child_input_rel,
child_target,
extra->target_parallel_safe,
+ extra->target_parallel_safe_ignoring_params,
child_extra.havingQual);
/* Create grouping paths for this child relation. */
diff --git a/src/backend/optimizer/plan/subselect.c b/src/backend/optimizer/plan/subselect.c
index c9f7a09d10..393db3b42d 100644
--- a/src/backend/optimizer/plan/subselect.c
+++ b/src/backend/optimizer/plan/subselect.c
@@ -342,6 +342,7 @@ build_subplan(PlannerInfo *root, Plan *plan, PlannerInfo *subroot,
splan->useHashTable = false;
splan->unknownEqFalse = unknownEqFalse;
splan->parallel_safe = plan->parallel_safe;
+ splan->parallel_safe_ignoring_params = plan->parallel_safe_ignoring_params;
splan->setParam = NIL;
splan->parParam = NIL;
splan->args = NIL;
@@ -1937,6 +1938,7 @@ process_sublinks_mutator(Node *node, process_sublinks_context *context)
{
SubLink *sublink = (SubLink *) node;
Node *testexpr;
+ Node *result;
/*
* First, recursively process the lefthand-side expressions, if any.
@@ -1948,12 +1950,29 @@ process_sublinks_mutator(Node *node, process_sublinks_context *context)
/*
* Now build the SubPlan node and make the expr to return.
*/
- return make_subplan(context->root,
+ result = make_subplan(context->root,
(Query *) sublink->subselect,
sublink->subLinkType,
sublink->subLinkId,
testexpr,
context->isTopQual);
+
+ /*
+ * If planning determined that a subpath was parallel safe as long
+ * as required params are provided by each individual worker then we
+ * can mark the resulting subplan actually parallel safe since we now
+ * know for certain how that path will be used.
+ */
+ if (IsA(result, SubPlan) && !((SubPlan*)result)->parallel_safe
+ && ((SubPlan*)result)->parallel_safe_ignoring_params
+ && enable_parallel_params_recheck)
+ {
+ Plan *subplan = planner_subplan_get_plan(context->root, (SubPlan*)result);
+ ((SubPlan*)result)->parallel_safe = is_parallel_safe(context->root, testexpr, NULL);
+ subplan->parallel_safe = ((SubPlan*)result)->parallel_safe;
+ }
+
+ return result;
}
/*
diff --git a/src/backend/optimizer/prep/prepunion.c b/src/backend/optimizer/prep/prepunion.c
index e9256a2d4d..16cb35c914 100644
--- a/src/backend/optimizer/prep/prepunion.c
+++ b/src/backend/optimizer/prep/prepunion.c
@@ -409,6 +409,7 @@ recurse_set_operations(Node *setOp, PlannerInfo *root,
Assert(subpath->param_info == NULL);
/* avoid apply_projection_to_path, in case of multiple refs */
+ /* TODO: how to we know the target is parallel safe? */
path = (Path *) create_projection_path(root, subpath->parent,
subpath, target);
lfirst(lc) = path;
diff --git a/src/backend/optimizer/util/clauses.c b/src/backend/optimizer/util/clauses.c
index 3412d31117..e2cf335f4a 100644
--- a/src/backend/optimizer/util/clauses.c
+++ b/src/backend/optimizer/util/clauses.c
@@ -55,6 +55,15 @@
#include "utils/syscache.h"
#include "utils/typcache.h"
+bool enable_parallel_params_recheck = true;
+
+typedef struct
+{
+ PlannerInfo *root;
+ AggSplit aggsplit;
+ AggClauseCosts *costs;
+} get_agg_clause_costs_context;
+
typedef struct
{
ParamListInfo boundParams;
@@ -88,6 +97,8 @@ typedef struct
{
char max_hazard; /* worst proparallel hazard found so far */
char max_interesting; /* worst proparallel hazard of interest */
+ char max_hazard_ignoring_params;
+ bool check_params_independently;
List *safe_param_ids; /* PARAM_EXEC Param IDs to treat as safe */
} max_parallel_hazard_context;
@@ -624,19 +635,27 @@ max_parallel_hazard(Query *parse)
context.max_hazard = PROPARALLEL_SAFE;
context.max_interesting = PROPARALLEL_UNSAFE;
context.safe_param_ids = NIL;
+ context.check_params_independently = false;
(void) max_parallel_hazard_walker((Node *) parse, &context);
return context.max_hazard;
}
/*
* is_parallel_safe
- * Detect whether the given expr contains only parallel-safe functions
+ * Detect whether the given expr contains only parallel safe funcions
+ * XXX: It does more than functions?
+ *
+ * If provided, safe_ignoring_params will be set the result of running the same
+ * parallel safety checks with the exception that params will be allowed. This
+ * value is useful since params are not inherently parallel unsafe, but rather
+ * their usage context (whether or not the worker is able to provide the value)
+ * determines parallel safety.
*
* root->glob->maxParallelHazard must previously have been set to the
- * result of max_parallel_hazard() on the whole query.
+ * result of max_parallel_hazard() on the whole query
*/
bool
-is_parallel_safe(PlannerInfo *root, Node *node)
+is_parallel_safe(PlannerInfo *root, Node *node, bool *safe_ignoring_params)
{
max_parallel_hazard_context context;
PlannerInfo *proot;
@@ -653,8 +672,10 @@ is_parallel_safe(PlannerInfo *root, Node *node)
return true;
/* Else use max_parallel_hazard's search logic, but stop on RESTRICTED */
context.max_hazard = PROPARALLEL_SAFE;
+ context.max_hazard_ignoring_params = PROPARALLEL_SAFE;
context.max_interesting = PROPARALLEL_RESTRICTED;
context.safe_param_ids = NIL;
+ context.check_params_independently = safe_ignoring_params != NULL;
/*
* The params that refer to the same or parent query level are considered
@@ -672,12 +693,17 @@ is_parallel_safe(PlannerInfo *root, Node *node)
}
}
- return !max_parallel_hazard_walker(node, &context);
+ (void) max_parallel_hazard_walker(node, &context);
+
+ if (safe_ignoring_params)
+ *safe_ignoring_params = context.max_hazard_ignoring_params == PROPARALLEL_SAFE;
+
+ return context.max_hazard == PROPARALLEL_SAFE;
}
/* core logic for all parallel-hazard checks */
static bool
-max_parallel_hazard_test(char proparallel, max_parallel_hazard_context *context)
+max_parallel_hazard_test(char proparallel, max_parallel_hazard_context *context, bool from_param)
{
switch (proparallel)
{
@@ -688,12 +714,16 @@ max_parallel_hazard_test(char proparallel, max_parallel_hazard_context *context)
/* increase max_hazard to RESTRICTED */
Assert(context->max_hazard != PROPARALLEL_UNSAFE);
context->max_hazard = proparallel;
+ if (!from_param)
+ context->max_hazard_ignoring_params = proparallel;
/* done if we are not expecting any unsafe functions */
if (context->max_interesting == proparallel)
return true;
break;
case PROPARALLEL_UNSAFE:
context->max_hazard = proparallel;
+ if (!from_param)
+ context->max_hazard_ignoring_params = proparallel;
/* we're always done at the first unsafe construct */
return true;
default:
@@ -708,7 +738,41 @@ static bool
max_parallel_hazard_checker(Oid func_id, void *context)
{
return max_parallel_hazard_test(func_parallel(func_id),
- (max_parallel_hazard_context *) context);
+ (max_parallel_hazard_context *) context, false);
+}
+
+static bool
+max_parallel_hazard_walker_can_short_circuit(max_parallel_hazard_context *context)
+{
+ if (!context->check_params_independently)
+ return true;
+
+ switch (context->max_hazard)
+ {
+ case PROPARALLEL_SAFE:
+ /* nothing to see here, move along */
+ break;
+ case PROPARALLEL_RESTRICTED:
+ if (context->max_interesting == PROPARALLEL_RESTRICTED)
+ return context->max_hazard_ignoring_params != PROPARALLEL_SAFE;
+
+ /*
+ * We haven't even met our max interesting yet, so
+ * we certainly can't short-circuit.
+ */
+ break;
+ case PROPARALLEL_UNSAFE:
+ if (context->max_interesting == PROPARALLEL_RESTRICTED)
+ return context->max_hazard_ignoring_params != PROPARALLEL_SAFE;
+ else if (context->max_interesting == PROPARALLEL_UNSAFE)
+ return context->max_hazard_ignoring_params == PROPARALLEL_UNSAFE;
+
+ break;
+ default:
+ elog(ERROR, "unrecognized proparallel value \"%c\"", context->max_hazard);
+ break;
+ }
+ return false;
}
static bool
@@ -720,7 +784,7 @@ max_parallel_hazard_walker(Node *node, max_parallel_hazard_context *context)
/* Check for hazardous functions in node itself */
if (check_functions_in_node(node, max_parallel_hazard_checker,
context))
- return true;
+ return max_parallel_hazard_walker_can_short_circuit(context);
/*
* It should be OK to treat MinMaxExpr as parallel-safe, since btree
@@ -735,14 +799,14 @@ max_parallel_hazard_walker(Node *node, max_parallel_hazard_context *context)
*/
if (IsA(node, CoerceToDomain))
{
- if (max_parallel_hazard_test(PROPARALLEL_RESTRICTED, context))
- return true;
+ if (max_parallel_hazard_test(PROPARALLEL_RESTRICTED, context, false))
+ return max_parallel_hazard_walker_can_short_circuit(context);
}
else if (IsA(node, NextValueExpr))
{
- if (max_parallel_hazard_test(PROPARALLEL_UNSAFE, context))
- return true;
+ if (max_parallel_hazard_test(PROPARALLEL_UNSAFE, context, false))
+ return max_parallel_hazard_walker_can_short_circuit(context);
}
/*
@@ -755,8 +819,8 @@ max_parallel_hazard_walker(Node *node, max_parallel_hazard_context *context)
*/
else if (IsA(node, WindowFunc))
{
- if (max_parallel_hazard_test(PROPARALLEL_RESTRICTED, context))
- return true;
+ if (max_parallel_hazard_test(PROPARALLEL_RESTRICTED, context, false))
+ return max_parallel_hazard_walker_can_short_circuit(context);
}
/*
@@ -775,8 +839,8 @@ max_parallel_hazard_walker(Node *node, max_parallel_hazard_context *context)
*/
else if (IsA(node, SubLink))
{
- if (max_parallel_hazard_test(PROPARALLEL_RESTRICTED, context))
- return true;
+ if (max_parallel_hazard_test(PROPARALLEL_RESTRICTED, context, false))
+ return max_parallel_hazard_walker_can_short_circuit(context);
}
/*
@@ -791,18 +855,23 @@ max_parallel_hazard_walker(Node *node, max_parallel_hazard_context *context)
List *save_safe_param_ids;
if (!subplan->parallel_safe &&
- max_parallel_hazard_test(PROPARALLEL_RESTRICTED, context))
+ (!enable_parallel_params_recheck || !subplan->parallel_safe_ignoring_params) &&
+ max_parallel_hazard_test(PROPARALLEL_RESTRICTED, context, false) &&
+ max_parallel_hazard_walker_can_short_circuit(context))
return true;
save_safe_param_ids = context->safe_param_ids;
context->safe_param_ids = list_concat_copy(context->safe_param_ids,
subplan->paramIds);
- if (max_parallel_hazard_walker(subplan->testexpr, context))
- return true; /* no need to restore safe_param_ids */
+ if (max_parallel_hazard_walker(subplan->testexpr, context) &&
+ max_parallel_hazard_walker_can_short_circuit(context))
+ /* no need to restore safe_param_ids */
+ return true;
+
list_free(context->safe_param_ids);
context->safe_param_ids = save_safe_param_ids;
/* we must also check args, but no special Param treatment there */
if (max_parallel_hazard_walker((Node *) subplan->args, context))
- return true;
+ return max_parallel_hazard_walker_can_short_circuit(context);
/* don't want to recurse normally, so we're done */
return false;
}
@@ -824,8 +893,8 @@ max_parallel_hazard_walker(Node *node, max_parallel_hazard_context *context)
if (param->paramkind != PARAM_EXEC ||
!list_member_int(context->safe_param_ids, param->paramid))
{
- if (max_parallel_hazard_test(PROPARALLEL_RESTRICTED, context))
- return true;
+ if (max_parallel_hazard_test(PROPARALLEL_RESTRICTED, context, true))
+ return max_parallel_hazard_walker_can_short_circuit(context);
}
return false; /* nothing to recurse to */
}
@@ -843,7 +912,7 @@ max_parallel_hazard_walker(Node *node, max_parallel_hazard_context *context)
if (query->rowMarks != NULL)
{
context->max_hazard = PROPARALLEL_UNSAFE;
- return true;
+ return max_parallel_hazard_walker_can_short_circuit(context);
}
/* Recurse into subselects */
diff --git a/src/backend/optimizer/util/pathnode.c b/src/backend/optimizer/util/pathnode.c
index a53850b370..21be3824c1 100644
--- a/src/backend/optimizer/util/pathnode.c
+++ b/src/backend/optimizer/util/pathnode.c
@@ -756,10 +756,10 @@ add_partial_path(RelOptInfo *parent_rel, Path *new_path)
CHECK_FOR_INTERRUPTS();
/* Path to be added must be parallel safe. */
- Assert(new_path->parallel_safe);
+ Assert(new_path->parallel_safe || new_path->parallel_safe_ignoring_params);
/* Relation should be OK for parallelism, too. */
- Assert(parent_rel->consider_parallel);
+ Assert(parent_rel->consider_parallel || parent_rel->consider_parallel_rechecking_params);
/*
* As in add_path, throw out any paths which are dominated by the new
@@ -938,6 +938,7 @@ create_seqscan_path(PlannerInfo *root, RelOptInfo *rel,
required_outer);
pathnode->parallel_aware = parallel_workers > 0 ? true : false;
pathnode->parallel_safe = rel->consider_parallel;
+ pathnode->parallel_safe_ignoring_params = rel->consider_parallel_rechecking_params;
pathnode->parallel_workers = parallel_workers;
pathnode->pathkeys = NIL; /* seqscan has unordered result */
@@ -1016,6 +1017,7 @@ create_index_path(PlannerInfo *root,
required_outer);
pathnode->path.parallel_aware = false;
pathnode->path.parallel_safe = rel->consider_parallel;
+ pathnode->path.parallel_safe_ignoring_params = rel->consider_parallel_rechecking_params;
pathnode->path.parallel_workers = 0;
pathnode->path.pathkeys = pathkeys;
@@ -1865,7 +1867,7 @@ create_gather_merge_path(PlannerInfo *root, RelOptInfo *rel, Path *subpath,
Cost input_startup_cost = 0;
Cost input_total_cost = 0;
- Assert(subpath->parallel_safe);
+ Assert(subpath->parallel_safe || subpath->parallel_safe_ignoring_params);
Assert(pathkeys);
pathnode->path.pathtype = T_GatherMerge;
@@ -1953,7 +1955,7 @@ create_gather_path(PlannerInfo *root, RelOptInfo *rel, Path *subpath,
{
GatherPath *pathnode = makeNode(GatherPath);
- Assert(subpath->parallel_safe);
+ Assert(subpath->parallel_safe || subpath->parallel_safe_ignoring_params);
pathnode->path.pathtype = T_Gather;
pathnode->path.parent = rel;
@@ -2000,6 +2002,8 @@ create_subqueryscan_path(PlannerInfo *root, RelOptInfo *rel, Path *subpath,
pathnode->path.parallel_aware = false;
pathnode->path.parallel_safe = rel->consider_parallel &&
subpath->parallel_safe;
+ pathnode->path.parallel_safe_ignoring_params = rel->consider_parallel_rechecking_params &&
+ subpath->parallel_safe_ignoring_params;
pathnode->path.parallel_workers = subpath->parallel_workers;
pathnode->path.pathkeys = pathkeys;
pathnode->subpath = subpath;
@@ -2417,6 +2421,8 @@ create_nestloop_path(PlannerInfo *root,
NestPath *pathnode = makeNode(NestPath);
Relids inner_req_outer = PATH_REQ_OUTER(inner_path);
+ /* TODO: Assert lateral relids subset safety? */
+
/*
* If the inner path is parameterized by the outer, we must drop any
* restrict_clauses that are due to be moved into the inner path. We have
@@ -2457,6 +2463,8 @@ create_nestloop_path(PlannerInfo *root,
pathnode->jpath.path.parallel_aware = false;
pathnode->jpath.path.parallel_safe = joinrel->consider_parallel &&
outer_path->parallel_safe && inner_path->parallel_safe;
+ pathnode->jpath.path.parallel_safe_ignoring_params = joinrel->consider_parallel_rechecking_params &&
+ outer_path->parallel_safe_ignoring_params && inner_path->parallel_safe_ignoring_params;
/* This is a foolish way to estimate parallel_workers, but for now... */
pathnode->jpath.path.parallel_workers = outer_path->parallel_workers;
pathnode->jpath.path.pathkeys = pathkeys;
@@ -2630,6 +2638,8 @@ create_projection_path(PlannerInfo *root,
{
ProjectionPath *pathnode = makeNode(ProjectionPath);
PathTarget *oldtarget;
+ bool target_parallel_safe;
+ bool target_parallel_safe_ignoring_params = false;
/*
* We mustn't put a ProjectionPath directly above another; it's useless
@@ -2653,9 +2663,12 @@ create_projection_path(PlannerInfo *root,
/* For now, assume we are above any joins, so no parameterization */
pathnode->path.param_info = NULL;
pathnode->path.parallel_aware = false;
+ target_parallel_safe = is_parallel_safe(root, (Node *) target->exprs,
+ &target_parallel_safe_ignoring_params);
pathnode->path.parallel_safe = rel->consider_parallel &&
- subpath->parallel_safe &&
- is_parallel_safe(root, (Node *) target->exprs);
+ subpath->parallel_safe && target_parallel_safe;
+ pathnode->path.parallel_safe_ignoring_params = rel->consider_parallel_rechecking_params &&
+ subpath->parallel_safe_ignoring_params && target_parallel_safe_ignoring_params;
pathnode->path.parallel_workers = subpath->parallel_workers;
/* Projection does not change the sort order */
pathnode->path.pathkeys = subpath->pathkeys;
@@ -2763,7 +2776,7 @@ apply_projection_to_path(PlannerInfo *root,
* parallel-safe in the target expressions, then we can't.
*/
if ((IsA(path, GatherPath) || IsA(path, GatherMergePath)) &&
- is_parallel_safe(root, (Node *) target->exprs))
+ is_parallel_safe(root, (Node *) target->exprs, NULL))
{
/*
* We always use create_projection_path here, even if the subpath is
@@ -2797,7 +2810,7 @@ apply_projection_to_path(PlannerInfo *root,
}
}
else if (path->parallel_safe &&
- !is_parallel_safe(root, (Node *) target->exprs))
+ !is_parallel_safe(root, (Node *) target->exprs, NULL))
{
/*
* We're inserting a parallel-restricted target list into a path
@@ -2805,6 +2818,7 @@ apply_projection_to_path(PlannerInfo *root,
* safe.
*/
path->parallel_safe = false;
+ path->parallel_safe_ignoring_params = false; /* TODO */
}
return path;
@@ -2837,7 +2851,7 @@ create_set_projection_path(PlannerInfo *root,
pathnode->path.parallel_aware = false;
pathnode->path.parallel_safe = rel->consider_parallel &&
subpath->parallel_safe &&
- is_parallel_safe(root, (Node *) target->exprs);
+ is_parallel_safe(root, (Node *) target->exprs, NULL);
pathnode->path.parallel_workers = subpath->parallel_workers;
/* Projection does not change the sort order XXX? */
pathnode->path.pathkeys = subpath->pathkeys;
@@ -3114,6 +3128,8 @@ create_agg_path(PlannerInfo *root,
pathnode->path.parallel_aware = false;
pathnode->path.parallel_safe = rel->consider_parallel &&
subpath->parallel_safe;
+ pathnode->path.parallel_safe_ignoring_params = rel->consider_parallel_rechecking_params &&
+ subpath->parallel_safe_ignoring_params;
pathnode->path.parallel_workers = subpath->parallel_workers;
if (aggstrategy == AGG_SORTED)
pathnode->path.pathkeys = subpath->pathkeys; /* preserves order */
@@ -3735,6 +3751,8 @@ create_limit_path(PlannerInfo *root, RelOptInfo *rel,
pathnode->path.parallel_aware = false;
pathnode->path.parallel_safe = rel->consider_parallel &&
subpath->parallel_safe;
+ pathnode->path.parallel_safe_ignoring_params = rel->consider_parallel_rechecking_params &&
+ subpath->parallel_safe_ignoring_params;
pathnode->path.parallel_workers = subpath->parallel_workers;
pathnode->path.rows = subpath->rows;
pathnode->path.startup_cost = subpath->startup_cost;
diff --git a/src/backend/optimizer/util/relnode.c b/src/backend/optimizer/util/relnode.c
index 47769cea45..9d908d0fea 100644
--- a/src/backend/optimizer/util/relnode.c
+++ b/src/backend/optimizer/util/relnode.c
@@ -213,6 +213,7 @@ build_simple_rel(PlannerInfo *root, int relid, RelOptInfo *parent)
rel->consider_startup = (root->tuple_fraction > 0);
rel->consider_param_startup = false; /* might get changed later */
rel->consider_parallel = false; /* might get changed later */
+ rel->consider_parallel_rechecking_params = false; /* might get changed later */
rel->reltarget = create_empty_pathtarget();
rel->pathlist = NIL;
rel->ppilist = NIL;
@@ -617,6 +618,7 @@ build_join_rel(PlannerInfo *root,
joinrel->consider_startup = (root->tuple_fraction > 0);
joinrel->consider_param_startup = false;
joinrel->consider_parallel = false;
+ joinrel->consider_parallel_rechecking_params = false;
joinrel->reltarget = create_empty_pathtarget();
joinrel->pathlist = NIL;
joinrel->ppilist = NIL;
@@ -743,10 +745,27 @@ build_join_rel(PlannerInfo *root,
* take; therefore, we should make the same decision here however we get
* here.
*/
- if (inner_rel->consider_parallel && outer_rel->consider_parallel &&
- is_parallel_safe(root, (Node *) restrictlist) &&
- is_parallel_safe(root, (Node *) joinrel->reltarget->exprs))
- joinrel->consider_parallel = true;
+ if ((inner_rel->consider_parallel || inner_rel->consider_parallel_rechecking_params)
+ && (outer_rel->consider_parallel || outer_rel->consider_parallel_rechecking_params))
+ {
+ bool restrictlist_parallel_safe;
+ bool restrictlist_parallel_safe_ignoring_params = false;
+ bool target_parallel_safe;
+ bool target_parallel_safe_ignoring_params = false;
+
+ restrictlist_parallel_safe = is_parallel_safe(root, (Node *) restrictlist, &restrictlist_parallel_safe_ignoring_params);
+ target_parallel_safe = is_parallel_safe(root, (Node *) joinrel->reltarget->exprs, &target_parallel_safe_ignoring_params);
+
+ if (inner_rel->consider_parallel && outer_rel->consider_parallel
+ && restrictlist_parallel_safe && target_parallel_safe)
+ joinrel->consider_parallel = true;
+
+ if (inner_rel->consider_parallel_rechecking_params
+ && outer_rel->consider_parallel_rechecking_params
+ && restrictlist_parallel_safe_ignoring_params
+ && target_parallel_safe_ignoring_params)
+ joinrel->consider_parallel_rechecking_params = true;
+ }
/* Add the joinrel to the PlannerInfo. */
add_join_rel(root, joinrel);
@@ -805,6 +824,7 @@ build_child_join_rel(PlannerInfo *root, RelOptInfo *outer_rel,
joinrel->consider_startup = (root->tuple_fraction > 0);
joinrel->consider_param_startup = false;
joinrel->consider_parallel = false;
+ joinrel->consider_parallel_rechecking_params = false;
joinrel->reltarget = create_empty_pathtarget();
joinrel->pathlist = NIL;
joinrel->ppilist = NIL;
@@ -892,6 +912,7 @@ build_child_join_rel(PlannerInfo *root, RelOptInfo *outer_rel,
/* Child joinrel is parallel safe if parent is parallel safe. */
joinrel->consider_parallel = parent_joinrel->consider_parallel;
+ joinrel->consider_parallel_rechecking_params = parent_joinrel->consider_parallel_rechecking_params;
/* Set estimates of the child-joinrel's size. */
set_joinrel_size_estimates(root, joinrel, outer_rel, inner_rel,
@@ -1236,6 +1257,7 @@ fetch_upper_rel(PlannerInfo *root, UpperRelationKind kind, Relids relids)
upperrel->consider_startup = (root->tuple_fraction > 0);
upperrel->consider_param_startup = false;
upperrel->consider_parallel = false; /* might get changed later */
+ upperrel->consider_parallel_rechecking_params = false; /* might get changed later */
upperrel->reltarget = create_empty_pathtarget();
upperrel->pathlist = NIL;
upperrel->cheapest_startup_path = NULL;
diff --git a/src/backend/utils/misc/guc.c b/src/backend/utils/misc/guc.c
index 467b0fd6fe..034510b611 100644
--- a/src/backend/utils/misc/guc.c
+++ b/src/backend/utils/misc/guc.c
@@ -57,6 +57,7 @@
#include "libpq/libpq.h"
#include "libpq/pqformat.h"
#include "miscadmin.h"
+#include "optimizer/clauses.h"
#include "optimizer/cost.h"
#include "optimizer/geqo.h"
#include "optimizer/optimizer.h"
@@ -968,6 +969,16 @@ static const unit_conversion time_unit_conversion_table[] =
static struct config_bool ConfigureNamesBool[] =
{
+ {
+ {"enable_parallel_params_recheck", PGC_USERSET, QUERY_TUNING_METHOD,
+ gettext_noop("Enables the planner's rechecking of parallel safety in the presence of PARAM_EXEC params (for correlated subqueries)."),
+ NULL,
+ GUC_EXPLAIN
+ },
+ &enable_parallel_params_recheck,
+ true,
+ NULL, NULL, NULL
+ },
{
{"enable_seqscan", PGC_USERSET, QUERY_TUNING_METHOD,
gettext_noop("Enables the planner's use of sequential-scan plans."),
diff --git a/src/include/nodes/pathnodes.h b/src/include/nodes/pathnodes.h
index 1abe233db2..f2c3d229b0 100644
--- a/src/include/nodes/pathnodes.h
+++ b/src/include/nodes/pathnodes.h
@@ -683,6 +683,7 @@ typedef struct RelOptInfo
bool consider_startup; /* keep cheap-startup-cost paths? */
bool consider_param_startup; /* ditto, for parameterized paths? */
bool consider_parallel; /* consider parallel paths? */
+ bool consider_parallel_rechecking_params; /* consider parallel paths? */
/* default result targetlist for Paths scanning this relation */
struct PathTarget *reltarget; /* list of Vars/Exprs, cost, width */
@@ -1182,6 +1183,7 @@ typedef struct Path
bool parallel_aware; /* engage parallel-aware logic? */
bool parallel_safe; /* OK to use as part of parallel plan? */
+ bool parallel_safe_ignoring_params; /* OK to use as part of parallel plan if worker context provides params? */
int parallel_workers; /* desired # of workers; 0 = not parallel */
/* estimated size/costs for path (see costsize.c for more info) */
@@ -2471,7 +2473,7 @@ typedef struct MinMaxAggInfo
* for conflicting purposes.
*
* In addition, PARAM_EXEC slots are assigned for Params representing outputs
- * from subplans (values that are setParam items for those subplans). These
+ * from subplans (values that are setParam items for those subplans). [TODO: is this true, or only for init plans?] These
* IDs need not be tracked via PlannerParamItems, since we do not need any
* duplicate-elimination nor later processing of the represented expressions.
* Instead, we just record the assignment of the slot number by appending to
@@ -2590,6 +2592,7 @@ typedef struct
/* Data which may differ across partitions. */
bool target_parallel_safe;
+ bool target_parallel_safe_ignoring_params;
Node *havingQual;
List *targetList;
PartitionwiseAggregateType patype;
diff --git a/src/include/nodes/plannodes.h b/src/include/nodes/plannodes.h
index ec9a8b0c81..67805f2cfa 100644
--- a/src/include/nodes/plannodes.h
+++ b/src/include/nodes/plannodes.h
@@ -128,6 +128,7 @@ typedef struct Plan
*/
bool parallel_aware; /* engage parallel-aware logic? */
bool parallel_safe; /* OK to use as part of parallel plan? */
+ bool parallel_safe_ignoring_params; /* OK to use as part of parallel plan if worker context provides params? */
/*
* information needed for asynchronous execution
diff --git a/src/include/nodes/primnodes.h b/src/include/nodes/primnodes.h
index c04282f91f..df1e2496c7 100644
--- a/src/include/nodes/primnodes.h
+++ b/src/include/nodes/primnodes.h
@@ -764,6 +764,7 @@ typedef struct SubPlan
* spec result is UNKNOWN; this allows much
* simpler handling of null values */
bool parallel_safe; /* is the subplan parallel-safe? */
+ bool parallel_safe_ignoring_params; /* is the subplan parallel-safe when params are provided by the worker context? */
/* Note: parallel_safe does not consider contents of testexpr or args */
/* Information for passing params into and out of the subselect: */
/* setParam and parParam are lists of integers (param IDs) */
diff --git a/src/include/optimizer/clauses.h b/src/include/optimizer/clauses.h
index 0673887a85..df01be2c61 100644
--- a/src/include/optimizer/clauses.h
+++ b/src/include/optimizer/clauses.h
@@ -16,6 +16,8 @@
#include "nodes/pathnodes.h"
+extern PGDLLIMPORT bool enable_parallel_params_recheck;
+
typedef struct
{
int numWindowFuncs; /* total number of WindowFuncs found */
@@ -33,7 +35,7 @@ extern double expression_returns_set_rows(PlannerInfo *root, Node *clause);
extern bool contain_subplans(Node *clause);
extern char max_parallel_hazard(Query *parse);
-extern bool is_parallel_safe(PlannerInfo *root, Node *node);
+extern bool is_parallel_safe(PlannerInfo *root, Node *node, bool *safe_ignoring_params);
extern bool contain_nonstrict_functions(Node *clause);
extern bool contain_exec_param(Node *clause, List *param_ids);
extern bool contain_leaked_vars(Node *clause);
diff --git a/src/test/regress/expected/incremental_sort.out b/src/test/regress/expected/incremental_sort.out
index 545e301e48..8f9ca05e60 100644
--- a/src/test/regress/expected/incremental_sort.out
+++ b/src/test/regress/expected/incremental_sort.out
@@ -1614,16 +1614,16 @@ from tenk1 t, generate_series(1, 1000);
QUERY PLAN
---------------------------------------------------------------------------------
Unique
- -> Sort
- Sort Key: t.unique1, ((SubPlan 1))
- -> Gather
- Workers Planned: 2
+ -> Gather Merge
+ Workers Planned: 2
+ -> Sort
+ Sort Key: t.unique1, ((SubPlan 1))
-> Nested Loop
-> Parallel Index Only Scan using tenk1_unique1 on tenk1 t
-> Function Scan on generate_series
- SubPlan 1
- -> Index Only Scan using tenk1_unique1 on tenk1
- Index Cond: (unique1 = t.unique1)
+ SubPlan 1
+ -> Index Only Scan using tenk1_unique1 on tenk1
+ Index Cond: (unique1 = t.unique1)
(11 rows)
explain (costs off) select
@@ -1633,16 +1633,16 @@ from tenk1 t, generate_series(1, 1000)
order by 1, 2;
QUERY PLAN
---------------------------------------------------------------------------
- Sort
- Sort Key: t.unique1, ((SubPlan 1))
- -> Gather
- Workers Planned: 2
+ Gather Merge
+ Workers Planned: 2
+ -> Sort
+ Sort Key: t.unique1, ((SubPlan 1))
-> Nested Loop
-> Parallel Index Only Scan using tenk1_unique1 on tenk1 t
-> Function Scan on generate_series
- SubPlan 1
- -> Index Only Scan using tenk1_unique1 on tenk1
- Index Cond: (unique1 = t.unique1)
+ SubPlan 1
+ -> Index Only Scan using tenk1_unique1 on tenk1
+ Index Cond: (unique1 = t.unique1)
(10 rows)
-- Parallel sort but with expression not available until the upper rel.
diff --git a/src/test/regress/expected/select_parallel.out b/src/test/regress/expected/select_parallel.out
index 2303f70d6e..253f117d7a 100644
--- a/src/test/regress/expected/select_parallel.out
+++ b/src/test/regress/expected/select_parallel.out
@@ -311,6 +311,131 @@ select count(*) from tenk1 where (two, four) not in
10000
(1 row)
+-- test parallel plans for queries containing correlated subplans
+-- where the subplan only needs params available from the current
+-- worker's scan.
+explain (costs off, verbose) select
+ (select t.unique1 from tenk1 where tenk1.unique1 = t.unique1)
+ from tenk1 t, generate_series(1, 10);
+ QUERY PLAN
+----------------------------------------------------------------------------
+ Gather
+ Output: ((SubPlan 1))
+ Workers Planned: 4
+ -> Nested Loop
+ Output: (SubPlan 1)
+ -> Parallel Index Only Scan using tenk1_unique1 on public.tenk1 t
+ Output: t.unique1
+ -> Function Scan on pg_catalog.generate_series
+ Output: generate_series.generate_series
+ Function Call: generate_series(1, 10)
+ SubPlan 1
+ -> Index Only Scan using tenk1_unique1 on public.tenk1
+ Output: t.unique1
+ Index Cond: (tenk1.unique1 = t.unique1)
+(14 rows)
+
+explain (costs off, verbose) select
+ (select t.unique1 from tenk1 where tenk1.unique1 = t.unique1)
+ from tenk1 t;
+ QUERY PLAN
+----------------------------------------------------------------------
+ Gather
+ Output: ((SubPlan 1))
+ Workers Planned: 4
+ -> Parallel Index Only Scan using tenk1_unique1 on public.tenk1 t
+ Output: (SubPlan 1)
+ SubPlan 1
+ -> Index Only Scan using tenk1_unique1 on public.tenk1
+ Output: t.unique1
+ Index Cond: (tenk1.unique1 = t.unique1)
+(9 rows)
+
+explain (analyze, costs off, summary off, verbose, timing off) select
+ (select t.unique1 from tenk1 where tenk1.unique1 = t.unique1)
+ from tenk1 t
+ limit 1;
+ QUERY PLAN
+----------------------------------------------------------------------------------------------------
+ Limit (actual rows=1 loops=1)
+ Output: ((SubPlan 1))
+ -> Gather (actual rows=1 loops=1)
+ Output: ((SubPlan 1))
+ Workers Planned: 4
+ Workers Launched: 4
+ -> Parallel Index Only Scan using tenk1_unique1 on public.tenk1 t (actual rows=1 loops=5)
+ Output: (SubPlan 1)
+ Heap Fetches: 0
+ Worker 0: actual rows=1 loops=1
+ Worker 1: actual rows=1 loops=1
+ Worker 2: actual rows=1 loops=1
+ Worker 3: actual rows=1 loops=1
+ SubPlan 1
+ -> Index Only Scan using tenk1_unique1 on public.tenk1 (actual rows=1 loops=5)
+ Output: t.unique1
+ Index Cond: (tenk1.unique1 = t.unique1)
+ Heap Fetches: 0
+ Worker 0: actual rows=1 loops=1
+ Worker 1: actual rows=1 loops=1
+ Worker 2: actual rows=1 loops=1
+ Worker 3: actual rows=1 loops=1
+(22 rows)
+
+explain (costs off, verbose) select t.unique1
+ from tenk1 t
+ where t.unique1 = (select t.unique1 from tenk1 where tenk1.unique1 = t.unique1);
+ QUERY PLAN
+----------------------------------------------------------------------
+ Gather
+ Output: t.unique1
+ Workers Planned: 4
+ -> Parallel Index Only Scan using tenk1_unique1 on public.tenk1 t
+ Output: t.unique1
+ Filter: (t.unique1 = (SubPlan 1))
+ SubPlan 1
+ -> Index Only Scan using tenk1_unique1 on public.tenk1
+ Output: t.unique1
+ Index Cond: (tenk1.unique1 = t.unique1)
+(10 rows)
+
+explain (costs off, verbose) select *
+ from tenk1 t
+ order by (select t.unique1 from tenk1 where tenk1.unique1 = t.unique1);
+ QUERY PLAN
+----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
+ Gather Merge
+ Output: t.unique1, t.unique2, t.two, t.four, t.ten, t.twenty, t.hundred, t.thousand, t.twothousand, t.fivethous, t.tenthous, t.odd, t.even, t.stringu1, t.stringu2, t.string4, ((SubPlan 1))
+ Workers Planned: 4
+ -> Sort
+ Output: t.unique1, t.unique2, t.two, t.four, t.ten, t.twenty, t.hundred, t.thousand, t.twothousand, t.fivethous, t.tenthous, t.odd, t.even, t.stringu1, t.stringu2, t.string4, ((SubPlan 1))
+ Sort Key: ((SubPlan 1))
+ -> Parallel Seq Scan on public.tenk1 t
+ Output: t.unique1, t.unique2, t.two, t.four, t.ten, t.twenty, t.hundred, t.thousand, t.twothousand, t.fivethous, t.tenthous, t.odd, t.even, t.stringu1, t.stringu2, t.string4, (SubPlan 1)
+ SubPlan 1
+ -> Index Only Scan using tenk1_unique1 on public.tenk1
+ Output: t.unique1
+ Index Cond: (tenk1.unique1 = t.unique1)
+(12 rows)
+
+-- test subplan in join/lateral join
+explain (costs off, verbose, timing off) select t.unique1, l.*
+ from tenk1 t
+ join lateral (
+ select (select t.unique1 from tenk1 where tenk1.unique1 = t.unique1 offset 0)
+ ) l on true;
+ QUERY PLAN
+----------------------------------------------------------------------
+ Gather
+ Output: t.unique1, ((SubPlan 1))
+ Workers Planned: 4
+ -> Parallel Index Only Scan using tenk1_unique1 on public.tenk1 t
+ Output: t.unique1, (SubPlan 1)
+ SubPlan 1
+ -> Index Only Scan using tenk1_unique1 on public.tenk1
+ Output: t.unique1
+ Index Cond: (tenk1.unique1 = t.unique1)
+(9 rows)
+
-- this is not parallel-safe due to use of random() within SubLink's testexpr:
explain (costs off)
select * from tenk1 where (unique1 + random())::integer not in
@@ -1192,6 +1317,18 @@ EXECUTE pstmt('1', make_some_array(1,2));
DEALLOCATE pstmt;
-- test interaction between subquery and partial_paths
+-- this plan changes to using a non-parallel index only
+-- scan on tenk1_unique1 (the parallel version of the subquery scan
+-- is cheaper, but only by ~30, and cost comparison treats them as equal
+-- since the costs are so large) because set_rel_consider_parallel
+-- called from make_one_rel sees the subplan as parallel safe now
+-- (in context it now knows the params are actually parallel safe).
+-- Because of that the non-parallel index path is now parallel_safe=true,
+-- therefore it wins the COSTS_EQUAL comparison in add_path.
+-- Perhaps any is_parallel_safe calls made for the purpose of determining
+-- consider_parallel should disable that behavior? It's not clear which is
+-- correct.
+set enable_parallel_params_recheck = off;
CREATE VIEW tenk1_vw_sec WITH (security_barrier) AS SELECT * FROM tenk1;
EXPLAIN (COSTS OFF)
SELECT 1 FROM tenk1_vw_sec
diff --git a/src/test/regress/expected/sysviews.out b/src/test/regress/expected/sysviews.out
index 6e54f3e15e..e4b48fc61d 100644
--- a/src/test/regress/expected/sysviews.out
+++ b/src/test/regress/expected/sysviews.out
@@ -109,13 +109,14 @@ select name, setting from pg_settings where name like 'enable%';
enable_nestloop | on
enable_parallel_append | on
enable_parallel_hash | on
+ enable_parallel_params_recheck | on
enable_partition_pruning | on
enable_partitionwise_aggregate | off
enable_partitionwise_join | off
enable_seqscan | on
enable_sort | on
enable_tidscan | on
-(20 rows)
+(21 rows)
-- Test that the pg_timezone_names and pg_timezone_abbrevs views are
-- more-or-less working. We can't test their contents in any great detail
diff --git a/src/test/regress/sql/select_parallel.sql b/src/test/regress/sql/select_parallel.sql
index 019e17e751..f217d0ec9b 100644
--- a/src/test/regress/sql/select_parallel.sql
+++ b/src/test/regress/sql/select_parallel.sql
@@ -111,6 +111,31 @@ explain (costs off)
(select hundred, thousand from tenk2 where thousand > 100);
select count(*) from tenk1 where (two, four) not in
(select hundred, thousand from tenk2 where thousand > 100);
+-- test parallel plans for queries containing correlated subplans
+-- where the subplan only needs params available from the current
+-- worker's scan.
+explain (costs off, verbose) select
+ (select t.unique1 from tenk1 where tenk1.unique1 = t.unique1)
+ from tenk1 t, generate_series(1, 10);
+explain (costs off, verbose) select
+ (select t.unique1 from tenk1 where tenk1.unique1 = t.unique1)
+ from tenk1 t;
+explain (analyze, costs off, summary off, verbose, timing off) select
+ (select t.unique1 from tenk1 where tenk1.unique1 = t.unique1)
+ from tenk1 t
+ limit 1;
+explain (costs off, verbose) select t.unique1
+ from tenk1 t
+ where t.unique1 = (select t.unique1 from tenk1 where tenk1.unique1 = t.unique1);
+explain (costs off, verbose) select *
+ from tenk1 t
+ order by (select t.unique1 from tenk1 where tenk1.unique1 = t.unique1);
+-- test subplan in join/lateral join
+explain (costs off, verbose, timing off) select t.unique1, l.*
+ from tenk1 t
+ join lateral (
+ select (select t.unique1 from tenk1 where tenk1.unique1 = t.unique1 offset 0)
+ ) l on true;
-- this is not parallel-safe due to use of random() within SubLink's testexpr:
explain (costs off)
select * from tenk1 where (unique1 + random())::integer not in
@@ -456,6 +481,18 @@ EXECUTE pstmt('1', make_some_array(1,2));
DEALLOCATE pstmt;
-- test interaction between subquery and partial_paths
+-- this plan changes to using a non-parallel index only
+-- scan on tenk1_unique1 (the parallel version of the subquery scan
+-- is cheaper, but only by ~30, and cost comparison treats them as equal
+-- since the costs are so large) because set_rel_consider_parallel
+-- called from make_one_rel sees the subplan as parallel safe now
+-- (in context it now knows the params are actually parallel safe).
+-- Because of that the non-parallel index path is now parallel_safe=true,
+-- therefore it wins the COSTS_EQUAL comparison in add_path.
+-- Perhaps any is_parallel_safe calls made for the purpose of determining
+-- consider_parallel should disable that behavior? It's not clear which is
+-- correct.
+set enable_parallel_params_recheck = off;
CREATE VIEW tenk1_vw_sec WITH (security_barrier) AS SELECT * FROM tenk1;
EXPLAIN (COSTS OFF)
SELECT 1 FROM tenk1_vw_sec
--
2.20.1
[application/octet-stream] v2-0003-Other-places-to-consider-for-completeness.patch (5.1K, ../../CAAaqYe8D2Mpp8T6oqcTRtTBOWVaCA6_1542A1BgBB4xthtXhkw@mail.gmail.com/4-v2-0003-Other-places-to-consider-for-completeness.patch)
download | inline diff:
From 4132c2144c71c4dac91a0428e97f6d5d81843f62 Mon Sep 17 00:00:00 2001
From: jcoleman <[email protected]>
Date: Fri, 7 May 2021 15:37:22 +0000
Subject: [PATCH v2 3/3] Other places to consider for completeness
---
src/backend/optimizer/path/allpaths.c | 4 ++++
src/backend/optimizer/plan/planmain.c | 2 +-
src/backend/optimizer/plan/planner.c | 3 +++
src/backend/optimizer/plan/subselect.c | 3 +++
src/backend/optimizer/prep/prepunion.c | 2 ++
5 files changed, 13 insertions(+), 1 deletion(-)
diff --git a/src/backend/optimizer/path/allpaths.c b/src/backend/optimizer/path/allpaths.c
index 5ab6d0e23f..17438d2ea1 100644
--- a/src/backend/optimizer/path/allpaths.c
+++ b/src/backend/optimizer/path/allpaths.c
@@ -1142,6 +1142,8 @@ set_append_rel_size(PlannerInfo *root, RelOptInfo *rel,
*/
if (!childrel->consider_parallel)
rel->consider_parallel = false;
+ if (!childrel->consider_parallel_rechecking_params)
+ rel->consider_parallel_rechecking_params = false;
/*
* Accumulate size information from each live child.
@@ -1263,6 +1265,8 @@ set_append_rel_pathlist(PlannerInfo *root, RelOptInfo *rel,
*/
if (!rel->consider_parallel)
childrel->consider_parallel = false;
+ if (!childrel->consider_parallel_rechecking_params)
+ rel->consider_parallel_rechecking_params = false;
/*
* Compute the child's access paths.
diff --git a/src/backend/optimizer/plan/planmain.c b/src/backend/optimizer/plan/planmain.c
index bdbce2b87d..5135f9ee97 100644
--- a/src/backend/optimizer/plan/planmain.c
+++ b/src/backend/optimizer/plan/planmain.c
@@ -119,7 +119,7 @@ query_planner(PlannerInfo *root,
if (root->glob->parallelModeOK &&
force_parallel_mode != FORCE_PARALLEL_OFF)
final_rel->consider_parallel =
- is_parallel_safe(root, parse->jointree->quals, NULL);
+ is_parallel_safe(root, parse->jointree->quals, &final_rel->consider_parallel_rechecking_params);
/*
* The only path for it is a trivial Result path. We cheat a
diff --git a/src/backend/optimizer/plan/planner.c b/src/backend/optimizer/plan/planner.c
index 25ed2b2788..7cde1da3c3 100644
--- a/src/backend/optimizer/plan/planner.c
+++ b/src/backend/optimizer/plan/planner.c
@@ -4095,6 +4095,7 @@ create_window_paths(PlannerInfo *root,
if (input_rel->consider_parallel && output_target_parallel_safe &&
is_parallel_safe(root, (Node *) activeWindows, NULL))
window_rel->consider_parallel = true;
+ /* consider_parallel_rechecking_params */
/*
* If the input rel belongs to a single FDW, so does the window rel.
@@ -4292,6 +4293,7 @@ create_distinct_paths(PlannerInfo *root, RelOptInfo *input_rel)
* expressions are parallel-safe.
*/
distinct_rel->consider_parallel = input_rel->consider_parallel;
+ distinct_rel->consider_parallel_rechecking_params = input_rel->consider_parallel_rechecking_params;
/*
* If the input rel belongs to a single FDW, so does the distinct_rel.
@@ -4646,6 +4648,7 @@ create_ordered_paths(PlannerInfo *root,
*/
if (input_rel->consider_parallel && target_parallel_safe)
ordered_rel->consider_parallel = true;
+ /* consider_parallel_rechecking_params */
/*
* If the input rel belongs to a single FDW, so does the ordered_rel.
diff --git a/src/backend/optimizer/plan/subselect.c b/src/backend/optimizer/plan/subselect.c
index 393db3b42d..3e1001fa86 100644
--- a/src/backend/optimizer/plan/subselect.c
+++ b/src/backend/optimizer/plan/subselect.c
@@ -1020,6 +1020,7 @@ SS_process_ctes(PlannerInfo *root)
* parallel-safe.
*/
splan->parallel_safe = false;
+ splan->parallel_safe_ignoring_params = false;
splan->setParam = NIL;
splan->parParam = NIL;
splan->args = NIL;
@@ -2176,6 +2177,7 @@ SS_charge_for_initplans(PlannerInfo *root, RelOptInfo *final_rel)
path->startup_cost += initplan_cost;
path->total_cost += initplan_cost;
path->parallel_safe = false;
+ path->parallel_safe_ignoring_params = false;
}
/*
@@ -2184,6 +2186,7 @@ SS_charge_for_initplans(PlannerInfo *root, RelOptInfo *final_rel)
*/
final_rel->partial_pathlist = NIL;
final_rel->consider_parallel = false;
+ final_rel->consider_parallel_rechecking_params = false;
/* We needn't do set_cheapest() here, caller will do it */
}
diff --git a/src/backend/optimizer/prep/prepunion.c b/src/backend/optimizer/prep/prepunion.c
index 16cb35c914..ab92e7d7e4 100644
--- a/src/backend/optimizer/prep/prepunion.c
+++ b/src/backend/optimizer/prep/prepunion.c
@@ -273,6 +273,7 @@ recurse_set_operations(Node *setOp, PlannerInfo *root,
*/
final_rel = fetch_upper_rel(subroot, UPPERREL_FINAL, NULL);
rel->consider_parallel = final_rel->consider_parallel;
+ rel->consider_parallel_rechecking_params = final_rel->consider_parallel_rechecking_params;
/*
* For the moment, we consider only a single Path for the subquery.
@@ -617,6 +618,7 @@ generate_union_paths(SetOperationStmt *op, PlannerInfo *root,
result_rel = fetch_upper_rel(root, UPPERREL_SETOP, relids);
result_rel->reltarget = create_pathtarget(root, tlist);
result_rel->consider_parallel = consider_parallel;
+ /* consider_parallel_rechecking_params */
/*
* Append the child results together.
--
2.20.1
^ permalink raw reply [nested|flat] 35+ messages in thread
* Re: Parallelize correlated subqueries that execute within each worker
@ 2021-09-07 15:06 Zhihong Yu <[email protected]>
parent: James Coleman <[email protected]>
0 siblings, 1 reply; 35+ messages in thread
From: Zhihong Yu @ 2021-09-07 15:06 UTC (permalink / raw)
To: James Coleman <[email protected]>; +Cc: Daniel Gustafsson <[email protected]>; pgsql-hackers; Amit Kapila <[email protected]>
On Tue, Sep 7, 2021 at 6:17 AM James Coleman <[email protected]> wrote:
> On Wed, Sep 1, 2021 at 7:06 AM Daniel Gustafsson <[email protected]> wrote:
> >
> > > On 7 May 2021, at 18:30, James Coleman <[email protected]> wrote:
> >
> > > ..here we are now, and I finally have this patch cleaned up
> > > enough to share.
> >
> > This patch no longer applies to HEAD, can you please submit a rebased
> version?
>
> See attached.
>
> Thanks,
> James
>
Hi,
For v2-0002-Parallel-query-support-for-basic-correlated-subqu.patch :
+ * is when we're going to execute multiple partial parths in parallel
parths -> paths
if (index->amcanparallel &&
- rel->consider_parallel && outer_relids == NULL &&
- scantype != ST_BITMAPSCAN)
+ rel->consider_parallel && outer_relids == NULL &&
+ scantype != ST_BITMAPSCAN)
the change above seems unnecessary since the first line of if condition
doesn't change.
Similar comment for the next hunk.
+ * It's not a partial path; it'a a full path that is executed
as a subquery.
it'a a -> it's a
+ /* rel->consider_parallel_rechecking_params = false; */
+ /* rel->partial_pathlist = NIL; */
The commented code can be taken out.
Cheers
^ permalink raw reply [nested|flat] 35+ messages in thread
* Re: Parallelize correlated subqueries that execute within each worker
@ 2021-09-08 12:47 James Coleman <[email protected]>
parent: Zhihong Yu <[email protected]>
0 siblings, 1 reply; 35+ messages in thread
From: James Coleman @ 2021-09-08 12:47 UTC (permalink / raw)
To: Zhihong Yu <[email protected]>; +Cc: Daniel Gustafsson <[email protected]>; pgsql-hackers; Amit Kapila <[email protected]>
On Tue, Sep 7, 2021 at 11:06 AM Zhihong Yu <[email protected]> wrote:
>
>
>
> On Tue, Sep 7, 2021 at 6:17 AM James Coleman <[email protected]> wrote:
>>
>> On Wed, Sep 1, 2021 at 7:06 AM Daniel Gustafsson <[email protected]> wrote:
>> >
>> > > On 7 May 2021, at 18:30, James Coleman <[email protected]> wrote:
>> >
>> > > ..here we are now, and I finally have this patch cleaned up
>> > > enough to share.
>> >
>> > This patch no longer applies to HEAD, can you please submit a rebased version?
>>
>> See attached.
>>
>> Thanks,
>> James
>
> Hi,
> For v2-0002-Parallel-query-support-for-basic-correlated-subqu.patch :
>
> + * is when we're going to execute multiple partial parths in parallel
>
> parths -> paths
>
> if (index->amcanparallel &&
> - rel->consider_parallel && outer_relids == NULL &&
> - scantype != ST_BITMAPSCAN)
> + rel->consider_parallel && outer_relids == NULL &&
> + scantype != ST_BITMAPSCAN)
>
> the change above seems unnecessary since the first line of if condition doesn't change.
> Similar comment for the next hunk.
>
> + * It's not a partial path; it'a a full path that is executed as a subquery.
>
> it'a a -> it's a
>
> + /* rel->consider_parallel_rechecking_params = false; */
> + /* rel->partial_pathlist = NIL; */
>
> The commented code can be taken out.
Thanks for taking a look at this.
See updated patch series attached.
James Coleman
Attachments:
[application/octet-stream] v3-0001-Allow-parallel-LATERAL-subqueries-with-LIMIT-OFFS.patch (3.5K, ../../CAAaqYe-mts0pTD7B3b0+0g_aUwErEiL=mhGZfj9TEGmza-jt3Q@mail.gmail.com/2-v3-0001-Allow-parallel-LATERAL-subqueries-with-LIMIT-OFFS.patch)
download | inline diff:
From 7ba602847a13fbf7c87aab3651b4304ffba5e9e6 Mon Sep 17 00:00:00 2001
From: jcoleman <[email protected]>
Date: Mon, 30 Nov 2020 11:36:35 -0500
Subject: [PATCH v3 1/3] Allow parallel LATERAL subqueries with LIMIT/OFFSET
The code that determined whether or not a rel should be considered for
parallel query excluded subqueries with LIMIT/OFFSET. That's correct in
the general case: as the comment notes that'd mean we have to guarantee
ordering (and claims it's not worth checking that) for results to be
consistent across workers. However there's a simpler case that hasn't
been considered: LATERAL subqueries with LIMIT/OFFSET don't fall under
the same reasoning since they're executed (when not converted to a JOIN)
per tuple anyway, so consistency of results across workers isn't a
factor.
---
src/backend/optimizer/path/allpaths.c | 4 +++-
src/test/regress/expected/select_parallel.out | 15 +++++++++++++++
src/test/regress/sql/select_parallel.sql | 6 ++++++
3 files changed, 24 insertions(+), 1 deletion(-)
diff --git a/src/backend/optimizer/path/allpaths.c b/src/backend/optimizer/path/allpaths.c
index 296dd75c1b..1363f1bc6c 100644
--- a/src/backend/optimizer/path/allpaths.c
+++ b/src/backend/optimizer/path/allpaths.c
@@ -682,11 +682,13 @@ set_rel_consider_parallel(PlannerInfo *root, RelOptInfo *rel,
* inconsistent results at the top-level. (In some cases, where
* the result is ordered, we could relax this restriction. But it
* doesn't currently seem worth expending extra effort to do so.)
+ * LATERAL is an exception: LIMIT/OFFSET is safe to execute within
+ * workers since the sub-select is executed per tuple
*/
{
Query *subquery = castNode(Query, rte->subquery);
- if (limit_needed(subquery))
+ if (!rte->lateral && limit_needed(subquery))
return;
}
break;
diff --git a/src/test/regress/expected/select_parallel.out b/src/test/regress/expected/select_parallel.out
index 4ea1aa7dfd..2303f70d6e 100644
--- a/src/test/regress/expected/select_parallel.out
+++ b/src/test/regress/expected/select_parallel.out
@@ -1040,6 +1040,21 @@ explain (costs off)
Filter: (stringu1 ~~ '%AAAA'::text)
(11 rows)
+-- ...unless it's LATERAL
+savepoint settings;
+set parallel_tuple_cost=0;
+explain (costs off) select t.unique1 from tenk1 t
+join lateral (select t.unique1 from tenk1 offset 0) l on true;
+ QUERY PLAN
+---------------------------------------------------------------------
+ Gather
+ Workers Planned: 4
+ -> Nested Loop
+ -> Parallel Index Only Scan using tenk1_unique1 on tenk1 t
+ -> Index Only Scan using tenk1_hundred on tenk1
+(5 rows)
+
+rollback to savepoint settings;
-- to increase the parallel query test coverage
SAVEPOINT settings;
SET LOCAL force_parallel_mode = 1;
diff --git a/src/test/regress/sql/select_parallel.sql b/src/test/regress/sql/select_parallel.sql
index f924731248..019e17e751 100644
--- a/src/test/regress/sql/select_parallel.sql
+++ b/src/test/regress/sql/select_parallel.sql
@@ -390,6 +390,12 @@ explain (costs off, verbose)
explain (costs off)
select * from tenk1 a where two in
(select two from tenk1 b where stringu1 like '%AAAA' limit 3);
+-- ...unless it's LATERAL
+savepoint settings;
+set parallel_tuple_cost=0;
+explain (costs off) select t.unique1 from tenk1 t
+join lateral (select t.unique1 from tenk1 offset 0) l on true;
+rollback to savepoint settings;
-- to increase the parallel query test coverage
SAVEPOINT settings;
--
2.20.1
[application/octet-stream] v3-0002-Parallel-query-support-for-basic-correlated-subqu.patch (75.0K, ../../CAAaqYe-mts0pTD7B3b0+0g_aUwErEiL=mhGZfj9TEGmza-jt3Q@mail.gmail.com/3-v3-0002-Parallel-query-support-for-basic-correlated-subqu.patch)
download | inline diff:
From f89bd7f6af26e16e2f625e6ee05dbc390a300b38 Mon Sep 17 00:00:00 2001
From: jcoleman <[email protected]>
Date: Fri, 27 Nov 2020 18:44:30 -0500
Subject: [PATCH v3 2/3] Parallel query support for basic correlated subqueries
Not all Params are inherently parallel-unsafe, but we can't know whether
they're parallel-safe up-front: we need contextual information for a
given path shape. Here we delay the final determination of whether or
not a Param is parallel-safe by initially verifying that it is minimally
parallel-safe for things that are inherent (e.g., no parallel-unsafe
functions or relations involved) and later re-checking that a given
usage is contextually safe (e.g., the Param is for correlation that can
happen entirely within a parallel worker (as opposed to needing to pass
values between workers).
---
doc/src/sgml/parallel.sgml | 3 +-
src/backend/nodes/copyfuncs.c | 2 +
src/backend/nodes/equalfuncs.c | 1 +
src/backend/nodes/outfuncs.c | 3 +
src/backend/nodes/readfuncs.c | 2 +
src/backend/optimizer/path/allpaths.c | 61 +++++--
src/backend/optimizer/path/equivclass.c | 4 +-
src/backend/optimizer/path/indxpath.c | 12 ++
src/backend/optimizer/path/joinpath.c | 21 ++-
src/backend/optimizer/plan/createplan.c | 2 +
src/backend/optimizer/plan/planmain.c | 2 +-
src/backend/optimizer/plan/planner.c | 158 +++++++++++++++---
src/backend/optimizer/plan/subselect.c | 21 ++-
src/backend/optimizer/prep/prepunion.c | 1 +
src/backend/optimizer/util/clauses.c | 113 ++++++++++---
src/backend/optimizer/util/pathnode.c | 36 +++-
src/backend/optimizer/util/relnode.c | 30 +++-
src/backend/utils/misc/guc.c | 11 ++
src/include/nodes/pathnodes.h | 5 +-
src/include/nodes/plannodes.h | 1 +
src/include/nodes/primnodes.h | 1 +
src/include/optimizer/clauses.h | 4 +-
.../regress/expected/incremental_sort.out | 28 ++--
src/test/regress/expected/select_parallel.out | 137 +++++++++++++++
src/test/regress/expected/sysviews.out | 3 +-
src/test/regress/sql/select_parallel.sql | 37 ++++
26 files changed, 603 insertions(+), 96 deletions(-)
diff --git a/doc/src/sgml/parallel.sgml b/doc/src/sgml/parallel.sgml
index 13479d7e5e..2d924dd2ac 100644
--- a/doc/src/sgml/parallel.sgml
+++ b/doc/src/sgml/parallel.sgml
@@ -517,7 +517,8 @@ EXPLAIN SELECT * FROM pgbench_accounts WHERE filler LIKE '%x%';
<listitem>
<para>
- Plan nodes that reference a correlated <literal>SubPlan</literal>.
+ Plan nodes that reference a correlated <literal>SubPlan</literal> where
+ the result is shared between workers.
</para>
</listitem>
</itemizedlist>
diff --git a/src/backend/nodes/copyfuncs.c b/src/backend/nodes/copyfuncs.c
index 38251c2b8e..4042cef2ea 100644
--- a/src/backend/nodes/copyfuncs.c
+++ b/src/backend/nodes/copyfuncs.c
@@ -124,6 +124,7 @@ CopyPlanFields(const Plan *from, Plan *newnode)
COPY_SCALAR_FIELD(parallel_aware);
COPY_SCALAR_FIELD(parallel_safe);
COPY_SCALAR_FIELD(async_capable);
+ COPY_SCALAR_FIELD(parallel_safe_ignoring_params);
COPY_SCALAR_FIELD(plan_node_id);
COPY_NODE_FIELD(targetlist);
COPY_NODE_FIELD(qual);
@@ -1767,6 +1768,7 @@ _copySubPlan(const SubPlan *from)
COPY_SCALAR_FIELD(useHashTable);
COPY_SCALAR_FIELD(unknownEqFalse);
COPY_SCALAR_FIELD(parallel_safe);
+ COPY_SCALAR_FIELD(parallel_safe_ignoring_params);
COPY_NODE_FIELD(setParam);
COPY_NODE_FIELD(parParam);
COPY_NODE_FIELD(args);
diff --git a/src/backend/nodes/equalfuncs.c b/src/backend/nodes/equalfuncs.c
index 8a1762000c..482063c066 100644
--- a/src/backend/nodes/equalfuncs.c
+++ b/src/backend/nodes/equalfuncs.c
@@ -465,6 +465,7 @@ _equalSubPlan(const SubPlan *a, const SubPlan *b)
COMPARE_SCALAR_FIELD(useHashTable);
COMPARE_SCALAR_FIELD(unknownEqFalse);
COMPARE_SCALAR_FIELD(parallel_safe);
+ COMPARE_SCALAR_FIELD(parallel_safe_ignoring_params);
COMPARE_NODE_FIELD(setParam);
COMPARE_NODE_FIELD(parParam);
COMPARE_NODE_FIELD(args);
diff --git a/src/backend/nodes/outfuncs.c b/src/backend/nodes/outfuncs.c
index 87561cbb6f..42dbb05db5 100644
--- a/src/backend/nodes/outfuncs.c
+++ b/src/backend/nodes/outfuncs.c
@@ -334,6 +334,7 @@ _outPlanInfo(StringInfo str, const Plan *node)
WRITE_BOOL_FIELD(parallel_aware);
WRITE_BOOL_FIELD(parallel_safe);
WRITE_BOOL_FIELD(async_capable);
+ WRITE_BOOL_FIELD(parallel_safe_ignoring_params);
WRITE_INT_FIELD(plan_node_id);
WRITE_NODE_FIELD(targetlist);
WRITE_NODE_FIELD(qual);
@@ -1374,6 +1375,7 @@ _outSubPlan(StringInfo str, const SubPlan *node)
WRITE_BOOL_FIELD(useHashTable);
WRITE_BOOL_FIELD(unknownEqFalse);
WRITE_BOOL_FIELD(parallel_safe);
+ WRITE_BOOL_FIELD(parallel_safe_ignoring_params);
WRITE_NODE_FIELD(setParam);
WRITE_NODE_FIELD(parParam);
WRITE_NODE_FIELD(args);
@@ -1772,6 +1774,7 @@ _outPathInfo(StringInfo str, const Path *node)
outBitmapset(str, NULL);
WRITE_BOOL_FIELD(parallel_aware);
WRITE_BOOL_FIELD(parallel_safe);
+ WRITE_BOOL_FIELD(parallel_safe_ignoring_params);
WRITE_INT_FIELD(parallel_workers);
WRITE_FLOAT_FIELD(rows, "%.0f");
WRITE_FLOAT_FIELD(startup_cost, "%.2f");
diff --git a/src/backend/nodes/readfuncs.c b/src/backend/nodes/readfuncs.c
index 0dd1ad7dfc..b6598726bb 100644
--- a/src/backend/nodes/readfuncs.c
+++ b/src/backend/nodes/readfuncs.c
@@ -1621,6 +1621,7 @@ ReadCommonPlan(Plan *local_node)
READ_BOOL_FIELD(parallel_aware);
READ_BOOL_FIELD(parallel_safe);
READ_BOOL_FIELD(async_capable);
+ READ_BOOL_FIELD(parallel_safe_ignoring_params);
READ_INT_FIELD(plan_node_id);
READ_NODE_FIELD(targetlist);
READ_NODE_FIELD(qual);
@@ -2615,6 +2616,7 @@ _readSubPlan(void)
READ_BOOL_FIELD(useHashTable);
READ_BOOL_FIELD(unknownEqFalse);
READ_BOOL_FIELD(parallel_safe);
+ READ_BOOL_FIELD(parallel_safe_ignoring_params);
READ_NODE_FIELD(setParam);
READ_NODE_FIELD(parParam);
READ_NODE_FIELD(args);
diff --git a/src/backend/optimizer/path/allpaths.c b/src/backend/optimizer/path/allpaths.c
index 1363f1bc6c..6eb39e6a06 100644
--- a/src/backend/optimizer/path/allpaths.c
+++ b/src/backend/optimizer/path/allpaths.c
@@ -556,7 +556,8 @@ set_rel_pathlist(PlannerInfo *root, RelOptInfo *rel,
* (see grouping_planner).
*/
if (rel->reloptkind == RELOPT_BASEREL &&
- bms_membership(root->all_baserels) != BMS_SINGLETON)
+ bms_membership(root->all_baserels) != BMS_SINGLETON
+ && (rel->subplan_params == NIL || rte->rtekind != RTE_SUBQUERY))
generate_useful_gather_paths(root, rel, false);
/* Now find the cheapest of the paths for this rel */
@@ -592,6 +593,9 @@ static void
set_rel_consider_parallel(PlannerInfo *root, RelOptInfo *rel,
RangeTblEntry *rte)
{
+ bool parallel_safe;
+ bool parallel_safe_except_in_params;
+
/*
* The flag has previously been initialized to false, so we can just
* return if it becomes clear that we can't safely set it.
@@ -632,7 +636,7 @@ set_rel_consider_parallel(PlannerInfo *root, RelOptInfo *rel,
if (proparallel != PROPARALLEL_SAFE)
return;
- if (!is_parallel_safe(root, (Node *) rte->tablesample->args))
+ if (!is_parallel_safe(root, (Node *) rte->tablesample->args, NULL))
return;
}
@@ -700,7 +704,7 @@ set_rel_consider_parallel(PlannerInfo *root, RelOptInfo *rel,
case RTE_FUNCTION:
/* Check for parallel-restricted functions. */
- if (!is_parallel_safe(root, (Node *) rte->functions))
+ if (!is_parallel_safe(root, (Node *) rte->functions, NULL))
return;
break;
@@ -710,7 +714,7 @@ set_rel_consider_parallel(PlannerInfo *root, RelOptInfo *rel,
case RTE_VALUES:
/* Check for parallel-restricted functions. */
- if (!is_parallel_safe(root, (Node *) rte->values_lists))
+ if (!is_parallel_safe(root, (Node *) rte->values_lists, NULL))
return;
break;
@@ -747,18 +751,28 @@ set_rel_consider_parallel(PlannerInfo *root, RelOptInfo *rel,
* outer join clauses work correctly. It would likely break equivalence
* classes, too.
*/
- if (!is_parallel_safe(root, (Node *) rel->baserestrictinfo))
- return;
+ parallel_safe = is_parallel_safe(root, (Node *) rel->baserestrictinfo,
+ ¶llel_safe_except_in_params);
/*
* Likewise, if the relation's outputs are not parallel-safe, give up.
* (Usually, they're just Vars, but sometimes they're not.)
*/
- if (!is_parallel_safe(root, (Node *) rel->reltarget->exprs))
- return;
+ if (parallel_safe || parallel_safe_except_in_params)
+ {
+ bool target_parallel_safe;
+ bool target_parallel_safe_ignoring_params = false;
+
+ target_parallel_safe = is_parallel_safe(root,
+ (Node *) rel->reltarget->exprs,
+ &target_parallel_safe_ignoring_params);
+ parallel_safe = parallel_safe && target_parallel_safe;
+ parallel_safe_except_in_params = parallel_safe_except_in_params
+ && target_parallel_safe_ignoring_params;
+ }
- /* We have a winner. */
- rel->consider_parallel = true;
+ rel->consider_parallel = parallel_safe;
+ rel->consider_parallel_rechecking_params = parallel_safe_except_in_params;
}
/*
@@ -2277,9 +2291,21 @@ set_subquery_pathlist(PlannerInfo *root, RelOptInfo *rel,
pathkeys, required_outer));
}
+ /*
+ * XXX: As far as I can tell, the only time partial paths exist here
+ * is when we're going to execute multiple partial paths in parallel
+ * under a gather node (instead of executing paths serially under
+ * an append node). That means that the subquery scan path here
+ * is self-contained at this point -- so by definition it can't be
+ * reliant on lateral relids, which means we'll never have to consider
+ * rechecking params here.
+ */
+ Assert(!(rel->consider_parallel_rechecking_params && rel->partial_pathlist && !rel->consider_parallel));
+
/* If outer rel allows parallelism, do same for partial paths. */
if (rel->consider_parallel && bms_is_empty(required_outer))
{
+
/* If consider_parallel is false, there should be no partial paths. */
Assert(sub_final_rel->consider_parallel ||
sub_final_rel->partial_pathlist == NIL);
@@ -2633,7 +2659,7 @@ generate_gather_paths(PlannerInfo *root, RelOptInfo *rel, bool override_rows)
cheapest_partial_path->rows * cheapest_partial_path->parallel_workers;
simple_gather_path = (Path *)
create_gather_path(root, rel, cheapest_partial_path, rel->reltarget,
- NULL, rowsp);
+ rel->lateral_relids, rowsp);
add_path(rel, simple_gather_path);
/*
@@ -2650,7 +2676,7 @@ generate_gather_paths(PlannerInfo *root, RelOptInfo *rel, bool override_rows)
rows = subpath->rows * subpath->parallel_workers;
path = create_gather_merge_path(root, rel, subpath, rel->reltarget,
- subpath->pathkeys, NULL, rowsp);
+ subpath->pathkeys, rel->lateral_relids, rowsp);
add_path(rel, &path->path);
}
}
@@ -2752,11 +2778,15 @@ generate_useful_gather_paths(PlannerInfo *root, RelOptInfo *rel, bool override_r
double *rowsp = NULL;
List *useful_pathkeys_list = NIL;
Path *cheapest_partial_path = NULL;
+ Relids required_outer = rel->lateral_relids;
/* If there are no partial paths, there's nothing to do here. */
if (rel->partial_pathlist == NIL)
return;
+ if (!bms_is_subset(required_outer, rel->relids))
+ return;
+
/* Should we override the rel's rowcount estimate? */
if (override_rows)
rowsp = &rows;
@@ -2828,7 +2858,7 @@ generate_useful_gather_paths(PlannerInfo *root, RelOptInfo *rel, bool override_r
tmp,
rel->reltarget,
tmp->pathkeys,
- NULL,
+ required_outer,
rowsp);
add_path(rel, &path->path);
@@ -2862,7 +2892,7 @@ generate_useful_gather_paths(PlannerInfo *root, RelOptInfo *rel, bool override_r
tmp,
rel->reltarget,
tmp->pathkeys,
- NULL,
+ required_outer,
rowsp);
add_path(rel, &path->path);
@@ -3041,7 +3071,8 @@ standard_join_search(PlannerInfo *root, int levels_needed, List *initial_rels)
/*
* Except for the topmost scan/join rel, consider gathering
* partial paths. We'll do the same for the topmost scan/join rel
- * once we know the final targetlist (see grouping_planner).
+ * once we know the final targetlist (see
+ * apply_scanjoin_target_to_paths).
*/
if (lev < levels_needed)
generate_useful_gather_paths(root, rel, false);
diff --git a/src/backend/optimizer/path/equivclass.c b/src/backend/optimizer/path/equivclass.c
index 6f1abbe47d..4c176d2d49 100644
--- a/src/backend/optimizer/path/equivclass.c
+++ b/src/backend/optimizer/path/equivclass.c
@@ -897,7 +897,7 @@ find_computable_ec_member(PlannerInfo *root,
* check this last because it's a rather expensive test.
*/
if (require_parallel_safe &&
- !is_parallel_safe(root, (Node *) em->em_expr))
+ !is_parallel_safe(root, (Node *) em->em_expr, NULL))
continue;
return em; /* found usable expression */
@@ -1012,7 +1012,7 @@ relation_can_be_sorted_early(PlannerInfo *root, RelOptInfo *rel,
* check this last because it's a rather expensive test.
*/
if (require_parallel_safe &&
- !is_parallel_safe(root, (Node *) em->em_expr))
+ !is_parallel_safe(root, (Node *) em->em_expr, NULL))
continue;
return true;
diff --git a/src/backend/optimizer/path/indxpath.c b/src/backend/optimizer/path/indxpath.c
index 0e4e00eaf0..a094626248 100644
--- a/src/backend/optimizer/path/indxpath.c
+++ b/src/backend/optimizer/path/indxpath.c
@@ -1047,6 +1047,17 @@ build_index_paths(PlannerInfo *root, RelOptInfo *rel,
/*
* If appropriate, consider parallel index scan. We don't allow
* parallel index scan for bitmap index scans.
+ *
+ * XXX: Checking rel->consider_parallel_rechecking_params here resulted
+ * in some odd behavior on:
+ * select (select t.unique1 from tenk1 where tenk1.unique1 = t.unique1) from tenk1 t;
+ * where the total cost on the chosen plan went *up* considering
+ * the extra path.
+ *
+ * Current working theory is that this method is about base relation
+ * scans, and we only want parameterized paths to be parallelized as
+ * companions to existing parallel plans and so don't really care to
+ * consider a separate parallel index scan here.
*/
if (index->amcanparallel &&
rel->consider_parallel && outer_relids == NULL &&
@@ -1100,6 +1111,7 @@ build_index_paths(PlannerInfo *root, RelOptInfo *rel,
result = lappend(result, ipath);
/* If appropriate, consider parallel index scan */
+ /* XXX: As above here for rel->consider_parallel_rechecking_params? */
if (index->amcanparallel &&
rel->consider_parallel && outer_relids == NULL &&
scantype != ST_BITMAPSCAN)
diff --git a/src/backend/optimizer/path/joinpath.c b/src/backend/optimizer/path/joinpath.c
index 6407ede12a..f8daa7b265 100644
--- a/src/backend/optimizer/path/joinpath.c
+++ b/src/backend/optimizer/path/joinpath.c
@@ -722,6 +722,7 @@ try_partial_nestloop_path(PlannerInfo *root,
else
outerrelids = outerrel->relids;
+ /* TODO: recheck parallel safety here? */
if (!bms_is_subset(inner_paramrels, outerrelids))
return;
}
@@ -1746,16 +1747,24 @@ match_unsorted_outer(PlannerInfo *root,
* partial path and the joinrel is parallel-safe. However, we can't
* handle JOIN_UNIQUE_OUTER, because the outer path will be partial, and
* therefore we won't be able to properly guarantee uniqueness. Nor can
- * we handle joins needing lateral rels, since partial paths must not be
- * parameterized. Similarly, we can't handle JOIN_FULL and JOIN_RIGHT,
- * because they can produce false null extended rows.
+ * we handle JOIN_FULL and JOIN_RIGHT, because they can produce false null
+ * extended rows.
+ *
+ * Partial paths may only have parameters in limited cases
+ * where the parameterization is fully satisfied without sharing state
+ * between workers, so we only allow lateral rels on inputs to the join
+ * if the resulting join contains no lateral rels, the inner rel's laterals
+ * are fully satisfied by the outer rel, and the outer rel doesn't depend
+ * on the inner rel to produce any laterals.
*/
if (joinrel->consider_parallel &&
save_jointype != JOIN_UNIQUE_OUTER &&
save_jointype != JOIN_FULL &&
save_jointype != JOIN_RIGHT &&
outerrel->partial_pathlist != NIL &&
- bms_is_empty(joinrel->lateral_relids))
+ bms_is_empty(joinrel->lateral_relids) &&
+ bms_is_subset(innerrel->lateral_relids, outerrel->relids) &&
+ (bms_is_empty(outerrel->lateral_relids) || !bms_is_subset(outerrel->lateral_relids, innerrel->relids)))
{
if (nestjoinOK)
consider_parallel_nestloop(root, joinrel, outerrel, innerrel,
@@ -1870,7 +1879,9 @@ consider_parallel_nestloop(PlannerInfo *root,
Path *mpath;
/* Can't join to an inner path that is not parallel-safe */
- if (!innerpath->parallel_safe)
+ /* TODO: recheck parallel safety of params here? */
+ if (!innerpath->parallel_safe &&
+ !(innerpath->parallel_safe_ignoring_params))
continue;
/*
diff --git a/src/backend/optimizer/plan/createplan.c b/src/backend/optimizer/plan/createplan.c
index a5f6d678cc..e84834427b 100644
--- a/src/backend/optimizer/plan/createplan.c
+++ b/src/backend/optimizer/plan/createplan.c
@@ -5273,6 +5273,7 @@ copy_generic_path_info(Plan *dest, Path *src)
dest->plan_width = src->pathtarget->width;
dest->parallel_aware = src->parallel_aware;
dest->parallel_safe = src->parallel_safe;
+ dest->parallel_safe_ignoring_params = src->parallel_safe_ignoring_params;
}
/*
@@ -5290,6 +5291,7 @@ copy_plan_costsize(Plan *dest, Plan *src)
dest->parallel_aware = false;
/* Assume the inserted node is parallel-safe, if child plan is. */
dest->parallel_safe = src->parallel_safe;
+ dest->parallel_safe_ignoring_params = src->parallel_safe_ignoring_params;
}
/*
diff --git a/src/backend/optimizer/plan/planmain.c b/src/backend/optimizer/plan/planmain.c
index 273ac0acf7..bdbce2b87d 100644
--- a/src/backend/optimizer/plan/planmain.c
+++ b/src/backend/optimizer/plan/planmain.c
@@ -119,7 +119,7 @@ query_planner(PlannerInfo *root,
if (root->glob->parallelModeOK &&
force_parallel_mode != FORCE_PARALLEL_OFF)
final_rel->consider_parallel =
- is_parallel_safe(root, parse->jointree->quals);
+ is_parallel_safe(root, parse->jointree->quals, NULL);
/*
* The only path for it is a trivial Result path. We cheat a
diff --git a/src/backend/optimizer/plan/planner.c b/src/backend/optimizer/plan/planner.c
index 1e42d75465..008a096ee7 100644
--- a/src/backend/optimizer/plan/planner.c
+++ b/src/backend/optimizer/plan/planner.c
@@ -150,6 +150,7 @@ static RelOptInfo *create_grouping_paths(PlannerInfo *root,
RelOptInfo *input_rel,
PathTarget *target,
bool target_parallel_safe,
+ bool target_parallel_safe_ignoring_params,
grouping_sets_data *gd);
static bool is_degenerate_grouping(PlannerInfo *root);
static void create_degenerate_grouping_paths(PlannerInfo *root,
@@ -157,6 +158,7 @@ static void create_degenerate_grouping_paths(PlannerInfo *root,
RelOptInfo *grouped_rel);
static RelOptInfo *make_grouping_rel(PlannerInfo *root, RelOptInfo *input_rel,
PathTarget *target, bool target_parallel_safe,
+ bool target_parallel_safe_ignoring_params,
Node *havingQual);
static void create_ordinary_grouping_paths(PlannerInfo *root,
RelOptInfo *input_rel,
@@ -237,6 +239,7 @@ static void apply_scanjoin_target_to_paths(PlannerInfo *root,
List *scanjoin_targets,
List *scanjoin_targets_contain_srfs,
bool scanjoin_target_parallel_safe,
+ bool scanjoin_target_parallel_safe_ignoring_params,
bool tlist_same_exprs);
static void create_partitionwise_grouping_paths(PlannerInfo *root,
RelOptInfo *input_rel,
@@ -1241,6 +1244,7 @@ grouping_planner(PlannerInfo *root, double tuple_fraction)
List *final_targets;
List *final_targets_contain_srfs;
bool final_target_parallel_safe;
+ bool final_target_parallel_safe_ignoring_params = false;
RelOptInfo *current_rel;
RelOptInfo *final_rel;
FinalPathExtraData extra;
@@ -1303,7 +1307,7 @@ grouping_planner(PlannerInfo *root, double tuple_fraction)
/* And check whether it's parallel safe */
final_target_parallel_safe =
- is_parallel_safe(root, (Node *) final_target->exprs);
+ is_parallel_safe(root, (Node *) final_target->exprs, &final_target_parallel_safe_ignoring_params);
/* The setop result tlist couldn't contain any SRFs */
Assert(!parse->hasTargetSRFs);
@@ -1337,14 +1341,17 @@ grouping_planner(PlannerInfo *root, double tuple_fraction)
List *sort_input_targets;
List *sort_input_targets_contain_srfs;
bool sort_input_target_parallel_safe;
+ bool sort_input_target_parallel_safe_ignoring_params = false;
PathTarget *grouping_target;
List *grouping_targets;
List *grouping_targets_contain_srfs;
bool grouping_target_parallel_safe;
+ bool grouping_target_parallel_safe_ignoring_params = false;
PathTarget *scanjoin_target;
List *scanjoin_targets;
List *scanjoin_targets_contain_srfs;
bool scanjoin_target_parallel_safe;
+ bool scanjoin_target_parallel_safe_ignoring_params = false;
bool scanjoin_target_same_exprs;
bool have_grouping;
WindowFuncLists *wflists = NULL;
@@ -1457,7 +1464,7 @@ grouping_planner(PlannerInfo *root, double tuple_fraction)
*/
final_target = create_pathtarget(root, root->processed_tlist);
final_target_parallel_safe =
- is_parallel_safe(root, (Node *) final_target->exprs);
+ is_parallel_safe(root, (Node *) final_target->exprs, &final_target_parallel_safe_ignoring_params);
/*
* If ORDER BY was given, consider whether we should use a post-sort
@@ -1470,12 +1477,13 @@ grouping_planner(PlannerInfo *root, double tuple_fraction)
final_target,
&have_postponed_srfs);
sort_input_target_parallel_safe =
- is_parallel_safe(root, (Node *) sort_input_target->exprs);
+ is_parallel_safe(root, (Node *) sort_input_target->exprs, &sort_input_target_parallel_safe_ignoring_params);
}
else
{
sort_input_target = final_target;
sort_input_target_parallel_safe = final_target_parallel_safe;
+ sort_input_target_parallel_safe_ignoring_params = final_target_parallel_safe_ignoring_params;
}
/*
@@ -1489,12 +1497,13 @@ grouping_planner(PlannerInfo *root, double tuple_fraction)
final_target,
activeWindows);
grouping_target_parallel_safe =
- is_parallel_safe(root, (Node *) grouping_target->exprs);
+ is_parallel_safe(root, (Node *) grouping_target->exprs, &grouping_target_parallel_safe_ignoring_params);
}
else
{
grouping_target = sort_input_target;
grouping_target_parallel_safe = sort_input_target_parallel_safe;
+ grouping_target_parallel_safe_ignoring_params = sort_input_target_parallel_safe_ignoring_params;
}
/*
@@ -1508,12 +1517,13 @@ grouping_planner(PlannerInfo *root, double tuple_fraction)
{
scanjoin_target = make_group_input_target(root, final_target);
scanjoin_target_parallel_safe =
- is_parallel_safe(root, (Node *) scanjoin_target->exprs);
+ is_parallel_safe(root, (Node *) scanjoin_target->exprs, &scanjoin_target_parallel_safe_ignoring_params);
}
else
{
scanjoin_target = grouping_target;
scanjoin_target_parallel_safe = grouping_target_parallel_safe;
+ scanjoin_target_parallel_safe_ignoring_params = grouping_target_parallel_safe_ignoring_params;
}
/*
@@ -1565,6 +1575,7 @@ grouping_planner(PlannerInfo *root, double tuple_fraction)
apply_scanjoin_target_to_paths(root, current_rel, scanjoin_targets,
scanjoin_targets_contain_srfs,
scanjoin_target_parallel_safe,
+ scanjoin_target_parallel_safe_ignoring_params,
scanjoin_target_same_exprs);
/*
@@ -1592,6 +1603,7 @@ grouping_planner(PlannerInfo *root, double tuple_fraction)
current_rel,
grouping_target,
grouping_target_parallel_safe,
+ grouping_target_parallel_safe_ignoring_params,
gset_data);
/* Fix things up if grouping_target contains SRFs */
if (parse->hasTargetSRFs)
@@ -1665,10 +1677,25 @@ grouping_planner(PlannerInfo *root, double tuple_fraction)
* not a SELECT, consider_parallel will be false for every relation in the
* query.
*/
- if (current_rel->consider_parallel &&
- is_parallel_safe(root, parse->limitOffset) &&
- is_parallel_safe(root, parse->limitCount))
- final_rel->consider_parallel = true;
+ if (current_rel->consider_parallel || current_rel->consider_parallel_rechecking_params)
+ {
+ bool limit_count_parallel_safe;
+ bool limit_offset_parallel_safe;
+ bool limit_count_parallel_safe_ignoring_params = false;
+ bool limit_offset_parallel_safe_ignoring_params = false;
+
+ limit_count_parallel_safe = is_parallel_safe(root, parse->limitCount, &limit_count_parallel_safe_ignoring_params);
+ limit_offset_parallel_safe = is_parallel_safe(root, parse->limitOffset, &limit_offset_parallel_safe_ignoring_params);
+
+ if (current_rel->consider_parallel &&
+ limit_count_parallel_safe &&
+ limit_offset_parallel_safe)
+ final_rel->consider_parallel = true;
+ if (current_rel->consider_parallel_rechecking_params &&
+ limit_count_parallel_safe_ignoring_params &&
+ limit_offset_parallel_safe_ignoring_params)
+ final_rel->consider_parallel_rechecking_params = true;
+ }
/*
* If the current_rel belongs to a single FDW, so does the final_rel.
@@ -1869,8 +1896,8 @@ grouping_planner(PlannerInfo *root, double tuple_fraction)
* Generate partial paths for final_rel, too, if outer query levels might
* be able to make use of them.
*/
- if (final_rel->consider_parallel && root->query_level > 1 &&
- !limit_needed(parse))
+ if ((final_rel->consider_parallel || final_rel->consider_parallel_rechecking_params) &&
+ root->query_level > 1 && !limit_needed(parse))
{
Assert(!parse->rowMarks && parse->commandType == CMD_SELECT);
foreach(lc, current_rel->partial_pathlist)
@@ -3282,6 +3309,7 @@ create_grouping_paths(PlannerInfo *root,
RelOptInfo *input_rel,
PathTarget *target,
bool target_parallel_safe,
+ bool target_parallel_safe_ignoring_params,
grouping_sets_data *gd)
{
Query *parse = root->parse;
@@ -3297,7 +3325,9 @@ create_grouping_paths(PlannerInfo *root,
* aggregation paths.
*/
grouped_rel = make_grouping_rel(root, input_rel, target,
- target_parallel_safe, parse->havingQual);
+ target_parallel_safe,
+ target_parallel_safe_ignoring_params,
+ parse->havingQual);
/*
* Create either paths for a degenerate grouping or paths for ordinary
@@ -3358,6 +3388,7 @@ create_grouping_paths(PlannerInfo *root,
extra.flags = flags;
extra.target_parallel_safe = target_parallel_safe;
+ extra.target_parallel_safe_ignoring_params = target_parallel_safe_ignoring_params;
extra.havingQual = parse->havingQual;
extra.targetList = parse->targetList;
extra.partial_costs_set = false;
@@ -3393,7 +3424,7 @@ create_grouping_paths(PlannerInfo *root,
static RelOptInfo *
make_grouping_rel(PlannerInfo *root, RelOptInfo *input_rel,
PathTarget *target, bool target_parallel_safe,
- Node *havingQual)
+ bool target_parallel_safe_ignoring_params, Node *havingQual)
{
RelOptInfo *grouped_rel;
@@ -3421,9 +3452,21 @@ make_grouping_rel(PlannerInfo *root, RelOptInfo *input_rel,
* can't be parallel-safe, either. Otherwise, it's parallel-safe if the
* target list and HAVING quals are parallel-safe.
*/
- if (input_rel->consider_parallel && target_parallel_safe &&
- is_parallel_safe(root, (Node *) havingQual))
- grouped_rel->consider_parallel = true;
+ if ((input_rel->consider_parallel || input_rel->consider_parallel_rechecking_params)
+ && (target_parallel_safe || target_parallel_safe_ignoring_params))
+ {
+ bool having_qual_parallel_safe;
+ bool having_qual_parallel_safe_ignoring_params = false;
+
+ having_qual_parallel_safe = is_parallel_safe(root, (Node *) havingQual,
+ &having_qual_parallel_safe_ignoring_params);
+
+ grouped_rel->consider_parallel = input_rel->consider_parallel &&
+ having_qual_parallel_safe && target_parallel_safe;
+ grouped_rel->consider_parallel_rechecking_params =
+ input_rel->consider_parallel_rechecking_params &&
+ having_qual_parallel_safe_ignoring_params && target_parallel_safe_ignoring_params;
+ }
/*
* If the input rel belongs to a single FDW, so does the grouped rel.
@@ -4050,7 +4093,7 @@ create_window_paths(PlannerInfo *root,
* target list and active windows for non-parallel-safe constructs.
*/
if (input_rel->consider_parallel && output_target_parallel_safe &&
- is_parallel_safe(root, (Node *) activeWindows))
+ is_parallel_safe(root, (Node *) activeWindows, NULL))
window_rel->consider_parallel = true;
/*
@@ -5755,6 +5798,7 @@ adjust_paths_for_srfs(PlannerInfo *root, RelOptInfo *rel,
PathTarget *thistarget = lfirst_node(PathTarget, lc1);
bool contains_srfs = (bool) lfirst_int(lc2);
+ /* TODO: How do we know the new target is parallel safe? */
/* If this level doesn't contain SRFs, do regular projection */
if (contains_srfs)
newpath = (Path *) create_set_projection_path(root,
@@ -6071,8 +6115,8 @@ plan_create_index_workers(Oid tableOid, Oid indexOid)
* safe.
*/
if (heap->rd_rel->relpersistence == RELPERSISTENCE_TEMP ||
- !is_parallel_safe(root, (Node *) RelationGetIndexExpressions(index)) ||
- !is_parallel_safe(root, (Node *) RelationGetIndexPredicate(index)))
+ !is_parallel_safe(root, (Node *) RelationGetIndexExpressions(index), NULL) ||
+ !is_parallel_safe(root, (Node *) RelationGetIndexPredicate(index), NULL))
{
parallel_workers = 0;
goto done;
@@ -6535,6 +6579,8 @@ create_partial_grouping_paths(PlannerInfo *root,
grouped_rel->relids);
partially_grouped_rel->consider_parallel =
grouped_rel->consider_parallel;
+ partially_grouped_rel->consider_parallel_rechecking_params =
+ grouped_rel->consider_parallel_rechecking_params;
partially_grouped_rel->reloptkind = grouped_rel->reloptkind;
partially_grouped_rel->serverid = grouped_rel->serverid;
partially_grouped_rel->userid = grouped_rel->userid;
@@ -6998,6 +7044,7 @@ apply_scanjoin_target_to_paths(PlannerInfo *root,
List *scanjoin_targets,
List *scanjoin_targets_contain_srfs,
bool scanjoin_target_parallel_safe,
+ bool scanjoin_target_parallel_safe_ignoring_params,
bool tlist_same_exprs)
{
bool rel_is_partitioned = IS_PARTITIONED_REL(rel);
@@ -7007,6 +7054,11 @@ apply_scanjoin_target_to_paths(PlannerInfo *root,
/* This recurses, so be paranoid. */
check_stack_depth();
+ /*
+ * TOOD: when/how do we want to generate gather paths if
+ * scanjoin_target_parallel_safe_ignoring_params = true
+ */
+
/*
* If the rel is partitioned, we want to drop its existing paths and
* generate new ones. This function would still be correct if we kept the
@@ -7047,6 +7099,67 @@ apply_scanjoin_target_to_paths(PlannerInfo *root,
generate_useful_gather_paths(root, rel, false);
/* Can't use parallel query above this level. */
+
+ /*
+ * There are cases where:
+ * (rel->consider_parallel &&
+ * !scanjoin_target_parallel_safe &&
+ * scanjoin_target_parallel_safe_ignoring_params)
+ * is true at this point. See longer commment below.
+ */
+ if (!(rel->consider_parallel_rechecking_params && scanjoin_target_parallel_safe_ignoring_params))
+ {
+ /*
+ * TODO: if we limit setting:
+ *
+ * rel->consider_parallel_rechecking_params = false
+ * rel->partial_pathlist = NIL
+ *
+ * to this condition, we're pushing off the checks as to whether or
+ * not a given param usage is safe in the context of a given path
+ * (in the context of a given rel?). That almost certainly means
+ * we'd have to add other checks later (maybe just on
+ * lateral/relids and not parallel safety overall), because at the
+ * end of grouping_planner() we copy partial paths to the
+ * final_rel, and while that path may be acceptable in some
+ * contexts it may not be in all contexts.
+ *
+ * OTOH if we're only dependent on PARAM_EXEC params, and we already
+ * know that subpath->param_info == NULL holds (and that seems like
+ * it must since we were going to replace the path target anyway...
+ * though the one caveat is from the original form of this function
+ * we'd only ever actually assert that for paths not partial paths)
+ * then if a param shows up in the target why would it not be parallel
+ * safe.
+ *
+ * Adding to the mystery even with the original form of this function
+ * we still end up with parallel paths where I'd expect this to
+ * disallow them. For example:
+ *
+ * SELECT '' AS six, f1 AS "Correlated Field", f3 AS "Second Field"
+ * FROM SUBSELECT_TBL upper
+ * WHERE f3 IN (
+ * SELECT upper.f1 + f2
+ * FROM SUBSELECT_TBL
+ * WHERE f2 = CAST(f3 AS integer)
+ * );
+ *
+ * ends up with the correlated query underneath parallel plan despite
+ * its target containing a param, and therefore this function marking
+ * the rel as consider_parallel=false and removing the partial paths.
+ *
+ * But the plan as a whole is parallel safe, and so the subplan is also
+ * parallel safe, which means we can incorporate it into a full parallel
+ * plan. In other words, this is a parallel safe, but not parallel aware
+ * subplan (and regular, not parallel, seq scan inside that subplan).
+ * It's not a partial path; it's a full path that is executed as a subquery.
+ *
+ * Current conclusion: it's fine for subplans, which is the case we're
+ * currently targeting anyway. And it might even be the only case that
+ * matters at all.
+ */
+ }
+ rel->consider_parallel_rechecking_params = false;
rel->partial_pathlist = NIL;
rel->consider_parallel = false;
}
@@ -7182,6 +7295,7 @@ apply_scanjoin_target_to_paths(PlannerInfo *root,
child_scanjoin_targets,
scanjoin_targets_contain_srfs,
scanjoin_target_parallel_safe,
+ scanjoin_target_parallel_safe_ignoring_params,
tlist_same_exprs);
/* Save non-dummy children for Append paths. */
@@ -7199,6 +7313,11 @@ apply_scanjoin_target_to_paths(PlannerInfo *root,
* avoid creating multiple Gather nodes within the same plan. We must do
* this after all paths have been generated and before set_cheapest, since
* one of the generated paths may turn out to be the cheapest one.
+ *
+ * TODO: This is the same problem as earlier in this function: when allowing
+ * "parallel safe ignoring params" paths here we don't actually know we are
+ * safe in any possible context just possibly safe in the context of the
+ * right rel.
*/
if (rel->consider_parallel && !IS_OTHER_REL(rel))
generate_useful_gather_paths(root, rel, false);
@@ -7306,6 +7425,7 @@ create_partitionwise_grouping_paths(PlannerInfo *root,
child_grouped_rel = make_grouping_rel(root, child_input_rel,
child_target,
extra->target_parallel_safe,
+ extra->target_parallel_safe_ignoring_params,
child_extra.havingQual);
/* Create grouping paths for this child relation. */
diff --git a/src/backend/optimizer/plan/subselect.c b/src/backend/optimizer/plan/subselect.c
index c9f7a09d10..393db3b42d 100644
--- a/src/backend/optimizer/plan/subselect.c
+++ b/src/backend/optimizer/plan/subselect.c
@@ -342,6 +342,7 @@ build_subplan(PlannerInfo *root, Plan *plan, PlannerInfo *subroot,
splan->useHashTable = false;
splan->unknownEqFalse = unknownEqFalse;
splan->parallel_safe = plan->parallel_safe;
+ splan->parallel_safe_ignoring_params = plan->parallel_safe_ignoring_params;
splan->setParam = NIL;
splan->parParam = NIL;
splan->args = NIL;
@@ -1937,6 +1938,7 @@ process_sublinks_mutator(Node *node, process_sublinks_context *context)
{
SubLink *sublink = (SubLink *) node;
Node *testexpr;
+ Node *result;
/*
* First, recursively process the lefthand-side expressions, if any.
@@ -1948,12 +1950,29 @@ process_sublinks_mutator(Node *node, process_sublinks_context *context)
/*
* Now build the SubPlan node and make the expr to return.
*/
- return make_subplan(context->root,
+ result = make_subplan(context->root,
(Query *) sublink->subselect,
sublink->subLinkType,
sublink->subLinkId,
testexpr,
context->isTopQual);
+
+ /*
+ * If planning determined that a subpath was parallel safe as long
+ * as required params are provided by each individual worker then we
+ * can mark the resulting subplan actually parallel safe since we now
+ * know for certain how that path will be used.
+ */
+ if (IsA(result, SubPlan) && !((SubPlan*)result)->parallel_safe
+ && ((SubPlan*)result)->parallel_safe_ignoring_params
+ && enable_parallel_params_recheck)
+ {
+ Plan *subplan = planner_subplan_get_plan(context->root, (SubPlan*)result);
+ ((SubPlan*)result)->parallel_safe = is_parallel_safe(context->root, testexpr, NULL);
+ subplan->parallel_safe = ((SubPlan*)result)->parallel_safe;
+ }
+
+ return result;
}
/*
diff --git a/src/backend/optimizer/prep/prepunion.c b/src/backend/optimizer/prep/prepunion.c
index e9256a2d4d..16cb35c914 100644
--- a/src/backend/optimizer/prep/prepunion.c
+++ b/src/backend/optimizer/prep/prepunion.c
@@ -409,6 +409,7 @@ recurse_set_operations(Node *setOp, PlannerInfo *root,
Assert(subpath->param_info == NULL);
/* avoid apply_projection_to_path, in case of multiple refs */
+ /* TODO: how to we know the target is parallel safe? */
path = (Path *) create_projection_path(root, subpath->parent,
subpath, target);
lfirst(lc) = path;
diff --git a/src/backend/optimizer/util/clauses.c b/src/backend/optimizer/util/clauses.c
index 3412d31117..e2cf335f4a 100644
--- a/src/backend/optimizer/util/clauses.c
+++ b/src/backend/optimizer/util/clauses.c
@@ -55,6 +55,15 @@
#include "utils/syscache.h"
#include "utils/typcache.h"
+bool enable_parallel_params_recheck = true;
+
+typedef struct
+{
+ PlannerInfo *root;
+ AggSplit aggsplit;
+ AggClauseCosts *costs;
+} get_agg_clause_costs_context;
+
typedef struct
{
ParamListInfo boundParams;
@@ -88,6 +97,8 @@ typedef struct
{
char max_hazard; /* worst proparallel hazard found so far */
char max_interesting; /* worst proparallel hazard of interest */
+ char max_hazard_ignoring_params;
+ bool check_params_independently;
List *safe_param_ids; /* PARAM_EXEC Param IDs to treat as safe */
} max_parallel_hazard_context;
@@ -624,19 +635,27 @@ max_parallel_hazard(Query *parse)
context.max_hazard = PROPARALLEL_SAFE;
context.max_interesting = PROPARALLEL_UNSAFE;
context.safe_param_ids = NIL;
+ context.check_params_independently = false;
(void) max_parallel_hazard_walker((Node *) parse, &context);
return context.max_hazard;
}
/*
* is_parallel_safe
- * Detect whether the given expr contains only parallel-safe functions
+ * Detect whether the given expr contains only parallel safe funcions
+ * XXX: It does more than functions?
+ *
+ * If provided, safe_ignoring_params will be set the result of running the same
+ * parallel safety checks with the exception that params will be allowed. This
+ * value is useful since params are not inherently parallel unsafe, but rather
+ * their usage context (whether or not the worker is able to provide the value)
+ * determines parallel safety.
*
* root->glob->maxParallelHazard must previously have been set to the
- * result of max_parallel_hazard() on the whole query.
+ * result of max_parallel_hazard() on the whole query
*/
bool
-is_parallel_safe(PlannerInfo *root, Node *node)
+is_parallel_safe(PlannerInfo *root, Node *node, bool *safe_ignoring_params)
{
max_parallel_hazard_context context;
PlannerInfo *proot;
@@ -653,8 +672,10 @@ is_parallel_safe(PlannerInfo *root, Node *node)
return true;
/* Else use max_parallel_hazard's search logic, but stop on RESTRICTED */
context.max_hazard = PROPARALLEL_SAFE;
+ context.max_hazard_ignoring_params = PROPARALLEL_SAFE;
context.max_interesting = PROPARALLEL_RESTRICTED;
context.safe_param_ids = NIL;
+ context.check_params_independently = safe_ignoring_params != NULL;
/*
* The params that refer to the same or parent query level are considered
@@ -672,12 +693,17 @@ is_parallel_safe(PlannerInfo *root, Node *node)
}
}
- return !max_parallel_hazard_walker(node, &context);
+ (void) max_parallel_hazard_walker(node, &context);
+
+ if (safe_ignoring_params)
+ *safe_ignoring_params = context.max_hazard_ignoring_params == PROPARALLEL_SAFE;
+
+ return context.max_hazard == PROPARALLEL_SAFE;
}
/* core logic for all parallel-hazard checks */
static bool
-max_parallel_hazard_test(char proparallel, max_parallel_hazard_context *context)
+max_parallel_hazard_test(char proparallel, max_parallel_hazard_context *context, bool from_param)
{
switch (proparallel)
{
@@ -688,12 +714,16 @@ max_parallel_hazard_test(char proparallel, max_parallel_hazard_context *context)
/* increase max_hazard to RESTRICTED */
Assert(context->max_hazard != PROPARALLEL_UNSAFE);
context->max_hazard = proparallel;
+ if (!from_param)
+ context->max_hazard_ignoring_params = proparallel;
/* done if we are not expecting any unsafe functions */
if (context->max_interesting == proparallel)
return true;
break;
case PROPARALLEL_UNSAFE:
context->max_hazard = proparallel;
+ if (!from_param)
+ context->max_hazard_ignoring_params = proparallel;
/* we're always done at the first unsafe construct */
return true;
default:
@@ -708,7 +738,41 @@ static bool
max_parallel_hazard_checker(Oid func_id, void *context)
{
return max_parallel_hazard_test(func_parallel(func_id),
- (max_parallel_hazard_context *) context);
+ (max_parallel_hazard_context *) context, false);
+}
+
+static bool
+max_parallel_hazard_walker_can_short_circuit(max_parallel_hazard_context *context)
+{
+ if (!context->check_params_independently)
+ return true;
+
+ switch (context->max_hazard)
+ {
+ case PROPARALLEL_SAFE:
+ /* nothing to see here, move along */
+ break;
+ case PROPARALLEL_RESTRICTED:
+ if (context->max_interesting == PROPARALLEL_RESTRICTED)
+ return context->max_hazard_ignoring_params != PROPARALLEL_SAFE;
+
+ /*
+ * We haven't even met our max interesting yet, so
+ * we certainly can't short-circuit.
+ */
+ break;
+ case PROPARALLEL_UNSAFE:
+ if (context->max_interesting == PROPARALLEL_RESTRICTED)
+ return context->max_hazard_ignoring_params != PROPARALLEL_SAFE;
+ else if (context->max_interesting == PROPARALLEL_UNSAFE)
+ return context->max_hazard_ignoring_params == PROPARALLEL_UNSAFE;
+
+ break;
+ default:
+ elog(ERROR, "unrecognized proparallel value \"%c\"", context->max_hazard);
+ break;
+ }
+ return false;
}
static bool
@@ -720,7 +784,7 @@ max_parallel_hazard_walker(Node *node, max_parallel_hazard_context *context)
/* Check for hazardous functions in node itself */
if (check_functions_in_node(node, max_parallel_hazard_checker,
context))
- return true;
+ return max_parallel_hazard_walker_can_short_circuit(context);
/*
* It should be OK to treat MinMaxExpr as parallel-safe, since btree
@@ -735,14 +799,14 @@ max_parallel_hazard_walker(Node *node, max_parallel_hazard_context *context)
*/
if (IsA(node, CoerceToDomain))
{
- if (max_parallel_hazard_test(PROPARALLEL_RESTRICTED, context))
- return true;
+ if (max_parallel_hazard_test(PROPARALLEL_RESTRICTED, context, false))
+ return max_parallel_hazard_walker_can_short_circuit(context);
}
else if (IsA(node, NextValueExpr))
{
- if (max_parallel_hazard_test(PROPARALLEL_UNSAFE, context))
- return true;
+ if (max_parallel_hazard_test(PROPARALLEL_UNSAFE, context, false))
+ return max_parallel_hazard_walker_can_short_circuit(context);
}
/*
@@ -755,8 +819,8 @@ max_parallel_hazard_walker(Node *node, max_parallel_hazard_context *context)
*/
else if (IsA(node, WindowFunc))
{
- if (max_parallel_hazard_test(PROPARALLEL_RESTRICTED, context))
- return true;
+ if (max_parallel_hazard_test(PROPARALLEL_RESTRICTED, context, false))
+ return max_parallel_hazard_walker_can_short_circuit(context);
}
/*
@@ -775,8 +839,8 @@ max_parallel_hazard_walker(Node *node, max_parallel_hazard_context *context)
*/
else if (IsA(node, SubLink))
{
- if (max_parallel_hazard_test(PROPARALLEL_RESTRICTED, context))
- return true;
+ if (max_parallel_hazard_test(PROPARALLEL_RESTRICTED, context, false))
+ return max_parallel_hazard_walker_can_short_circuit(context);
}
/*
@@ -791,18 +855,23 @@ max_parallel_hazard_walker(Node *node, max_parallel_hazard_context *context)
List *save_safe_param_ids;
if (!subplan->parallel_safe &&
- max_parallel_hazard_test(PROPARALLEL_RESTRICTED, context))
+ (!enable_parallel_params_recheck || !subplan->parallel_safe_ignoring_params) &&
+ max_parallel_hazard_test(PROPARALLEL_RESTRICTED, context, false) &&
+ max_parallel_hazard_walker_can_short_circuit(context))
return true;
save_safe_param_ids = context->safe_param_ids;
context->safe_param_ids = list_concat_copy(context->safe_param_ids,
subplan->paramIds);
- if (max_parallel_hazard_walker(subplan->testexpr, context))
- return true; /* no need to restore safe_param_ids */
+ if (max_parallel_hazard_walker(subplan->testexpr, context) &&
+ max_parallel_hazard_walker_can_short_circuit(context))
+ /* no need to restore safe_param_ids */
+ return true;
+
list_free(context->safe_param_ids);
context->safe_param_ids = save_safe_param_ids;
/* we must also check args, but no special Param treatment there */
if (max_parallel_hazard_walker((Node *) subplan->args, context))
- return true;
+ return max_parallel_hazard_walker_can_short_circuit(context);
/* don't want to recurse normally, so we're done */
return false;
}
@@ -824,8 +893,8 @@ max_parallel_hazard_walker(Node *node, max_parallel_hazard_context *context)
if (param->paramkind != PARAM_EXEC ||
!list_member_int(context->safe_param_ids, param->paramid))
{
- if (max_parallel_hazard_test(PROPARALLEL_RESTRICTED, context))
- return true;
+ if (max_parallel_hazard_test(PROPARALLEL_RESTRICTED, context, true))
+ return max_parallel_hazard_walker_can_short_circuit(context);
}
return false; /* nothing to recurse to */
}
@@ -843,7 +912,7 @@ max_parallel_hazard_walker(Node *node, max_parallel_hazard_context *context)
if (query->rowMarks != NULL)
{
context->max_hazard = PROPARALLEL_UNSAFE;
- return true;
+ return max_parallel_hazard_walker_can_short_circuit(context);
}
/* Recurse into subselects */
diff --git a/src/backend/optimizer/util/pathnode.c b/src/backend/optimizer/util/pathnode.c
index a53850b370..21be3824c1 100644
--- a/src/backend/optimizer/util/pathnode.c
+++ b/src/backend/optimizer/util/pathnode.c
@@ -756,10 +756,10 @@ add_partial_path(RelOptInfo *parent_rel, Path *new_path)
CHECK_FOR_INTERRUPTS();
/* Path to be added must be parallel safe. */
- Assert(new_path->parallel_safe);
+ Assert(new_path->parallel_safe || new_path->parallel_safe_ignoring_params);
/* Relation should be OK for parallelism, too. */
- Assert(parent_rel->consider_parallel);
+ Assert(parent_rel->consider_parallel || parent_rel->consider_parallel_rechecking_params);
/*
* As in add_path, throw out any paths which are dominated by the new
@@ -938,6 +938,7 @@ create_seqscan_path(PlannerInfo *root, RelOptInfo *rel,
required_outer);
pathnode->parallel_aware = parallel_workers > 0 ? true : false;
pathnode->parallel_safe = rel->consider_parallel;
+ pathnode->parallel_safe_ignoring_params = rel->consider_parallel_rechecking_params;
pathnode->parallel_workers = parallel_workers;
pathnode->pathkeys = NIL; /* seqscan has unordered result */
@@ -1016,6 +1017,7 @@ create_index_path(PlannerInfo *root,
required_outer);
pathnode->path.parallel_aware = false;
pathnode->path.parallel_safe = rel->consider_parallel;
+ pathnode->path.parallel_safe_ignoring_params = rel->consider_parallel_rechecking_params;
pathnode->path.parallel_workers = 0;
pathnode->path.pathkeys = pathkeys;
@@ -1865,7 +1867,7 @@ create_gather_merge_path(PlannerInfo *root, RelOptInfo *rel, Path *subpath,
Cost input_startup_cost = 0;
Cost input_total_cost = 0;
- Assert(subpath->parallel_safe);
+ Assert(subpath->parallel_safe || subpath->parallel_safe_ignoring_params);
Assert(pathkeys);
pathnode->path.pathtype = T_GatherMerge;
@@ -1953,7 +1955,7 @@ create_gather_path(PlannerInfo *root, RelOptInfo *rel, Path *subpath,
{
GatherPath *pathnode = makeNode(GatherPath);
- Assert(subpath->parallel_safe);
+ Assert(subpath->parallel_safe || subpath->parallel_safe_ignoring_params);
pathnode->path.pathtype = T_Gather;
pathnode->path.parent = rel;
@@ -2000,6 +2002,8 @@ create_subqueryscan_path(PlannerInfo *root, RelOptInfo *rel, Path *subpath,
pathnode->path.parallel_aware = false;
pathnode->path.parallel_safe = rel->consider_parallel &&
subpath->parallel_safe;
+ pathnode->path.parallel_safe_ignoring_params = rel->consider_parallel_rechecking_params &&
+ subpath->parallel_safe_ignoring_params;
pathnode->path.parallel_workers = subpath->parallel_workers;
pathnode->path.pathkeys = pathkeys;
pathnode->subpath = subpath;
@@ -2417,6 +2421,8 @@ create_nestloop_path(PlannerInfo *root,
NestPath *pathnode = makeNode(NestPath);
Relids inner_req_outer = PATH_REQ_OUTER(inner_path);
+ /* TODO: Assert lateral relids subset safety? */
+
/*
* If the inner path is parameterized by the outer, we must drop any
* restrict_clauses that are due to be moved into the inner path. We have
@@ -2457,6 +2463,8 @@ create_nestloop_path(PlannerInfo *root,
pathnode->jpath.path.parallel_aware = false;
pathnode->jpath.path.parallel_safe = joinrel->consider_parallel &&
outer_path->parallel_safe && inner_path->parallel_safe;
+ pathnode->jpath.path.parallel_safe_ignoring_params = joinrel->consider_parallel_rechecking_params &&
+ outer_path->parallel_safe_ignoring_params && inner_path->parallel_safe_ignoring_params;
/* This is a foolish way to estimate parallel_workers, but for now... */
pathnode->jpath.path.parallel_workers = outer_path->parallel_workers;
pathnode->jpath.path.pathkeys = pathkeys;
@@ -2630,6 +2638,8 @@ create_projection_path(PlannerInfo *root,
{
ProjectionPath *pathnode = makeNode(ProjectionPath);
PathTarget *oldtarget;
+ bool target_parallel_safe;
+ bool target_parallel_safe_ignoring_params = false;
/*
* We mustn't put a ProjectionPath directly above another; it's useless
@@ -2653,9 +2663,12 @@ create_projection_path(PlannerInfo *root,
/* For now, assume we are above any joins, so no parameterization */
pathnode->path.param_info = NULL;
pathnode->path.parallel_aware = false;
+ target_parallel_safe = is_parallel_safe(root, (Node *) target->exprs,
+ &target_parallel_safe_ignoring_params);
pathnode->path.parallel_safe = rel->consider_parallel &&
- subpath->parallel_safe &&
- is_parallel_safe(root, (Node *) target->exprs);
+ subpath->parallel_safe && target_parallel_safe;
+ pathnode->path.parallel_safe_ignoring_params = rel->consider_parallel_rechecking_params &&
+ subpath->parallel_safe_ignoring_params && target_parallel_safe_ignoring_params;
pathnode->path.parallel_workers = subpath->parallel_workers;
/* Projection does not change the sort order */
pathnode->path.pathkeys = subpath->pathkeys;
@@ -2763,7 +2776,7 @@ apply_projection_to_path(PlannerInfo *root,
* parallel-safe in the target expressions, then we can't.
*/
if ((IsA(path, GatherPath) || IsA(path, GatherMergePath)) &&
- is_parallel_safe(root, (Node *) target->exprs))
+ is_parallel_safe(root, (Node *) target->exprs, NULL))
{
/*
* We always use create_projection_path here, even if the subpath is
@@ -2797,7 +2810,7 @@ apply_projection_to_path(PlannerInfo *root,
}
}
else if (path->parallel_safe &&
- !is_parallel_safe(root, (Node *) target->exprs))
+ !is_parallel_safe(root, (Node *) target->exprs, NULL))
{
/*
* We're inserting a parallel-restricted target list into a path
@@ -2805,6 +2818,7 @@ apply_projection_to_path(PlannerInfo *root,
* safe.
*/
path->parallel_safe = false;
+ path->parallel_safe_ignoring_params = false; /* TODO */
}
return path;
@@ -2837,7 +2851,7 @@ create_set_projection_path(PlannerInfo *root,
pathnode->path.parallel_aware = false;
pathnode->path.parallel_safe = rel->consider_parallel &&
subpath->parallel_safe &&
- is_parallel_safe(root, (Node *) target->exprs);
+ is_parallel_safe(root, (Node *) target->exprs, NULL);
pathnode->path.parallel_workers = subpath->parallel_workers;
/* Projection does not change the sort order XXX? */
pathnode->path.pathkeys = subpath->pathkeys;
@@ -3114,6 +3128,8 @@ create_agg_path(PlannerInfo *root,
pathnode->path.parallel_aware = false;
pathnode->path.parallel_safe = rel->consider_parallel &&
subpath->parallel_safe;
+ pathnode->path.parallel_safe_ignoring_params = rel->consider_parallel_rechecking_params &&
+ subpath->parallel_safe_ignoring_params;
pathnode->path.parallel_workers = subpath->parallel_workers;
if (aggstrategy == AGG_SORTED)
pathnode->path.pathkeys = subpath->pathkeys; /* preserves order */
@@ -3735,6 +3751,8 @@ create_limit_path(PlannerInfo *root, RelOptInfo *rel,
pathnode->path.parallel_aware = false;
pathnode->path.parallel_safe = rel->consider_parallel &&
subpath->parallel_safe;
+ pathnode->path.parallel_safe_ignoring_params = rel->consider_parallel_rechecking_params &&
+ subpath->parallel_safe_ignoring_params;
pathnode->path.parallel_workers = subpath->parallel_workers;
pathnode->path.rows = subpath->rows;
pathnode->path.startup_cost = subpath->startup_cost;
diff --git a/src/backend/optimizer/util/relnode.c b/src/backend/optimizer/util/relnode.c
index 47769cea45..9d908d0fea 100644
--- a/src/backend/optimizer/util/relnode.c
+++ b/src/backend/optimizer/util/relnode.c
@@ -213,6 +213,7 @@ build_simple_rel(PlannerInfo *root, int relid, RelOptInfo *parent)
rel->consider_startup = (root->tuple_fraction > 0);
rel->consider_param_startup = false; /* might get changed later */
rel->consider_parallel = false; /* might get changed later */
+ rel->consider_parallel_rechecking_params = false; /* might get changed later */
rel->reltarget = create_empty_pathtarget();
rel->pathlist = NIL;
rel->ppilist = NIL;
@@ -617,6 +618,7 @@ build_join_rel(PlannerInfo *root,
joinrel->consider_startup = (root->tuple_fraction > 0);
joinrel->consider_param_startup = false;
joinrel->consider_parallel = false;
+ joinrel->consider_parallel_rechecking_params = false;
joinrel->reltarget = create_empty_pathtarget();
joinrel->pathlist = NIL;
joinrel->ppilist = NIL;
@@ -743,10 +745,27 @@ build_join_rel(PlannerInfo *root,
* take; therefore, we should make the same decision here however we get
* here.
*/
- if (inner_rel->consider_parallel && outer_rel->consider_parallel &&
- is_parallel_safe(root, (Node *) restrictlist) &&
- is_parallel_safe(root, (Node *) joinrel->reltarget->exprs))
- joinrel->consider_parallel = true;
+ if ((inner_rel->consider_parallel || inner_rel->consider_parallel_rechecking_params)
+ && (outer_rel->consider_parallel || outer_rel->consider_parallel_rechecking_params))
+ {
+ bool restrictlist_parallel_safe;
+ bool restrictlist_parallel_safe_ignoring_params = false;
+ bool target_parallel_safe;
+ bool target_parallel_safe_ignoring_params = false;
+
+ restrictlist_parallel_safe = is_parallel_safe(root, (Node *) restrictlist, &restrictlist_parallel_safe_ignoring_params);
+ target_parallel_safe = is_parallel_safe(root, (Node *) joinrel->reltarget->exprs, &target_parallel_safe_ignoring_params);
+
+ if (inner_rel->consider_parallel && outer_rel->consider_parallel
+ && restrictlist_parallel_safe && target_parallel_safe)
+ joinrel->consider_parallel = true;
+
+ if (inner_rel->consider_parallel_rechecking_params
+ && outer_rel->consider_parallel_rechecking_params
+ && restrictlist_parallel_safe_ignoring_params
+ && target_parallel_safe_ignoring_params)
+ joinrel->consider_parallel_rechecking_params = true;
+ }
/* Add the joinrel to the PlannerInfo. */
add_join_rel(root, joinrel);
@@ -805,6 +824,7 @@ build_child_join_rel(PlannerInfo *root, RelOptInfo *outer_rel,
joinrel->consider_startup = (root->tuple_fraction > 0);
joinrel->consider_param_startup = false;
joinrel->consider_parallel = false;
+ joinrel->consider_parallel_rechecking_params = false;
joinrel->reltarget = create_empty_pathtarget();
joinrel->pathlist = NIL;
joinrel->ppilist = NIL;
@@ -892,6 +912,7 @@ build_child_join_rel(PlannerInfo *root, RelOptInfo *outer_rel,
/* Child joinrel is parallel safe if parent is parallel safe. */
joinrel->consider_parallel = parent_joinrel->consider_parallel;
+ joinrel->consider_parallel_rechecking_params = parent_joinrel->consider_parallel_rechecking_params;
/* Set estimates of the child-joinrel's size. */
set_joinrel_size_estimates(root, joinrel, outer_rel, inner_rel,
@@ -1236,6 +1257,7 @@ fetch_upper_rel(PlannerInfo *root, UpperRelationKind kind, Relids relids)
upperrel->consider_startup = (root->tuple_fraction > 0);
upperrel->consider_param_startup = false;
upperrel->consider_parallel = false; /* might get changed later */
+ upperrel->consider_parallel_rechecking_params = false; /* might get changed later */
upperrel->reltarget = create_empty_pathtarget();
upperrel->pathlist = NIL;
upperrel->cheapest_startup_path = NULL;
diff --git a/src/backend/utils/misc/guc.c b/src/backend/utils/misc/guc.c
index 467b0fd6fe..034510b611 100644
--- a/src/backend/utils/misc/guc.c
+++ b/src/backend/utils/misc/guc.c
@@ -57,6 +57,7 @@
#include "libpq/libpq.h"
#include "libpq/pqformat.h"
#include "miscadmin.h"
+#include "optimizer/clauses.h"
#include "optimizer/cost.h"
#include "optimizer/geqo.h"
#include "optimizer/optimizer.h"
@@ -968,6 +969,16 @@ static const unit_conversion time_unit_conversion_table[] =
static struct config_bool ConfigureNamesBool[] =
{
+ {
+ {"enable_parallel_params_recheck", PGC_USERSET, QUERY_TUNING_METHOD,
+ gettext_noop("Enables the planner's rechecking of parallel safety in the presence of PARAM_EXEC params (for correlated subqueries)."),
+ NULL,
+ GUC_EXPLAIN
+ },
+ &enable_parallel_params_recheck,
+ true,
+ NULL, NULL, NULL
+ },
{
{"enable_seqscan", PGC_USERSET, QUERY_TUNING_METHOD,
gettext_noop("Enables the planner's use of sequential-scan plans."),
diff --git a/src/include/nodes/pathnodes.h b/src/include/nodes/pathnodes.h
index 1abe233db2..f2c3d229b0 100644
--- a/src/include/nodes/pathnodes.h
+++ b/src/include/nodes/pathnodes.h
@@ -683,6 +683,7 @@ typedef struct RelOptInfo
bool consider_startup; /* keep cheap-startup-cost paths? */
bool consider_param_startup; /* ditto, for parameterized paths? */
bool consider_parallel; /* consider parallel paths? */
+ bool consider_parallel_rechecking_params; /* consider parallel paths? */
/* default result targetlist for Paths scanning this relation */
struct PathTarget *reltarget; /* list of Vars/Exprs, cost, width */
@@ -1182,6 +1183,7 @@ typedef struct Path
bool parallel_aware; /* engage parallel-aware logic? */
bool parallel_safe; /* OK to use as part of parallel plan? */
+ bool parallel_safe_ignoring_params; /* OK to use as part of parallel plan if worker context provides params? */
int parallel_workers; /* desired # of workers; 0 = not parallel */
/* estimated size/costs for path (see costsize.c for more info) */
@@ -2471,7 +2473,7 @@ typedef struct MinMaxAggInfo
* for conflicting purposes.
*
* In addition, PARAM_EXEC slots are assigned for Params representing outputs
- * from subplans (values that are setParam items for those subplans). These
+ * from subplans (values that are setParam items for those subplans). [TODO: is this true, or only for init plans?] These
* IDs need not be tracked via PlannerParamItems, since we do not need any
* duplicate-elimination nor later processing of the represented expressions.
* Instead, we just record the assignment of the slot number by appending to
@@ -2590,6 +2592,7 @@ typedef struct
/* Data which may differ across partitions. */
bool target_parallel_safe;
+ bool target_parallel_safe_ignoring_params;
Node *havingQual;
List *targetList;
PartitionwiseAggregateType patype;
diff --git a/src/include/nodes/plannodes.h b/src/include/nodes/plannodes.h
index ec9a8b0c81..67805f2cfa 100644
--- a/src/include/nodes/plannodes.h
+++ b/src/include/nodes/plannodes.h
@@ -128,6 +128,7 @@ typedef struct Plan
*/
bool parallel_aware; /* engage parallel-aware logic? */
bool parallel_safe; /* OK to use as part of parallel plan? */
+ bool parallel_safe_ignoring_params; /* OK to use as part of parallel plan if worker context provides params? */
/*
* information needed for asynchronous execution
diff --git a/src/include/nodes/primnodes.h b/src/include/nodes/primnodes.h
index c04282f91f..df1e2496c7 100644
--- a/src/include/nodes/primnodes.h
+++ b/src/include/nodes/primnodes.h
@@ -764,6 +764,7 @@ typedef struct SubPlan
* spec result is UNKNOWN; this allows much
* simpler handling of null values */
bool parallel_safe; /* is the subplan parallel-safe? */
+ bool parallel_safe_ignoring_params; /* is the subplan parallel-safe when params are provided by the worker context? */
/* Note: parallel_safe does not consider contents of testexpr or args */
/* Information for passing params into and out of the subselect: */
/* setParam and parParam are lists of integers (param IDs) */
diff --git a/src/include/optimizer/clauses.h b/src/include/optimizer/clauses.h
index 0673887a85..df01be2c61 100644
--- a/src/include/optimizer/clauses.h
+++ b/src/include/optimizer/clauses.h
@@ -16,6 +16,8 @@
#include "nodes/pathnodes.h"
+extern PGDLLIMPORT bool enable_parallel_params_recheck;
+
typedef struct
{
int numWindowFuncs; /* total number of WindowFuncs found */
@@ -33,7 +35,7 @@ extern double expression_returns_set_rows(PlannerInfo *root, Node *clause);
extern bool contain_subplans(Node *clause);
extern char max_parallel_hazard(Query *parse);
-extern bool is_parallel_safe(PlannerInfo *root, Node *node);
+extern bool is_parallel_safe(PlannerInfo *root, Node *node, bool *safe_ignoring_params);
extern bool contain_nonstrict_functions(Node *clause);
extern bool contain_exec_param(Node *clause, List *param_ids);
extern bool contain_leaked_vars(Node *clause);
diff --git a/src/test/regress/expected/incremental_sort.out b/src/test/regress/expected/incremental_sort.out
index 545e301e48..8f9ca05e60 100644
--- a/src/test/regress/expected/incremental_sort.out
+++ b/src/test/regress/expected/incremental_sort.out
@@ -1614,16 +1614,16 @@ from tenk1 t, generate_series(1, 1000);
QUERY PLAN
---------------------------------------------------------------------------------
Unique
- -> Sort
- Sort Key: t.unique1, ((SubPlan 1))
- -> Gather
- Workers Planned: 2
+ -> Gather Merge
+ Workers Planned: 2
+ -> Sort
+ Sort Key: t.unique1, ((SubPlan 1))
-> Nested Loop
-> Parallel Index Only Scan using tenk1_unique1 on tenk1 t
-> Function Scan on generate_series
- SubPlan 1
- -> Index Only Scan using tenk1_unique1 on tenk1
- Index Cond: (unique1 = t.unique1)
+ SubPlan 1
+ -> Index Only Scan using tenk1_unique1 on tenk1
+ Index Cond: (unique1 = t.unique1)
(11 rows)
explain (costs off) select
@@ -1633,16 +1633,16 @@ from tenk1 t, generate_series(1, 1000)
order by 1, 2;
QUERY PLAN
---------------------------------------------------------------------------
- Sort
- Sort Key: t.unique1, ((SubPlan 1))
- -> Gather
- Workers Planned: 2
+ Gather Merge
+ Workers Planned: 2
+ -> Sort
+ Sort Key: t.unique1, ((SubPlan 1))
-> Nested Loop
-> Parallel Index Only Scan using tenk1_unique1 on tenk1 t
-> Function Scan on generate_series
- SubPlan 1
- -> Index Only Scan using tenk1_unique1 on tenk1
- Index Cond: (unique1 = t.unique1)
+ SubPlan 1
+ -> Index Only Scan using tenk1_unique1 on tenk1
+ Index Cond: (unique1 = t.unique1)
(10 rows)
-- Parallel sort but with expression not available until the upper rel.
diff --git a/src/test/regress/expected/select_parallel.out b/src/test/regress/expected/select_parallel.out
index 2303f70d6e..253f117d7a 100644
--- a/src/test/regress/expected/select_parallel.out
+++ b/src/test/regress/expected/select_parallel.out
@@ -311,6 +311,131 @@ select count(*) from tenk1 where (two, four) not in
10000
(1 row)
+-- test parallel plans for queries containing correlated subplans
+-- where the subplan only needs params available from the current
+-- worker's scan.
+explain (costs off, verbose) select
+ (select t.unique1 from tenk1 where tenk1.unique1 = t.unique1)
+ from tenk1 t, generate_series(1, 10);
+ QUERY PLAN
+----------------------------------------------------------------------------
+ Gather
+ Output: ((SubPlan 1))
+ Workers Planned: 4
+ -> Nested Loop
+ Output: (SubPlan 1)
+ -> Parallel Index Only Scan using tenk1_unique1 on public.tenk1 t
+ Output: t.unique1
+ -> Function Scan on pg_catalog.generate_series
+ Output: generate_series.generate_series
+ Function Call: generate_series(1, 10)
+ SubPlan 1
+ -> Index Only Scan using tenk1_unique1 on public.tenk1
+ Output: t.unique1
+ Index Cond: (tenk1.unique1 = t.unique1)
+(14 rows)
+
+explain (costs off, verbose) select
+ (select t.unique1 from tenk1 where tenk1.unique1 = t.unique1)
+ from tenk1 t;
+ QUERY PLAN
+----------------------------------------------------------------------
+ Gather
+ Output: ((SubPlan 1))
+ Workers Planned: 4
+ -> Parallel Index Only Scan using tenk1_unique1 on public.tenk1 t
+ Output: (SubPlan 1)
+ SubPlan 1
+ -> Index Only Scan using tenk1_unique1 on public.tenk1
+ Output: t.unique1
+ Index Cond: (tenk1.unique1 = t.unique1)
+(9 rows)
+
+explain (analyze, costs off, summary off, verbose, timing off) select
+ (select t.unique1 from tenk1 where tenk1.unique1 = t.unique1)
+ from tenk1 t
+ limit 1;
+ QUERY PLAN
+----------------------------------------------------------------------------------------------------
+ Limit (actual rows=1 loops=1)
+ Output: ((SubPlan 1))
+ -> Gather (actual rows=1 loops=1)
+ Output: ((SubPlan 1))
+ Workers Planned: 4
+ Workers Launched: 4
+ -> Parallel Index Only Scan using tenk1_unique1 on public.tenk1 t (actual rows=1 loops=5)
+ Output: (SubPlan 1)
+ Heap Fetches: 0
+ Worker 0: actual rows=1 loops=1
+ Worker 1: actual rows=1 loops=1
+ Worker 2: actual rows=1 loops=1
+ Worker 3: actual rows=1 loops=1
+ SubPlan 1
+ -> Index Only Scan using tenk1_unique1 on public.tenk1 (actual rows=1 loops=5)
+ Output: t.unique1
+ Index Cond: (tenk1.unique1 = t.unique1)
+ Heap Fetches: 0
+ Worker 0: actual rows=1 loops=1
+ Worker 1: actual rows=1 loops=1
+ Worker 2: actual rows=1 loops=1
+ Worker 3: actual rows=1 loops=1
+(22 rows)
+
+explain (costs off, verbose) select t.unique1
+ from tenk1 t
+ where t.unique1 = (select t.unique1 from tenk1 where tenk1.unique1 = t.unique1);
+ QUERY PLAN
+----------------------------------------------------------------------
+ Gather
+ Output: t.unique1
+ Workers Planned: 4
+ -> Parallel Index Only Scan using tenk1_unique1 on public.tenk1 t
+ Output: t.unique1
+ Filter: (t.unique1 = (SubPlan 1))
+ SubPlan 1
+ -> Index Only Scan using tenk1_unique1 on public.tenk1
+ Output: t.unique1
+ Index Cond: (tenk1.unique1 = t.unique1)
+(10 rows)
+
+explain (costs off, verbose) select *
+ from tenk1 t
+ order by (select t.unique1 from tenk1 where tenk1.unique1 = t.unique1);
+ QUERY PLAN
+----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
+ Gather Merge
+ Output: t.unique1, t.unique2, t.two, t.four, t.ten, t.twenty, t.hundred, t.thousand, t.twothousand, t.fivethous, t.tenthous, t.odd, t.even, t.stringu1, t.stringu2, t.string4, ((SubPlan 1))
+ Workers Planned: 4
+ -> Sort
+ Output: t.unique1, t.unique2, t.two, t.four, t.ten, t.twenty, t.hundred, t.thousand, t.twothousand, t.fivethous, t.tenthous, t.odd, t.even, t.stringu1, t.stringu2, t.string4, ((SubPlan 1))
+ Sort Key: ((SubPlan 1))
+ -> Parallel Seq Scan on public.tenk1 t
+ Output: t.unique1, t.unique2, t.two, t.four, t.ten, t.twenty, t.hundred, t.thousand, t.twothousand, t.fivethous, t.tenthous, t.odd, t.even, t.stringu1, t.stringu2, t.string4, (SubPlan 1)
+ SubPlan 1
+ -> Index Only Scan using tenk1_unique1 on public.tenk1
+ Output: t.unique1
+ Index Cond: (tenk1.unique1 = t.unique1)
+(12 rows)
+
+-- test subplan in join/lateral join
+explain (costs off, verbose, timing off) select t.unique1, l.*
+ from tenk1 t
+ join lateral (
+ select (select t.unique1 from tenk1 where tenk1.unique1 = t.unique1 offset 0)
+ ) l on true;
+ QUERY PLAN
+----------------------------------------------------------------------
+ Gather
+ Output: t.unique1, ((SubPlan 1))
+ Workers Planned: 4
+ -> Parallel Index Only Scan using tenk1_unique1 on public.tenk1 t
+ Output: t.unique1, (SubPlan 1)
+ SubPlan 1
+ -> Index Only Scan using tenk1_unique1 on public.tenk1
+ Output: t.unique1
+ Index Cond: (tenk1.unique1 = t.unique1)
+(9 rows)
+
-- this is not parallel-safe due to use of random() within SubLink's testexpr:
explain (costs off)
select * from tenk1 where (unique1 + random())::integer not in
@@ -1192,6 +1317,18 @@ EXECUTE pstmt('1', make_some_array(1,2));
DEALLOCATE pstmt;
-- test interaction between subquery and partial_paths
+-- this plan changes to using a non-parallel index only
+-- scan on tenk1_unique1 (the parallel version of the subquery scan
+-- is cheaper, but only by ~30, and cost comparison treats them as equal
+-- since the costs are so large) because set_rel_consider_parallel
+-- called from make_one_rel sees the subplan as parallel safe now
+-- (in context it now knows the params are actually parallel safe).
+-- Because of that the non-parallel index path is now parallel_safe=true,
+-- therefore it wins the COSTS_EQUAL comparison in add_path.
+-- Perhaps any is_parallel_safe calls made for the purpose of determining
+-- consider_parallel should disable that behavior? It's not clear which is
+-- correct.
+set enable_parallel_params_recheck = off;
CREATE VIEW tenk1_vw_sec WITH (security_barrier) AS SELECT * FROM tenk1;
EXPLAIN (COSTS OFF)
SELECT 1 FROM tenk1_vw_sec
diff --git a/src/test/regress/expected/sysviews.out b/src/test/regress/expected/sysviews.out
index 6e54f3e15e..e4b48fc61d 100644
--- a/src/test/regress/expected/sysviews.out
+++ b/src/test/regress/expected/sysviews.out
@@ -109,13 +109,14 @@ select name, setting from pg_settings where name like 'enable%';
enable_nestloop | on
enable_parallel_append | on
enable_parallel_hash | on
+ enable_parallel_params_recheck | on
enable_partition_pruning | on
enable_partitionwise_aggregate | off
enable_partitionwise_join | off
enable_seqscan | on
enable_sort | on
enable_tidscan | on
-(20 rows)
+(21 rows)
-- Test that the pg_timezone_names and pg_timezone_abbrevs views are
-- more-or-less working. We can't test their contents in any great detail
diff --git a/src/test/regress/sql/select_parallel.sql b/src/test/regress/sql/select_parallel.sql
index 019e17e751..f217d0ec9b 100644
--- a/src/test/regress/sql/select_parallel.sql
+++ b/src/test/regress/sql/select_parallel.sql
@@ -111,6 +111,31 @@ explain (costs off)
(select hundred, thousand from tenk2 where thousand > 100);
select count(*) from tenk1 where (two, four) not in
(select hundred, thousand from tenk2 where thousand > 100);
+-- test parallel plans for queries containing correlated subplans
+-- where the subplan only needs params available from the current
+-- worker's scan.
+explain (costs off, verbose) select
+ (select t.unique1 from tenk1 where tenk1.unique1 = t.unique1)
+ from tenk1 t, generate_series(1, 10);
+explain (costs off, verbose) select
+ (select t.unique1 from tenk1 where tenk1.unique1 = t.unique1)
+ from tenk1 t;
+explain (analyze, costs off, summary off, verbose, timing off) select
+ (select t.unique1 from tenk1 where tenk1.unique1 = t.unique1)
+ from tenk1 t
+ limit 1;
+explain (costs off, verbose) select t.unique1
+ from tenk1 t
+ where t.unique1 = (select t.unique1 from tenk1 where tenk1.unique1 = t.unique1);
+explain (costs off, verbose) select *
+ from tenk1 t
+ order by (select t.unique1 from tenk1 where tenk1.unique1 = t.unique1);
+-- test subplan in join/lateral join
+explain (costs off, verbose, timing off) select t.unique1, l.*
+ from tenk1 t
+ join lateral (
+ select (select t.unique1 from tenk1 where tenk1.unique1 = t.unique1 offset 0)
+ ) l on true;
-- this is not parallel-safe due to use of random() within SubLink's testexpr:
explain (costs off)
select * from tenk1 where (unique1 + random())::integer not in
@@ -456,6 +481,18 @@ EXECUTE pstmt('1', make_some_array(1,2));
DEALLOCATE pstmt;
-- test interaction between subquery and partial_paths
+-- this plan changes to using a non-parallel index only
+-- scan on tenk1_unique1 (the parallel version of the subquery scan
+-- is cheaper, but only by ~30, and cost comparison treats them as equal
+-- since the costs are so large) because set_rel_consider_parallel
+-- called from make_one_rel sees the subplan as parallel safe now
+-- (in context it now knows the params are actually parallel safe).
+-- Because of that the non-parallel index path is now parallel_safe=true,
+-- therefore it wins the COSTS_EQUAL comparison in add_path.
+-- Perhaps any is_parallel_safe calls made for the purpose of determining
+-- consider_parallel should disable that behavior? It's not clear which is
+-- correct.
+set enable_parallel_params_recheck = off;
CREATE VIEW tenk1_vw_sec WITH (security_barrier) AS SELECT * FROM tenk1;
EXPLAIN (COSTS OFF)
SELECT 1 FROM tenk1_vw_sec
--
2.20.1
[application/octet-stream] v3-0003-Other-places-to-consider-for-completeness.patch (5.1K, ../../CAAaqYe-mts0pTD7B3b0+0g_aUwErEiL=mhGZfj9TEGmza-jt3Q@mail.gmail.com/4-v3-0003-Other-places-to-consider-for-completeness.patch)
download | inline diff:
From c69f27574a664546d7a7e3fb3aaa98f74d8e4eba Mon Sep 17 00:00:00 2001
From: jcoleman <[email protected]>
Date: Fri, 7 May 2021 15:37:22 +0000
Subject: [PATCH v3 3/3] Other places to consider for completeness
---
src/backend/optimizer/path/allpaths.c | 4 ++++
src/backend/optimizer/plan/planmain.c | 2 +-
src/backend/optimizer/plan/planner.c | 3 +++
src/backend/optimizer/plan/subselect.c | 3 +++
src/backend/optimizer/prep/prepunion.c | 2 ++
5 files changed, 13 insertions(+), 1 deletion(-)
diff --git a/src/backend/optimizer/path/allpaths.c b/src/backend/optimizer/path/allpaths.c
index 6eb39e6a06..9849d3712a 100644
--- a/src/backend/optimizer/path/allpaths.c
+++ b/src/backend/optimizer/path/allpaths.c
@@ -1142,6 +1142,8 @@ set_append_rel_size(PlannerInfo *root, RelOptInfo *rel,
*/
if (!childrel->consider_parallel)
rel->consider_parallel = false;
+ if (!childrel->consider_parallel_rechecking_params)
+ rel->consider_parallel_rechecking_params = false;
/*
* Accumulate size information from each live child.
@@ -1263,6 +1265,8 @@ set_append_rel_pathlist(PlannerInfo *root, RelOptInfo *rel,
*/
if (!rel->consider_parallel)
childrel->consider_parallel = false;
+ if (!childrel->consider_parallel_rechecking_params)
+ rel->consider_parallel_rechecking_params = false;
/*
* Compute the child's access paths.
diff --git a/src/backend/optimizer/plan/planmain.c b/src/backend/optimizer/plan/planmain.c
index bdbce2b87d..5135f9ee97 100644
--- a/src/backend/optimizer/plan/planmain.c
+++ b/src/backend/optimizer/plan/planmain.c
@@ -119,7 +119,7 @@ query_planner(PlannerInfo *root,
if (root->glob->parallelModeOK &&
force_parallel_mode != FORCE_PARALLEL_OFF)
final_rel->consider_parallel =
- is_parallel_safe(root, parse->jointree->quals, NULL);
+ is_parallel_safe(root, parse->jointree->quals, &final_rel->consider_parallel_rechecking_params);
/*
* The only path for it is a trivial Result path. We cheat a
diff --git a/src/backend/optimizer/plan/planner.c b/src/backend/optimizer/plan/planner.c
index 008a096ee7..3d8102e9f7 100644
--- a/src/backend/optimizer/plan/planner.c
+++ b/src/backend/optimizer/plan/planner.c
@@ -4095,6 +4095,7 @@ create_window_paths(PlannerInfo *root,
if (input_rel->consider_parallel && output_target_parallel_safe &&
is_parallel_safe(root, (Node *) activeWindows, NULL))
window_rel->consider_parallel = true;
+ /* consider_parallel_rechecking_params */
/*
* If the input rel belongs to a single FDW, so does the window rel.
@@ -4292,6 +4293,7 @@ create_distinct_paths(PlannerInfo *root, RelOptInfo *input_rel)
* expressions are parallel-safe.
*/
distinct_rel->consider_parallel = input_rel->consider_parallel;
+ distinct_rel->consider_parallel_rechecking_params = input_rel->consider_parallel_rechecking_params;
/*
* If the input rel belongs to a single FDW, so does the distinct_rel.
@@ -4646,6 +4648,7 @@ create_ordered_paths(PlannerInfo *root,
*/
if (input_rel->consider_parallel && target_parallel_safe)
ordered_rel->consider_parallel = true;
+ /* consider_parallel_rechecking_params */
/*
* If the input rel belongs to a single FDW, so does the ordered_rel.
diff --git a/src/backend/optimizer/plan/subselect.c b/src/backend/optimizer/plan/subselect.c
index 393db3b42d..3e1001fa86 100644
--- a/src/backend/optimizer/plan/subselect.c
+++ b/src/backend/optimizer/plan/subselect.c
@@ -1020,6 +1020,7 @@ SS_process_ctes(PlannerInfo *root)
* parallel-safe.
*/
splan->parallel_safe = false;
+ splan->parallel_safe_ignoring_params = false;
splan->setParam = NIL;
splan->parParam = NIL;
splan->args = NIL;
@@ -2176,6 +2177,7 @@ SS_charge_for_initplans(PlannerInfo *root, RelOptInfo *final_rel)
path->startup_cost += initplan_cost;
path->total_cost += initplan_cost;
path->parallel_safe = false;
+ path->parallel_safe_ignoring_params = false;
}
/*
@@ -2184,6 +2186,7 @@ SS_charge_for_initplans(PlannerInfo *root, RelOptInfo *final_rel)
*/
final_rel->partial_pathlist = NIL;
final_rel->consider_parallel = false;
+ final_rel->consider_parallel_rechecking_params = false;
/* We needn't do set_cheapest() here, caller will do it */
}
diff --git a/src/backend/optimizer/prep/prepunion.c b/src/backend/optimizer/prep/prepunion.c
index 16cb35c914..ab92e7d7e4 100644
--- a/src/backend/optimizer/prep/prepunion.c
+++ b/src/backend/optimizer/prep/prepunion.c
@@ -273,6 +273,7 @@ recurse_set_operations(Node *setOp, PlannerInfo *root,
*/
final_rel = fetch_upper_rel(subroot, UPPERREL_FINAL, NULL);
rel->consider_parallel = final_rel->consider_parallel;
+ rel->consider_parallel_rechecking_params = final_rel->consider_parallel_rechecking_params;
/*
* For the moment, we consider only a single Path for the subquery.
@@ -617,6 +618,7 @@ generate_union_paths(SetOperationStmt *op, PlannerInfo *root,
result_rel = fetch_upper_rel(root, UPPERREL_SETOP, relids);
result_rel->reltarget = create_pathtarget(root, tlist);
result_rel->consider_parallel = consider_parallel;
+ /* consider_parallel_rechecking_params */
/*
* Append the child results together.
--
2.20.1
^ permalink raw reply [nested|flat] 35+ messages in thread
* Re: Parallelize correlated subqueries that execute within each worker
@ 2021-11-03 13:46 James Coleman <[email protected]>
parent: James Coleman <[email protected]>
0 siblings, 0 replies; 35+ messages in thread
From: James Coleman @ 2021-11-03 13:46 UTC (permalink / raw)
To: Jaime Casanova <[email protected]>; +Cc: pgsql-hackers
On Wed, Sep 8, 2021 at 8:47 AM James Coleman <[email protected]> wrote:
> See updated patch series attached.
Jaime,
I noticed on 3-October you moved this into "waiting on author"; I
don't see anything waiting in this thread, however. Am I missing
something?
I'm planning to change it back to "needs review".
Thanks,
James
^ permalink raw reply [nested|flat] 35+ messages in thread
* Re: Parallelize correlated subqueries that execute within each worker
@ 2021-11-03 14:48 Robert Haas <[email protected]>
parent: James Coleman <[email protected]>
1 sibling, 2 replies; 35+ messages in thread
From: Robert Haas @ 2021-11-03 14:48 UTC (permalink / raw)
To: James Coleman <[email protected]>; +Cc: pgsql-hackers; Amit Kapila <[email protected]>
As a preliminary comment, it would be quite useful to get Tom Lane's
opinion on this, since it's not an area I understand especially well,
and I think he understands it better than anyone.
On Fri, May 7, 2021 at 12:30 PM James Coleman <[email protected]> wrote:
> The basic idea is that we need to track (both on nodes and relations)
> not only whether that node or rel is parallel safe but also whether
> it's parallel safe assuming params are rechecked in the using context.
> That allows us to delay making a final decision until we have
> sufficient context to conclude that a given usage of a Param is
> actually parallel safe or unsafe.
I don't really understand what you mean by "assuming params are
rechecked in the using context." However, I think that a possibly
better approach to this whole area would be to try to solve the
problem by putting limits on where you can insert a Gather node.
Consider:
Nested Loop
-> Seq Scan on x
-> Index Scan on y
Index Cond: y.q = x.q
If you insert a Gather node atop the Index Scan, necessarily changing
it to a Parallel Index Scan, then you need to pass values around. For
every value we get for x.q, we would need to start workers, sending
them the value of x.q, and they do a parallel index scan working
together to find all rows where y.q = x.q, and then exit. We repeat
this for every tuple from x.q. In the absence of infrastructure to
pass those parameters, we can't put the Gather there. We also don't
want to, because it would be really slow.
If you insert the Gather node atop the Seq Scan or the Nested Loop, in
either case necessarily changing the Seq Scan to a Parallel Seq Scan,
you have no problem. If you put it on top of the Nested Loop, the
parameter will be set in the workers and used in the workers and
everything is fine. If you put it on top of the Seq Scan, the
parameter will be set in the leader -- by the Nested Loop -- and used
in the leader, and again you have no problem.
So in my view of the world, the parameter just acts as an additional
constraint on where Gather nodes can be placed. I don't see that there
are any parameters that are unsafe categorically -- they're just
unsafe if the place where they are set is on a different side of the
Gather from the place where they are used. So I don't understand --
possibly just because I'm dumb -- the idea behind
consider_parallel_rechecking_params, because that seems to be making a
sort of overall judgement about the safety or unsafety of the
parameter on its own merits, rather than thinking about the Gather
placement.
When I last worked on this, I had hoped that extParam or allParam
would be the thing that would answer the question: are there any
parameters used under this node that are not also set under this node?
But I seem to recall that neither seemed to be answering precisely
that question, and the lousy naming of those fields and limited
documentation of their intended purpose did not help.
--
Robert Haas
EDB: http://www.enterprisedb.com
^ permalink raw reply [nested|flat] 35+ messages in thread
* Re: Parallelize correlated subqueries that execute within each worker
@ 2021-11-03 15:14 Tom Lane <[email protected]>
parent: Robert Haas <[email protected]>
1 sibling, 1 reply; 35+ messages in thread
From: Tom Lane @ 2021-11-03 15:14 UTC (permalink / raw)
To: Robert Haas <[email protected]>; +Cc: James Coleman <[email protected]>; pgsql-hackers; Amit Kapila <[email protected]>
Robert Haas <[email protected]> writes:
> When I last worked on this, I had hoped that extParam or allParam
> would be the thing that would answer the question: are there any
> parameters used under this node that are not also set under this node?
> But I seem to recall that neither seemed to be answering precisely
> that question, and the lousy naming of those fields and limited
> documentation of their intended purpose did not help.
FWIW, I've never been very happy with those fields either. IIRC the
design in that area was all Vadim's, but to the extent that there's
any usable documentation of extParam/allParam, it was filled in by me
while trying to understand what Vadim did. If somebody wants to step
up and do a rewrite to make the planner's Param management more useful
or at least easier to understand, I think that'd be great.
But anyway: yeah, those fields as currently constituted don't help
much. They tell you which Params are consumed by this node or its
subnodes, but not where those Params came from. The planner's
plan_params and outer_params fields might be more nearly the right
thing, but I'm not sure they're spot-on either, nor that they're
up-to-date at the point where you'd want to make decisions about
Gather safety.
regards, tom lane
^ permalink raw reply [nested|flat] 35+ messages in thread
* Re: Parallelize correlated subqueries that execute within each worker
@ 2021-11-03 16:27 Robert Haas <[email protected]>
parent: Tom Lane <[email protected]>
0 siblings, 1 reply; 35+ messages in thread
From: Robert Haas @ 2021-11-03 16:27 UTC (permalink / raw)
To: Tom Lane <[email protected]>; +Cc: James Coleman <[email protected]>; pgsql-hackers; Amit Kapila <[email protected]>
On Wed, Nov 3, 2021 at 11:14 AM Tom Lane <[email protected]> wrote:
> FWIW, I've never been very happy with those fields either. IIRC the
> design in that area was all Vadim's, but to the extent that there's
> any usable documentation of extParam/allParam, it was filled in by me
> while trying to understand what Vadim did. If somebody wants to step
> up and do a rewrite to make the planner's Param management more useful
> or at least easier to understand, I think that'd be great.
Good to know, thanks.
> But anyway: yeah, those fields as currently constituted don't help
> much. They tell you which Params are consumed by this node or its
> subnodes, but not where those Params came from. The planner's
> plan_params and outer_params fields might be more nearly the right
> thing, but I'm not sure they're spot-on either, nor that they're
> up-to-date at the point where you'd want to make decisions about
> Gather safety.
One thing I discovered when I was looking at this a few years ago is
that there was only one query in the regression tests where extParam
and allParam were not the same. The offending query was select 1 =
all(select (select 1)), and the resulting plan has a Materialize node
with an attached InitPlan. For that Materialize node, extParam = {}
and allParam = {$0}, with $0 also being the output parameter of the
InitPlan attached that that Materialize node. In every other node in
that plan and in every node of every other plan generated by the
regression tests, the values were identical. So it's extremely niche
that these fields are even different from each other, and it's unclear
to me that we really need both of them.
What's also interesting is that extParam is computed (by
finalize_plan) as plan->extParam = bms_del_members(plan->extParam,
initSetParam). So I think it mostly ends up that extParam for a node
is not exactly all the parameters that anything under that node cares
about, but rather - approximately - all the things that anything under
that node cares about that aren't also set someplace under that node.
If it were exactly that, I think it would be perfect for our needs
here: if the set of things used but not set below the current level is
empty, it's OK to insert a Gather node; otherwise, it's not, at least,
not unless we find a way to pipe parameters from the leader into the
workers. But I think there's some reason that I no longer remember why
it's not exactly that, and therefore the idea doesn't work.
One problem I do remember is that attaching initplans at the top of
each subquery level as we presently do is really not good for this
kind of thing. Suppose you have several levels of Nested Loop and
someplace down in the plan you reference an InitPlan. The planner sees
no harm in attaching the InitPlan at the top level, which makes it
unsafe to put the Gather any place but at the top level. If you
attached the InitPlan to the lowest node in the plan tree that is high
enough to be above all the places that use the value from that
parameter, you could potentially shift the Gather down the plan tree,
which would be great if, for example, there's exactly one
parallel-restricted join and the rest are parallel-safe. The best plan
might be to do all the other joins under a Gather and then perform the
parallel-restricted join above it.
But I found it very hard to figure out how to rejigger the logic that
places InitPlans to be more intelligent, and eventually gave up.
--
Robert Haas
EDB: http://www.enterprisedb.com
^ permalink raw reply [nested|flat] 35+ messages in thread
* Re: Parallelize correlated subqueries that execute within each worker
@ 2021-11-03 16:52 Tom Lane <[email protected]>
parent: Robert Haas <[email protected]>
0 siblings, 0 replies; 35+ messages in thread
From: Tom Lane @ 2021-11-03 16:52 UTC (permalink / raw)
To: Robert Haas <[email protected]>; +Cc: James Coleman <[email protected]>; pgsql-hackers; Amit Kapila <[email protected]>
Robert Haas <[email protected]> writes:
> One thing I discovered when I was looking at this a few years ago is
> that there was only one query in the regression tests where extParam
> and allParam were not the same. The offending query was select 1 =
> all(select (select 1)), and the resulting plan has a Materialize node
> with an attached InitPlan. For that Materialize node, extParam = {}
> and allParam = {$0}, with $0 also being the output parameter of the
> InitPlan attached that that Materialize node. In every other node in
> that plan and in every node of every other plan generated by the
> regression tests, the values were identical. So it's extremely niche
> that these fields are even different from each other, and it's unclear
> to me that we really need both of them.
Yeah, I've had that nagging feeling about them too. But ISTR trying to
reduce them to one value years ago, and finding that it didn't quite work,
or at least would result in more subquery-re-evaluation than we do today.
You have to dig into what the executor uses these values for to really
grok them. I'm afraid that that detail is all swapped out right now, so
I can't say much more.
regards, tom lane
^ permalink raw reply [nested|flat] 35+ messages in thread
* Re: Parallelize correlated subqueries that execute within each worker
@ 2021-11-03 17:34 James Coleman <[email protected]>
parent: Robert Haas <[email protected]>
1 sibling, 1 reply; 35+ messages in thread
From: James Coleman @ 2021-11-03 17:34 UTC (permalink / raw)
To: Robert Haas <[email protected]>; +Cc: pgsql-hackers; Amit Kapila <[email protected]>; Tom Lane <[email protected]>
Hi Robert, thanks for the detailed reply.
On Wed, Nov 3, 2021 at 10:48 AM Robert Haas <[email protected]> wrote:
>
> As a preliminary comment, it would be quite useful to get Tom Lane's
> opinion on this, since it's not an area I understand especially well,
> and I think he understands it better than anyone.
>
> On Fri, May 7, 2021 at 12:30 PM James Coleman <[email protected]> wrote:
> > The basic idea is that we need to track (both on nodes and relations)
> > not only whether that node or rel is parallel safe but also whether
> > it's parallel safe assuming params are rechecked in the using context.
> > That allows us to delay making a final decision until we have
> > sufficient context to conclude that a given usage of a Param is
> > actually parallel safe or unsafe.
>
> I don't really understand what you mean by "assuming params are
> rechecked in the using context." However, I think that a possibly
> better approach to this whole area would be to try to solve the
> problem by putting limits on where you can insert a Gather node.
> Consider:
>
> Nested Loop
> -> Seq Scan on x
> -> Index Scan on y
> Index Cond: y.q = x.q
>
> If you insert a Gather node atop the Index Scan, necessarily changing
> it to a Parallel Index Scan, then you need to pass values around. For
> every value we get for x.q, we would need to start workers, sending
> them the value of x.q, and they do a parallel index scan working
> together to find all rows where y.q = x.q, and then exit. We repeat
> this for every tuple from x.q. In the absence of infrastructure to
> pass those parameters, we can't put the Gather there. We also don't
> want to, because it would be really slow.
>
> If you insert the Gather node atop the Seq Scan or the Nested Loop, in
> either case necessarily changing the Seq Scan to a Parallel Seq Scan,
> you have no problem. If you put it on top of the Nested Loop, the
> parameter will be set in the workers and used in the workers and
> everything is fine. If you put it on top of the Seq Scan, the
> parameter will be set in the leader -- by the Nested Loop -- and used
> in the leader, and again you have no problem.
>
> So in my view of the world, the parameter just acts as an additional
> constraint on where Gather nodes can be placed. I don't see that there
> are any parameters that are unsafe categorically -- they're just
> unsafe if the place where they are set is on a different side of the
> Gather from the place where they are used. So I don't understand --
> possibly just because I'm dumb -- the idea behind
> consider_parallel_rechecking_params, because that seems to be making a
> sort of overall judgement about the safety or unsafety of the
> parameter on its own merits, rather than thinking about the Gather
> placement.
I had to read through this several times before I understood the point
(not your fault, this is, as you note, a complicated area). I *think*
if I grok it properly you're effectively describing what this patch
results in conceptually (but possibly solving it from a different
direction).
As I understand the current code, parallel plans are largely chosen
based not on where it's safe to insert a Gather node but rather by
determining if a given path is parallel safe. Through that lens params
are a bit of an odd man out -- they aren't inherently unsafe in the
way a parallel-unsafe function is, but they can only be used in
parallel plans under certain conditions (whether because of project
policy, performance, or missing infrastructure).
Under that paradigm the existing consider_parallel and parallel_safe
boolean values imply everything is about whether a plan is inherently
parallel safe. Thus the current doesn't have the context to handle the
nuance of params (as they are not inherently parallel-safe or unsafe).
Introducing consider_parallel_rechecking_params and
parallel_safe_ignoring_params allows us to keep more context on params
and make a more nuanced decision at the proper level of the plan. This
is what I mean by "rechecked in the using context", though I realize
now that both "recheck" and "context" are overloaded terms in the
project, so don't describe the concept particularly clearly. When a
path relies on params we can only make a final determination about its
parallel safety if we know whether or not the current parallel node
can provide the param's value. We don't necessarily know that
information until we attempt to generate a full parallel node in the
plan (I think what you're describing as "inserting a Gather node")
since the param may come from another node in the plan. These new
values allow us to do that by tracking tentatively parallel-safe
subplans (given proper Gather node placement) and delaying the
parallel-safety determination until the point at which a param is
available (or not).
Is that a more helpful framing of what my goal is here?
> When I last worked on this, I had hoped that extParam or allParam
> would be the thing that would answer the question: are there any
> parameters used under this node that are not also set under this node?
> But I seem to recall that neither seemed to be answering precisely
> that question, and the lousy naming of those fields and limited
> documentation of their intended purpose did not help.
I don't really know anything about extParam or allParam, so I can't
offer any insight here.
Thanks,
James Coleman
^ permalink raw reply [nested|flat] 35+ messages in thread
* Re: Parallelize correlated subqueries that execute within each worker
@ 2021-11-15 15:01 Robert Haas <[email protected]>
parent: James Coleman <[email protected]>
0 siblings, 3 replies; 35+ messages in thread
From: Robert Haas @ 2021-11-15 15:01 UTC (permalink / raw)
To: James Coleman <[email protected]>; +Cc: pgsql-hackers; Amit Kapila <[email protected]>; Tom Lane <[email protected]>
On Wed, Nov 3, 2021 at 1:34 PM James Coleman <[email protected]> wrote:
> As I understand the current code, parallel plans are largely chosen
> based not on where it's safe to insert a Gather node but rather by
> determining if a given path is parallel safe. Through that lens params
> are a bit of an odd man out -- they aren't inherently unsafe in the
> way a parallel-unsafe function is, but they can only be used in
> parallel plans under certain conditions (whether because of project
> policy, performance, or missing infrastructure).
Right.
> Introducing consider_parallel_rechecking_params and
> parallel_safe_ignoring_params allows us to keep more context on params
> and make a more nuanced decision at the proper level of the plan. This
> is what I mean by "rechecked in the using context", though I realize
> now that both "recheck" and "context" are overloaded terms in the
> project, so don't describe the concept particularly clearly. When a
> path relies on params we can only make a final determination about its
> parallel safety if we know whether or not the current parallel node
> can provide the param's value. We don't necessarily know that
> information until we attempt to generate a full parallel node in the
> plan (I think what you're describing as "inserting a Gather node")
> since the param may come from another node in the plan. These new
> values allow us to do that by tracking tentatively parallel-safe
> subplans (given proper Gather node placement) and delaying the
> parallel-safety determination until the point at which a param is
> available (or not).
So I think I agree with you here. But I don't like all of this
"ignoring_params" stuff and I don't see why it's necessary. Say we
don't have both parallel_safe and parallel_safe_ignoring_params. Say
we just have parallel_safe. If the plan will be parallel safe if the
params are available, we label it parallel safe. If the plan will not
be parallel safe even if the params are available, we say it's not
parallel safe. Then, when we get to generate_gather_paths(), we don't
generate any paths if there are required parameters that are not
available. What's wrong with that approach?
Maybe it's clearer to say this: I feel like one extra Boolean is
either too much or too little. I think maybe it's not even needed. But
if it is needed, then why just a bool instead of, say, a Bitmapset of
params that are needed, or something?
I'm sort of speaking from intuition here rather than sure knowledge. I
might be totally wrong.
--
Robert Haas
EDB: http://www.enterprisedb.com
^ permalink raw reply [nested|flat] 35+ messages in thread
* Re: Parallelize correlated subqueries that execute within each worker
@ 2021-12-03 07:35 Michael Paquier <[email protected]>
parent: Robert Haas <[email protected]>
2 siblings, 0 replies; 35+ messages in thread
From: Michael Paquier @ 2021-12-03 07:35 UTC (permalink / raw)
To: Robert Haas <[email protected]>; +Cc: James Coleman <[email protected]>; pgsql-hackers; Amit Kapila <[email protected]>; Tom Lane <[email protected]>
On Mon, Nov 15, 2021 at 10:01:37AM -0500, Robert Haas wrote:
> On Wed, Nov 3, 2021 at 1:34 PM James Coleman <[email protected]> wrote:
>> As I understand the current code, parallel plans are largely chosen
>> based not on where it's safe to insert a Gather node but rather by
>> determining if a given path is parallel safe. Through that lens params
>> are a bit of an odd man out -- they aren't inherently unsafe in the
>> way a parallel-unsafe function is, but they can only be used in
>> parallel plans under certain conditions (whether because of project
>> policy, performance, or missing infrastructure).
>
> Right.
Please note that the CF bot is complaining here, so I have moved this
patch to the next CF, but changed the status as waiting on author.
--
Michael
Attachments:
[application/pgp-signature] signature.asc (833B, ../../[email protected]/2-signature.asc)
download
^ permalink raw reply [nested|flat] 35+ messages in thread
* Re: Parallelize correlated subqueries that execute within each worker
@ 2022-08-02 20:57 Jacob Champion <[email protected]>
parent: Robert Haas <[email protected]>
2 siblings, 0 replies; 35+ messages in thread
From: Jacob Champion @ 2022-08-02 20:57 UTC (permalink / raw)
To: Andres Freund <[email protected]>; James Coleman <[email protected]>; +Cc: Robert Haas <[email protected]>; pgsql-hackers; Amit Kapila <[email protected]>; Tom Lane <[email protected]>
This entry has been waiting on author input for a while (our current
threshold is roughly two weeks), so I've marked it Returned with
Feedback.
Once you think the patchset is ready for review again, you (or any
interested party) can resurrect the patch entry by visiting
https://commitfest.postgresql.org/38/3246/
and changing the status to "Needs Review", and then changing the
status again to "Move to next CF". (Don't forget the second step;
hopefully we will have streamlined this in the near future!)
Thanks,
--Jacob
^ permalink raw reply [nested|flat] 35+ messages in thread
* Re: Parallelize correlated subqueries that execute within each worker
@ 2022-09-27 02:56 James Coleman <[email protected]>
parent: Robert Haas <[email protected]>
2 siblings, 2 replies; 35+ messages in thread
From: James Coleman @ 2022-09-27 02:56 UTC (permalink / raw)
To: Andres Freund <[email protected]>; +Cc: Robert Haas <[email protected]>; pgsql-hackers; Amit Kapila <[email protected]>; Tom Lane <[email protected]>
On Mon, Mar 21, 2022 at 8:48 PM Andres Freund <[email protected]> wrote:
>
> Hi,
>
> On 2022-01-22 20:25:19 -0500, James Coleman wrote:
> > On the other hand this is a dramatically simpler patch series.
> > Assuming the approach is sound, it should much easier to maintain than
> > the previous version.
> >
> > The final patch in the series is a set of additional checks I could
> > imagine to try to be more explicit, but at least in the current test
> > suite there isn't anything at all they affect.
> >
> > Does this look at least somewhat more like what you'd envisionsed
> > (granting the need to squint hard given the relids checks instead of
> > directly checking params)?
>
> This fails on freebsd (so likely a timing issue): https://cirrus-ci.com/task/4758411492458496?logs=test_world#L2225
>
> Marked as waiting on author.
I've finally gotten around to checking this out, and the issue was an
"explain analyze" test that had actual loops different on FreeBSD.
There doesn't seem to be a way to disable loop output, but instead of
processing the explain output with e.g. a function (as we do some
other places) to remove the offending and unnecessary output I've just
removed the "analyze" (as I don't believe it was actually necessary).
Attached is an updated patch series. In this version I've removed the
"parallelize some subqueries with limit" patch since discussion is
proceeding in the spun off thread. The first patch adds additional
tests so that you can see how those new tests change with the code
changes in the 2nd patch in the series. As before the final patch in
the series includes changes where we may also want to verify
correctness but don't have a test demonstrating the need.
Thanks,
James Coleman
Attachments:
[application/octet-stream] v5-0002-Parallelize-correlated-subqueries.patch (25.2K, ../../CAAaqYe9hJ=GzcaVSH82e8o6edr3bkYkauhk_yLiGVbF=8xss1w@mail.gmail.com/2-v5-0002-Parallelize-correlated-subqueries.patch)
download | inline diff:
From 07ccd5b8d1776b5109c54d20ed3dcaef22d752f9 Mon Sep 17 00:00:00 2001
From: jcoleman <[email protected]>
Date: Fri, 21 Jan 2022 22:38:46 -0500
Subject: [PATCH v5 2/3] Parallelize correlated subqueries
When params are provided at the current query level (i.e., are generated
within a single worker and not shared across workers) we can safely
execute these in parallel.
Alternative approach using just relids subset check
---
doc/src/sgml/parallel.sgml | 3 +-
src/backend/optimizer/path/allpaths.c | 18 ++-
src/backend/optimizer/path/joinpath.c | 16 ++-
src/backend/optimizer/util/clauses.c | 3 +
src/backend/optimizer/util/pathnode.c | 2 +
src/include/nodes/pathnodes.h | 2 +-
.../regress/expected/incremental_sort.out | 28 ++--
src/test/regress/expected/partition_prune.out | 104 +++++++-------
src/test/regress/expected/select_parallel.out | 128 ++++++++++--------
9 files changed, 169 insertions(+), 135 deletions(-)
diff --git a/doc/src/sgml/parallel.sgml b/doc/src/sgml/parallel.sgml
index c37fb67065..d44325dd89 100644
--- a/doc/src/sgml/parallel.sgml
+++ b/doc/src/sgml/parallel.sgml
@@ -517,7 +517,8 @@ EXPLAIN SELECT * FROM pgbench_accounts WHERE filler LIKE '%x%';
<listitem>
<para>
- Plan nodes that reference a correlated <literal>SubPlan</literal>.
+ Plan nodes that reference a correlated <literal>SubPlan</literal> where
+ the result is shared between workers.
</para>
</listitem>
</itemizedlist>
diff --git a/src/backend/optimizer/path/allpaths.c b/src/backend/optimizer/path/allpaths.c
index 8fc28007f5..e1ad9ae372 100644
--- a/src/backend/optimizer/path/allpaths.c
+++ b/src/backend/optimizer/path/allpaths.c
@@ -558,7 +558,8 @@ set_rel_pathlist(PlannerInfo *root, RelOptInfo *rel,
* the final scan/join targetlist is available (see grouping_planner).
*/
if (rel->reloptkind == RELOPT_BASEREL &&
- !bms_equal(rel->relids, root->all_baserels))
+ !bms_equal(rel->relids, root->all_baserels)
+ && (rel->subplan_params == NIL || rte->rtekind != RTE_SUBQUERY))
generate_useful_gather_paths(root, rel, false);
/* Now find the cheapest of the paths for this rel */
@@ -3025,7 +3026,7 @@ generate_gather_paths(PlannerInfo *root, RelOptInfo *rel, bool override_rows)
cheapest_partial_path->rows * cheapest_partial_path->parallel_workers;
simple_gather_path = (Path *)
create_gather_path(root, rel, cheapest_partial_path, rel->reltarget,
- NULL, rowsp);
+ rel->lateral_relids, rowsp);
add_path(rel, simple_gather_path);
/*
@@ -3042,7 +3043,7 @@ generate_gather_paths(PlannerInfo *root, RelOptInfo *rel, bool override_rows)
rows = subpath->rows * subpath->parallel_workers;
path = create_gather_merge_path(root, rel, subpath, rel->reltarget,
- subpath->pathkeys, NULL, rowsp);
+ subpath->pathkeys, rel->lateral_relids, rowsp);
add_path(rel, &path->path);
}
}
@@ -3144,11 +3145,15 @@ generate_useful_gather_paths(PlannerInfo *root, RelOptInfo *rel, bool override_r
double *rowsp = NULL;
List *useful_pathkeys_list = NIL;
Path *cheapest_partial_path = NULL;
+ Relids required_outer = rel->lateral_relids;
/* If there are no partial paths, there's nothing to do here. */
if (rel->partial_pathlist == NIL)
return;
+ if (!bms_is_subset(required_outer, rel->relids))
+ return;
+
/* Should we override the rel's rowcount estimate? */
if (override_rows)
rowsp = &rows;
@@ -3220,7 +3225,7 @@ generate_useful_gather_paths(PlannerInfo *root, RelOptInfo *rel, bool override_r
tmp,
rel->reltarget,
tmp->pathkeys,
- NULL,
+ required_outer,
rowsp);
add_path(rel, &path->path);
@@ -3254,7 +3259,7 @@ generate_useful_gather_paths(PlannerInfo *root, RelOptInfo *rel, bool override_r
tmp,
rel->reltarget,
tmp->pathkeys,
- NULL,
+ required_outer,
rowsp);
add_path(rel, &path->path);
@@ -3433,7 +3438,8 @@ standard_join_search(PlannerInfo *root, int levels_needed, List *initial_rels)
/*
* Except for the topmost scan/join rel, consider gathering
* partial paths. We'll do the same for the topmost scan/join rel
- * once we know the final targetlist (see grouping_planner).
+ * once we know the final targetlist (see
+ * apply_scanjoin_target_to_paths).
*/
if (!bms_equal(rel->relids, root->all_baserels))
generate_useful_gather_paths(root, rel, false);
diff --git a/src/backend/optimizer/path/joinpath.c b/src/backend/optimizer/path/joinpath.c
index 2a3f0ab7bf..21606f6e59 100644
--- a/src/backend/optimizer/path/joinpath.c
+++ b/src/backend/optimizer/path/joinpath.c
@@ -1791,16 +1791,24 @@ match_unsorted_outer(PlannerInfo *root,
* partial path and the joinrel is parallel-safe. However, we can't
* handle JOIN_UNIQUE_OUTER, because the outer path will be partial, and
* therefore we won't be able to properly guarantee uniqueness. Nor can
- * we handle joins needing lateral rels, since partial paths must not be
- * parameterized. Similarly, we can't handle JOIN_FULL and JOIN_RIGHT,
- * because they can produce false null extended rows.
+ * we handle JOIN_FULL and JOIN_RIGHT, because they can produce false null
+ * extended rows.
+ *
+ * Partial paths may only have parameters in limited cases
+ * where the parameterization is fully satisfied without sharing state
+ * between workers, so we only allow lateral rels on inputs to the join
+ * if the resulting join contains no lateral rels, the inner rel's laterals
+ * are fully satisfied by the outer rel, and the outer rel doesn't depend
+ * on the inner rel to produce any laterals.
*/
if (joinrel->consider_parallel &&
save_jointype != JOIN_UNIQUE_OUTER &&
save_jointype != JOIN_FULL &&
save_jointype != JOIN_RIGHT &&
outerrel->partial_pathlist != NIL &&
- bms_is_empty(joinrel->lateral_relids))
+ bms_is_empty(joinrel->lateral_relids) &&
+ bms_is_subset(innerrel->lateral_relids, outerrel->relids) &&
+ (bms_is_empty(outerrel->lateral_relids) || !bms_is_subset(outerrel->lateral_relids, innerrel->relids)))
{
if (nestjoinOK)
consider_parallel_nestloop(root, joinrel, outerrel, innerrel,
diff --git a/src/backend/optimizer/util/clauses.c b/src/backend/optimizer/util/clauses.c
index bf3a7cae60..11bab7fa7e 100644
--- a/src/backend/optimizer/util/clauses.c
+++ b/src/backend/optimizer/util/clauses.c
@@ -822,6 +822,9 @@ max_parallel_hazard_walker(Node *node, max_parallel_hazard_context *context)
if (param->paramkind == PARAM_EXTERN)
return false;
+ if (param->paramkind == PARAM_EXEC)
+ return false;
+
if (param->paramkind != PARAM_EXEC ||
!list_member_int(context->safe_param_ids, param->paramid))
{
diff --git a/src/backend/optimizer/util/pathnode.c b/src/backend/optimizer/util/pathnode.c
index e10561d843..e8309342f0 100644
--- a/src/backend/optimizer/util/pathnode.c
+++ b/src/backend/optimizer/util/pathnode.c
@@ -2437,6 +2437,8 @@ create_nestloop_path(PlannerInfo *root,
NestPath *pathnode = makeNode(NestPath);
Relids inner_req_outer = PATH_REQ_OUTER(inner_path);
+ /* TODO: Assert lateral relids subset safety? */
+
/*
* If the inner path is parameterized by the outer, we must drop any
* restrict_clauses that are due to be moved into the inner path. We have
diff --git a/src/include/nodes/pathnodes.h b/src/include/nodes/pathnodes.h
index 294cfe9c47..b69d4e2692 100644
--- a/src/include/nodes/pathnodes.h
+++ b/src/include/nodes/pathnodes.h
@@ -2964,7 +2964,7 @@ typedef struct MinMaxAggInfo
* for conflicting purposes.
*
* In addition, PARAM_EXEC slots are assigned for Params representing outputs
- * from subplans (values that are setParam items for those subplans). These
+ * from subplans (values that are setParam items for those subplans). [TODO: is this true, or only for init plans?] These
* IDs need not be tracked via PlannerParamItems, since we do not need any
* duplicate-elimination nor later processing of the represented expressions.
* Instead, we just record the assignment of the slot number by appending to
diff --git a/src/test/regress/expected/incremental_sort.out b/src/test/regress/expected/incremental_sort.out
index 49953eaade..66c09381f1 100644
--- a/src/test/regress/expected/incremental_sort.out
+++ b/src/test/regress/expected/incremental_sort.out
@@ -1612,16 +1612,16 @@ from tenk1 t, generate_series(1, 1000);
QUERY PLAN
---------------------------------------------------------------------------------
Unique
- -> Sort
- Sort Key: t.unique1, ((SubPlan 1))
- -> Gather
- Workers Planned: 2
+ -> Gather Merge
+ Workers Planned: 2
+ -> Sort
+ Sort Key: t.unique1, ((SubPlan 1))
-> Nested Loop
-> Parallel Index Only Scan using tenk1_unique1 on tenk1 t
-> Function Scan on generate_series
- SubPlan 1
- -> Index Only Scan using tenk1_unique1 on tenk1
- Index Cond: (unique1 = t.unique1)
+ SubPlan 1
+ -> Index Only Scan using tenk1_unique1 on tenk1
+ Index Cond: (unique1 = t.unique1)
(11 rows)
explain (costs off) select
@@ -1631,16 +1631,16 @@ from tenk1 t, generate_series(1, 1000)
order by 1, 2;
QUERY PLAN
---------------------------------------------------------------------------
- Sort
- Sort Key: t.unique1, ((SubPlan 1))
- -> Gather
- Workers Planned: 2
+ Gather Merge
+ Workers Planned: 2
+ -> Sort
+ Sort Key: t.unique1, ((SubPlan 1))
-> Nested Loop
-> Parallel Index Only Scan using tenk1_unique1 on tenk1 t
-> Function Scan on generate_series
- SubPlan 1
- -> Index Only Scan using tenk1_unique1 on tenk1
- Index Cond: (unique1 = t.unique1)
+ SubPlan 1
+ -> Index Only Scan using tenk1_unique1 on tenk1
+ Index Cond: (unique1 = t.unique1)
(10 rows)
-- Parallel sort but with expression not available until the upper rel.
diff --git a/src/test/regress/expected/partition_prune.out b/src/test/regress/expected/partition_prune.out
index 7555764c77..5c45f9c0a5 100644
--- a/src/test/regress/expected/partition_prune.out
+++ b/src/test/regress/expected/partition_prune.out
@@ -1284,60 +1284,64 @@ EXPLAIN (VERBOSE, COSTS OFF) SELECT * FROM part p(x) ORDER BY x;
--
-- pruning won't work for mc3p, because some keys are Params
explain (costs off) select * from mc2p t1, lateral (select count(*) from mc3p t2 where t2.a = t1.b and abs(t2.b) = 1 and t2.c = 1) s where t1.a = 1;
- QUERY PLAN
------------------------------------------------------------------------
- Nested Loop
- -> Append
- -> Seq Scan on mc2p1 t1_1
- Filter: (a = 1)
- -> Seq Scan on mc2p2 t1_2
- Filter: (a = 1)
- -> Seq Scan on mc2p_default t1_3
- Filter: (a = 1)
- -> Aggregate
- -> Append
- -> Seq Scan on mc3p0 t2_1
- Filter: ((a = t1.b) AND (c = 1) AND (abs(b) = 1))
- -> Seq Scan on mc3p1 t2_2
- Filter: ((a = t1.b) AND (c = 1) AND (abs(b) = 1))
- -> Seq Scan on mc3p2 t2_3
- Filter: ((a = t1.b) AND (c = 1) AND (abs(b) = 1))
- -> Seq Scan on mc3p3 t2_4
- Filter: ((a = t1.b) AND (c = 1) AND (abs(b) = 1))
- -> Seq Scan on mc3p4 t2_5
- Filter: ((a = t1.b) AND (c = 1) AND (abs(b) = 1))
- -> Seq Scan on mc3p5 t2_6
- Filter: ((a = t1.b) AND (c = 1) AND (abs(b) = 1))
- -> Seq Scan on mc3p6 t2_7
- Filter: ((a = t1.b) AND (c = 1) AND (abs(b) = 1))
- -> Seq Scan on mc3p7 t2_8
- Filter: ((a = t1.b) AND (c = 1) AND (abs(b) = 1))
- -> Seq Scan on mc3p_default t2_9
- Filter: ((a = t1.b) AND (c = 1) AND (abs(b) = 1))
-(28 rows)
+ QUERY PLAN
+-----------------------------------------------------------------------------
+ Gather
+ Workers Planned: 2
+ -> Nested Loop
+ -> Parallel Append
+ -> Parallel Seq Scan on mc2p1 t1_1
+ Filter: (a = 1)
+ -> Parallel Seq Scan on mc2p2 t1_2
+ Filter: (a = 1)
+ -> Parallel Seq Scan on mc2p_default t1_3
+ Filter: (a = 1)
+ -> Aggregate
+ -> Append
+ -> Seq Scan on mc3p0 t2_1
+ Filter: ((a = t1.b) AND (c = 1) AND (abs(b) = 1))
+ -> Seq Scan on mc3p1 t2_2
+ Filter: ((a = t1.b) AND (c = 1) AND (abs(b) = 1))
+ -> Seq Scan on mc3p2 t2_3
+ Filter: ((a = t1.b) AND (c = 1) AND (abs(b) = 1))
+ -> Seq Scan on mc3p3 t2_4
+ Filter: ((a = t1.b) AND (c = 1) AND (abs(b) = 1))
+ -> Seq Scan on mc3p4 t2_5
+ Filter: ((a = t1.b) AND (c = 1) AND (abs(b) = 1))
+ -> Seq Scan on mc3p5 t2_6
+ Filter: ((a = t1.b) AND (c = 1) AND (abs(b) = 1))
+ -> Seq Scan on mc3p6 t2_7
+ Filter: ((a = t1.b) AND (c = 1) AND (abs(b) = 1))
+ -> Seq Scan on mc3p7 t2_8
+ Filter: ((a = t1.b) AND (c = 1) AND (abs(b) = 1))
+ -> Seq Scan on mc3p_default t2_9
+ Filter: ((a = t1.b) AND (c = 1) AND (abs(b) = 1))
+(30 rows)
-- pruning should work fine, because values for a prefix of keys (a, b) are
-- available
explain (costs off) select * from mc2p t1, lateral (select count(*) from mc3p t2 where t2.c = t1.b and abs(t2.b) = 1 and t2.a = 1) s where t1.a = 1;
- QUERY PLAN
------------------------------------------------------------------------
- Nested Loop
- -> Append
- -> Seq Scan on mc2p1 t1_1
- Filter: (a = 1)
- -> Seq Scan on mc2p2 t1_2
- Filter: (a = 1)
- -> Seq Scan on mc2p_default t1_3
- Filter: (a = 1)
- -> Aggregate
- -> Append
- -> Seq Scan on mc3p0 t2_1
- Filter: ((c = t1.b) AND (a = 1) AND (abs(b) = 1))
- -> Seq Scan on mc3p1 t2_2
- Filter: ((c = t1.b) AND (a = 1) AND (abs(b) = 1))
- -> Seq Scan on mc3p_default t2_3
- Filter: ((c = t1.b) AND (a = 1) AND (abs(b) = 1))
-(16 rows)
+ QUERY PLAN
+-----------------------------------------------------------------------------
+ Gather
+ Workers Planned: 2
+ -> Nested Loop
+ -> Parallel Append
+ -> Parallel Seq Scan on mc2p1 t1_1
+ Filter: (a = 1)
+ -> Parallel Seq Scan on mc2p2 t1_2
+ Filter: (a = 1)
+ -> Parallel Seq Scan on mc2p_default t1_3
+ Filter: (a = 1)
+ -> Aggregate
+ -> Append
+ -> Seq Scan on mc3p0 t2_1
+ Filter: ((c = t1.b) AND (a = 1) AND (abs(b) = 1))
+ -> Seq Scan on mc3p1 t2_2
+ Filter: ((c = t1.b) AND (a = 1) AND (abs(b) = 1))
+ -> Seq Scan on mc3p_default t2_3
+ Filter: ((c = t1.b) AND (a = 1) AND (abs(b) = 1))
+(18 rows)
-- also here, because values for all keys are provided
explain (costs off) select * from mc2p t1, lateral (select count(*) from mc3p t2 where t2.a = 1 and abs(t2.b) = 1 and t2.c = 1) s where t1.a = 1;
diff --git a/src/test/regress/expected/select_parallel.out b/src/test/regress/expected/select_parallel.out
index 9b4d7dd44a..01443e2ffb 100644
--- a/src/test/regress/expected/select_parallel.out
+++ b/src/test/regress/expected/select_parallel.out
@@ -137,8 +137,8 @@ create table part_pa_test_p2 partition of part_pa_test for values from (0) to (m
explain (costs off)
select (select max((select pa1.b from part_pa_test pa1 where pa1.a = pa2.a)))
from part_pa_test pa2;
- QUERY PLAN
---------------------------------------------------------------
+ QUERY PLAN
+----------------------------------------------------------------
Aggregate
-> Gather
Workers Planned: 3
@@ -148,12 +148,14 @@ explain (costs off)
SubPlan 2
-> Result
SubPlan 1
- -> Append
- -> Seq Scan on part_pa_test_p1 pa1_1
- Filter: (a = pa2.a)
- -> Seq Scan on part_pa_test_p2 pa1_2
- Filter: (a = pa2.a)
-(14 rows)
+ -> Gather
+ Workers Planned: 3
+ -> Parallel Append
+ -> Parallel Seq Scan on part_pa_test_p1 pa1_1
+ Filter: (a = pa2.a)
+ -> Parallel Seq Scan on part_pa_test_p2 pa1_2
+ Filter: (a = pa2.a)
+(16 rows)
drop table part_pa_test;
-- test with leader participation disabled
@@ -320,19 +322,19 @@ explain (costs off, verbose) select
QUERY PLAN
----------------------------------------------------------------------------
Gather
- Output: (SubPlan 1)
+ Output: ((SubPlan 1))
Workers Planned: 4
-> Nested Loop
- Output: t.unique1
+ Output: (SubPlan 1)
-> Parallel Index Only Scan using tenk1_unique1 on public.tenk1 t
Output: t.unique1
-> Function Scan on pg_catalog.generate_series
Output: generate_series.generate_series
Function Call: generate_series(1, 10)
- SubPlan 1
- -> Index Only Scan using tenk1_unique1 on public.tenk1
- Output: t.unique1
- Index Cond: (tenk1.unique1 = t.unique1)
+ SubPlan 1
+ -> Index Only Scan using tenk1_unique1 on public.tenk1
+ Output: t.unique1
+ Index Cond: (tenk1.unique1 = t.unique1)
(14 rows)
explain (costs off, verbose) select
@@ -341,63 +343,69 @@ explain (costs off, verbose) select
QUERY PLAN
----------------------------------------------------------------------
Gather
- Output: (SubPlan 1)
+ Output: ((SubPlan 1))
Workers Planned: 4
-> Parallel Index Only Scan using tenk1_unique1 on public.tenk1 t
- Output: t.unique1
- SubPlan 1
- -> Index Only Scan using tenk1_unique1 on public.tenk1
- Output: t.unique1
- Index Cond: (tenk1.unique1 = t.unique1)
+ Output: (SubPlan 1)
+ SubPlan 1
+ -> Index Only Scan using tenk1_unique1 on public.tenk1
+ Output: t.unique1
+ Index Cond: (tenk1.unique1 = t.unique1)
(9 rows)
explain (costs off, verbose) select
(select t.unique1 from tenk1 where tenk1.unique1 = t.unique1)
from tenk1 t
limit 1;
- QUERY PLAN
--------------------------------------------------------------------
+ QUERY PLAN
+----------------------------------------------------------------------------
Limit
Output: ((SubPlan 1))
- -> Seq Scan on public.tenk1 t
- Output: (SubPlan 1)
- SubPlan 1
- -> Index Only Scan using tenk1_unique1 on public.tenk1
- Output: t.unique1
- Index Cond: (tenk1.unique1 = t.unique1)
-(8 rows)
+ -> Gather
+ Output: ((SubPlan 1))
+ Workers Planned: 4
+ -> Parallel Index Only Scan using tenk1_unique1 on public.tenk1 t
+ Output: (SubPlan 1)
+ SubPlan 1
+ -> Index Only Scan using tenk1_unique1 on public.tenk1
+ Output: t.unique1
+ Index Cond: (tenk1.unique1 = t.unique1)
+(11 rows)
explain (costs off, verbose) select t.unique1
from tenk1 t
where t.unique1 = (select t.unique1 from tenk1 where tenk1.unique1 = t.unique1);
- QUERY PLAN
--------------------------------------------------------------
- Seq Scan on public.tenk1 t
+ QUERY PLAN
+----------------------------------------------------------------------
+ Gather
Output: t.unique1
- Filter: (t.unique1 = (SubPlan 1))
- SubPlan 1
- -> Index Only Scan using tenk1_unique1 on public.tenk1
- Output: t.unique1
- Index Cond: (tenk1.unique1 = t.unique1)
-(7 rows)
+ Workers Planned: 4
+ -> Parallel Index Only Scan using tenk1_unique1 on public.tenk1 t
+ Output: t.unique1
+ Filter: (t.unique1 = (SubPlan 1))
+ SubPlan 1
+ -> Index Only Scan using tenk1_unique1 on public.tenk1
+ Output: t.unique1
+ Index Cond: (tenk1.unique1 = t.unique1)
+(10 rows)
explain (costs off, verbose) select *
from tenk1 t
order by (select t.unique1 from tenk1 where tenk1.unique1 = t.unique1);
- QUERY PLAN
-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
- Sort
+ QUERY PLAN
+----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
+ Gather Merge
Output: t.unique1, t.unique2, t.two, t.four, t.ten, t.twenty, t.hundred, t.thousand, t.twothousand, t.fivethous, t.tenthous, t.odd, t.even, t.stringu1, t.stringu2, t.string4, ((SubPlan 1))
- Sort Key: ((SubPlan 1))
- -> Gather
- Output: t.unique1, t.unique2, t.two, t.four, t.ten, t.twenty, t.hundred, t.thousand, t.twothousand, t.fivethous, t.tenthous, t.odd, t.even, t.stringu1, t.stringu2, t.string4, (SubPlan 1)
- Workers Planned: 4
+ Workers Planned: 4
+ -> Sort
+ Output: t.unique1, t.unique2, t.two, t.four, t.ten, t.twenty, t.hundred, t.thousand, t.twothousand, t.fivethous, t.tenthous, t.odd, t.even, t.stringu1, t.stringu2, t.string4, ((SubPlan 1))
+ Sort Key: ((SubPlan 1))
-> Parallel Seq Scan on public.tenk1 t
- Output: t.unique1, t.unique2, t.two, t.four, t.ten, t.twenty, t.hundred, t.thousand, t.twothousand, t.fivethous, t.tenthous, t.odd, t.even, t.stringu1, t.stringu2, t.string4
- SubPlan 1
- -> Index Only Scan using tenk1_unique1 on public.tenk1
- Output: t.unique1
- Index Cond: (tenk1.unique1 = t.unique1)
+ Output: t.unique1, t.unique2, t.two, t.four, t.ten, t.twenty, t.hundred, t.thousand, t.twothousand, t.fivethous, t.tenthous, t.odd, t.even, t.stringu1, t.stringu2, t.string4, (SubPlan 1)
+ SubPlan 1
+ -> Index Only Scan using tenk1_unique1 on public.tenk1
+ Output: t.unique1
+ Index Cond: (tenk1.unique1 = t.unique1)
(12 rows)
-- test subplan in join/lateral join
@@ -409,14 +417,14 @@ explain (costs off, verbose, timing off) select t.unique1, l.*
QUERY PLAN
----------------------------------------------------------------------
Gather
- Output: t.unique1, (SubPlan 1)
+ Output: t.unique1, ((SubPlan 1))
Workers Planned: 4
-> Parallel Index Only Scan using tenk1_unique1 on public.tenk1 t
- Output: t.unique1
- SubPlan 1
- -> Index Only Scan using tenk1_unique1 on public.tenk1
- Output: t.unique1
- Index Cond: (tenk1.unique1 = t.unique1)
+ Output: t.unique1, (SubPlan 1)
+ SubPlan 1
+ -> Index Only Scan using tenk1_unique1 on public.tenk1
+ Output: t.unique1
+ Index Cond: (tenk1.unique1 = t.unique1)
(9 rows)
-- this is not parallel-safe due to use of random() within SubLink's testexpr:
@@ -1322,8 +1330,10 @@ SELECT 1 FROM tenk1_vw_sec
-> Parallel Index Only Scan using tenk1_unique1 on tenk1
SubPlan 1
-> Aggregate
- -> Seq Scan on int4_tbl
- Filter: (f1 < tenk1_vw_sec.unique1)
-(9 rows)
+ -> Gather
+ Workers Planned: 1
+ -> Parallel Seq Scan on int4_tbl
+ Filter: (f1 < tenk1_vw_sec.unique1)
+(11 rows)
rollback;
--
2.32.1 (Apple Git-133)
[application/octet-stream] v5-0003-Possible-additional-checks.patch (3.2K, ../../CAAaqYe9hJ=GzcaVSH82e8o6edr3bkYkauhk_yLiGVbF=8xss1w@mail.gmail.com/3-v5-0003-Possible-additional-checks.patch)
download | inline diff:
From bb794cf9b4fd6cd33e01ea8aa89e863fffade13f Mon Sep 17 00:00:00 2001
From: jcoleman <[email protected]>
Date: Sat, 22 Jan 2022 17:33:23 -0500
Subject: [PATCH v5 3/3] Possible additional checks
---
src/backend/optimizer/path/allpaths.c | 33 ++++++++++++++++++++++-----
1 file changed, 27 insertions(+), 6 deletions(-)
diff --git a/src/backend/optimizer/path/allpaths.c b/src/backend/optimizer/path/allpaths.c
index e1ad9ae372..e19cbbe90f 100644
--- a/src/backend/optimizer/path/allpaths.c
+++ b/src/backend/optimizer/path/allpaths.c
@@ -3007,11 +3007,16 @@ generate_gather_paths(PlannerInfo *root, RelOptInfo *rel, bool override_rows)
ListCell *lc;
double rows;
double *rowsp = NULL;
+ Relids required_outer = rel->lateral_relids;
/* If there are no partial paths, there's nothing to do here. */
if (rel->partial_pathlist == NIL)
return;
+ if (!bms_is_subset(required_outer, rel->relids))
+ return;
+
+
/* Should we override the rel's rowcount estimate? */
if (override_rows)
rowsp = &rows;
@@ -3022,12 +3027,16 @@ generate_gather_paths(PlannerInfo *root, RelOptInfo *rel, bool override_rows)
* of partial_pathlist because of the way add_partial_path works.
*/
cheapest_partial_path = linitial(rel->partial_pathlist);
- rows =
- cheapest_partial_path->rows * cheapest_partial_path->parallel_workers;
- simple_gather_path = (Path *)
- create_gather_path(root, rel, cheapest_partial_path, rel->reltarget,
- rel->lateral_relids, rowsp);
- add_path(rel, simple_gather_path);
+ if (cheapest_partial_path->param_info == NULL ||
+ bms_is_subset(cheapest_partial_path->param_info->ppi_req_outer, rel->relids))
+ {
+ rows =
+ cheapest_partial_path->rows * cheapest_partial_path->parallel_workers;
+ simple_gather_path = (Path *)
+ create_gather_path(root, rel, cheapest_partial_path, rel->reltarget,
+ rel->lateral_relids, rowsp);
+ add_path(rel, simple_gather_path);
+ }
/*
* For each useful ordering, we can consider an order-preserving Gather
@@ -3041,6 +3050,10 @@ generate_gather_paths(PlannerInfo *root, RelOptInfo *rel, bool override_rows)
if (subpath->pathkeys == NIL)
continue;
+ if (subpath->param_info != NULL &&
+ !bms_is_subset(subpath->param_info->ppi_req_outer, rel->relids))
+ break;
+
rows = subpath->rows * subpath->parallel_workers;
path = create_gather_merge_path(root, rel, subpath, rel->reltarget,
subpath->pathkeys, rel->lateral_relids, rowsp);
@@ -3213,6 +3226,10 @@ generate_useful_gather_paths(PlannerInfo *root, RelOptInfo *rel, bool override_r
{
Path *tmp;
+ if (subpath->param_info != NULL &&
+ !bms_is_subset(subpath->param_info->ppi_req_outer, rel->relids))
+ break;
+
tmp = (Path *) create_sort_path(root,
rel,
subpath,
@@ -3241,6 +3258,10 @@ generate_useful_gather_paths(PlannerInfo *root, RelOptInfo *rel, bool override_r
{
Path *tmp;
+ if (subpath->param_info != NULL &&
+ !bms_is_subset(subpath->param_info->ppi_req_outer, rel->relids))
+ break;
+
/*
* We should have already excluded pathkeys of length 1
* because then presorted_keys > 0 would imply is_sorted was
--
2.32.1 (Apple Git-133)
[application/octet-stream] v5-0001-Add-tests-before-change.patch (7.2K, ../../CAAaqYe9hJ=GzcaVSH82e8o6edr3bkYkauhk_yLiGVbF=8xss1w@mail.gmail.com/4-v5-0001-Add-tests-before-change.patch)
download | inline diff:
From edc5bb3c0ba9d1aaa5d85e9716ce84856ad40514 Mon Sep 17 00:00:00 2001
From: jcoleman <[email protected]>
Date: Mon, 26 Sep 2022 20:30:23 -0400
Subject: [PATCH v5 1/3] Add tests before change
---
src/test/regress/expected/select_parallel.out | 108 ++++++++++++++++++
src/test/regress/sql/select_parallel.sql | 25 ++++
2 files changed, 133 insertions(+)
diff --git a/src/test/regress/expected/select_parallel.out b/src/test/regress/expected/select_parallel.out
index 91f74fe47a..9b4d7dd44a 100644
--- a/src/test/regress/expected/select_parallel.out
+++ b/src/test/regress/expected/select_parallel.out
@@ -311,6 +311,114 @@ select count(*) from tenk1 where (two, four) not in
10000
(1 row)
+-- test parallel plans for queries containing correlated subplans
+-- where the subplan only needs params available from the current
+-- worker's scan.
+explain (costs off, verbose) select
+ (select t.unique1 from tenk1 where tenk1.unique1 = t.unique1)
+ from tenk1 t, generate_series(1, 10);
+ QUERY PLAN
+----------------------------------------------------------------------------
+ Gather
+ Output: (SubPlan 1)
+ Workers Planned: 4
+ -> Nested Loop
+ Output: t.unique1
+ -> Parallel Index Only Scan using tenk1_unique1 on public.tenk1 t
+ Output: t.unique1
+ -> Function Scan on pg_catalog.generate_series
+ Output: generate_series.generate_series
+ Function Call: generate_series(1, 10)
+ SubPlan 1
+ -> Index Only Scan using tenk1_unique1 on public.tenk1
+ Output: t.unique1
+ Index Cond: (tenk1.unique1 = t.unique1)
+(14 rows)
+
+explain (costs off, verbose) select
+ (select t.unique1 from tenk1 where tenk1.unique1 = t.unique1)
+ from tenk1 t;
+ QUERY PLAN
+----------------------------------------------------------------------
+ Gather
+ Output: (SubPlan 1)
+ Workers Planned: 4
+ -> Parallel Index Only Scan using tenk1_unique1 on public.tenk1 t
+ Output: t.unique1
+ SubPlan 1
+ -> Index Only Scan using tenk1_unique1 on public.tenk1
+ Output: t.unique1
+ Index Cond: (tenk1.unique1 = t.unique1)
+(9 rows)
+
+explain (costs off, verbose) select
+ (select t.unique1 from tenk1 where tenk1.unique1 = t.unique1)
+ from tenk1 t
+ limit 1;
+ QUERY PLAN
+-------------------------------------------------------------------
+ Limit
+ Output: ((SubPlan 1))
+ -> Seq Scan on public.tenk1 t
+ Output: (SubPlan 1)
+ SubPlan 1
+ -> Index Only Scan using tenk1_unique1 on public.tenk1
+ Output: t.unique1
+ Index Cond: (tenk1.unique1 = t.unique1)
+(8 rows)
+
+explain (costs off, verbose) select t.unique1
+ from tenk1 t
+ where t.unique1 = (select t.unique1 from tenk1 where tenk1.unique1 = t.unique1);
+ QUERY PLAN
+-------------------------------------------------------------
+ Seq Scan on public.tenk1 t
+ Output: t.unique1
+ Filter: (t.unique1 = (SubPlan 1))
+ SubPlan 1
+ -> Index Only Scan using tenk1_unique1 on public.tenk1
+ Output: t.unique1
+ Index Cond: (tenk1.unique1 = t.unique1)
+(7 rows)
+
+explain (costs off, verbose) select *
+ from tenk1 t
+ order by (select t.unique1 from tenk1 where tenk1.unique1 = t.unique1);
+ QUERY PLAN
+----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
+ Sort
+ Output: t.unique1, t.unique2, t.two, t.four, t.ten, t.twenty, t.hundred, t.thousand, t.twothousand, t.fivethous, t.tenthous, t.odd, t.even, t.stringu1, t.stringu2, t.string4, ((SubPlan 1))
+ Sort Key: ((SubPlan 1))
+ -> Gather
+ Output: t.unique1, t.unique2, t.two, t.four, t.ten, t.twenty, t.hundred, t.thousand, t.twothousand, t.fivethous, t.tenthous, t.odd, t.even, t.stringu1, t.stringu2, t.string4, (SubPlan 1)
+ Workers Planned: 4
+ -> Parallel Seq Scan on public.tenk1 t
+ Output: t.unique1, t.unique2, t.two, t.four, t.ten, t.twenty, t.hundred, t.thousand, t.twothousand, t.fivethous, t.tenthous, t.odd, t.even, t.stringu1, t.stringu2, t.string4
+ SubPlan 1
+ -> Index Only Scan using tenk1_unique1 on public.tenk1
+ Output: t.unique1
+ Index Cond: (tenk1.unique1 = t.unique1)
+(12 rows)
+
+-- test subplan in join/lateral join
+explain (costs off, verbose, timing off) select t.unique1, l.*
+ from tenk1 t
+ join lateral (
+ select (select t.unique1 from tenk1 where tenk1.unique1 = t.unique1 offset 0)
+ ) l on true;
+ QUERY PLAN
+----------------------------------------------------------------------
+ Gather
+ Output: t.unique1, (SubPlan 1)
+ Workers Planned: 4
+ -> Parallel Index Only Scan using tenk1_unique1 on public.tenk1 t
+ Output: t.unique1
+ SubPlan 1
+ -> Index Only Scan using tenk1_unique1 on public.tenk1
+ Output: t.unique1
+ Index Cond: (tenk1.unique1 = t.unique1)
+(9 rows)
+
-- this is not parallel-safe due to use of random() within SubLink's testexpr:
explain (costs off)
select * from tenk1 where (unique1 + random())::integer not in
diff --git a/src/test/regress/sql/select_parallel.sql b/src/test/regress/sql/select_parallel.sql
index 62fb68c7a0..21c2f1c742 100644
--- a/src/test/regress/sql/select_parallel.sql
+++ b/src/test/regress/sql/select_parallel.sql
@@ -111,6 +111,31 @@ explain (costs off)
(select hundred, thousand from tenk2 where thousand > 100);
select count(*) from tenk1 where (two, four) not in
(select hundred, thousand from tenk2 where thousand > 100);
+-- test parallel plans for queries containing correlated subplans
+-- where the subplan only needs params available from the current
+-- worker's scan.
+explain (costs off, verbose) select
+ (select t.unique1 from tenk1 where tenk1.unique1 = t.unique1)
+ from tenk1 t, generate_series(1, 10);
+explain (costs off, verbose) select
+ (select t.unique1 from tenk1 where tenk1.unique1 = t.unique1)
+ from tenk1 t;
+explain (costs off, verbose) select
+ (select t.unique1 from tenk1 where tenk1.unique1 = t.unique1)
+ from tenk1 t
+ limit 1;
+explain (costs off, verbose) select t.unique1
+ from tenk1 t
+ where t.unique1 = (select t.unique1 from tenk1 where tenk1.unique1 = t.unique1);
+explain (costs off, verbose) select *
+ from tenk1 t
+ order by (select t.unique1 from tenk1 where tenk1.unique1 = t.unique1);
+-- test subplan in join/lateral join
+explain (costs off, verbose, timing off) select t.unique1, l.*
+ from tenk1 t
+ join lateral (
+ select (select t.unique1 from tenk1 where tenk1.unique1 = t.unique1 offset 0)
+ ) l on true;
-- this is not parallel-safe due to use of random() within SubLink's testexpr:
explain (costs off)
select * from tenk1 where (unique1 + random())::integer not in
--
2.32.1 (Apple Git-133)
^ permalink raw reply [nested|flat] 35+ messages in thread
* Re: Parallelize correlated subqueries that execute within each worker
@ 2023-01-23 14:00 James Coleman <[email protected]>
parent: James Coleman <[email protected]>
1 sibling, 2 replies; 35+ messages in thread
From: James Coleman @ 2023-01-23 14:00 UTC (permalink / raw)
To: Tomas Vondra <[email protected]>; +Cc: vignesh C <[email protected]>; Andres Freund <[email protected]>; Robert Haas <[email protected]>; pgsql-hackers; Amit Kapila <[email protected]>; Tom Lane <[email protected]>
On Sat, Jan 21, 2023 at 10:07 PM James Coleman <[email protected]> wrote:
> ...
> While working through Tomas's comment about a conditional in the
> max_parallel_hazard_waker being guaranteed true I realized that in the
> current version of the patch the safe_param_ids tracking in
> is_parallel_safe isn't actually needed any longer. That seemed
> suspicious, and so I started digging, and I found out that in the
> current approach all of the tests pass with only the changes in
> clauses.c. I don't believe that the other changes aren't needed;
> rather I believe there isn't yet a test case exercising them, but I
> realize that means I can't prove they're needed. I spent some time
> poking at this, but at least with my current level of imagination I
> haven't stumbled across a query that would exercise these checks.
I played with this a good bit more yesterday, I'm now a good bit more
confident this is correct. I've cleaned up the patch; see attached for
v7.
Here's some of my thought process:
The comments in src/include/nodes/pathnodes.h:2953 tell us that
PARAM_EXEC params are used to pass values around from one plan node to
another in the following ways:
1. Values down into subqueries (for outer references in subqueries)
2. Up out of subqueries (for the results of a subplan)
3. From a NestLoop plan node into its inner relation (when the inner
scan is parameterized with values from the outer relation)
Case (2) is already known to be safe (we currently add these params to
safe_param_ids in max_parallel_hazard_walker when we encounter a
SubPlan node).
I also believe case (3) is already handled. We don't build partial
paths for joins when joinrel->lateral_relids is non-empty, and join
order calculations already require that parameterization here go the
correct way (i.e., inner depends on outer rather than the other way
around).
That leaves us with only case (1) to consider in this patch. Another
way of saying this is that this is really the only thing the
safe_param_ids tracking is guarding against. For params passed down
into subqueries we can further distinguish between init plans and
"regular" subplans. We already know that params from init plans are
safe (at the right level). So we're concerned here with a way to know
if the params passed to subplans are safe. We already track required
rels in ParamPathInfo, so it's fairly simple to do this test.
Which this patch we do in fact now see (as expected) rels with
non-empty lateral_relids showing up in generate_[useful_]gather_paths.
And the partial paths can now have non-empty required outer rels. I'm
not able to come up with a plan that would actually be caught by those
checks; I theorize that because of the few places we actually call
generate_[useful_]gather_paths we are in practice already excluding
those, but for now I've left these as a conditional rather than an
assertion because it seems like the kind of guard we'd want to ensure
those methods are safe.
The other other place that we actually create gather[_merge] paths is
gather_grouping_paths(), and there I've chosen to use assertions,
because the point at which grouping happens in planning suggests to me
that we shouldn't have lateral dependencies at that point. If someone
is concerned about that, I'd be happy to change those to conditionals
also.
James Coleman
Attachments:
[application/octet-stream] v8-0001-Add-tests-before-change.patch (7.2K, ../../CAAaqYe9V+2TTwGDUu12NLu1tDf0SnwvYnTOrKz=uTh6cLx3McA@mail.gmail.com/2-v8-0001-Add-tests-before-change.patch)
download | inline diff:
From d7a74b2f26edaf36d5098b4b45e19c437a4ebbdf Mon Sep 17 00:00:00 2001
From: jcoleman <[email protected]>
Date: Mon, 26 Sep 2022 20:30:23 -0400
Subject: [PATCH v8 1/2] Add tests before change
---
src/test/regress/expected/select_parallel.out | 108 ++++++++++++++++++
src/test/regress/sql/select_parallel.sql | 25 ++++
2 files changed, 133 insertions(+)
diff --git a/src/test/regress/expected/select_parallel.out b/src/test/regress/expected/select_parallel.out
index 91f74fe47a..9b4d7dd44a 100644
--- a/src/test/regress/expected/select_parallel.out
+++ b/src/test/regress/expected/select_parallel.out
@@ -311,6 +311,114 @@ select count(*) from tenk1 where (two, four) not in
10000
(1 row)
+-- test parallel plans for queries containing correlated subplans
+-- where the subplan only needs params available from the current
+-- worker's scan.
+explain (costs off, verbose) select
+ (select t.unique1 from tenk1 where tenk1.unique1 = t.unique1)
+ from tenk1 t, generate_series(1, 10);
+ QUERY PLAN
+----------------------------------------------------------------------------
+ Gather
+ Output: (SubPlan 1)
+ Workers Planned: 4
+ -> Nested Loop
+ Output: t.unique1
+ -> Parallel Index Only Scan using tenk1_unique1 on public.tenk1 t
+ Output: t.unique1
+ -> Function Scan on pg_catalog.generate_series
+ Output: generate_series.generate_series
+ Function Call: generate_series(1, 10)
+ SubPlan 1
+ -> Index Only Scan using tenk1_unique1 on public.tenk1
+ Output: t.unique1
+ Index Cond: (tenk1.unique1 = t.unique1)
+(14 rows)
+
+explain (costs off, verbose) select
+ (select t.unique1 from tenk1 where tenk1.unique1 = t.unique1)
+ from tenk1 t;
+ QUERY PLAN
+----------------------------------------------------------------------
+ Gather
+ Output: (SubPlan 1)
+ Workers Planned: 4
+ -> Parallel Index Only Scan using tenk1_unique1 on public.tenk1 t
+ Output: t.unique1
+ SubPlan 1
+ -> Index Only Scan using tenk1_unique1 on public.tenk1
+ Output: t.unique1
+ Index Cond: (tenk1.unique1 = t.unique1)
+(9 rows)
+
+explain (costs off, verbose) select
+ (select t.unique1 from tenk1 where tenk1.unique1 = t.unique1)
+ from tenk1 t
+ limit 1;
+ QUERY PLAN
+-------------------------------------------------------------------
+ Limit
+ Output: ((SubPlan 1))
+ -> Seq Scan on public.tenk1 t
+ Output: (SubPlan 1)
+ SubPlan 1
+ -> Index Only Scan using tenk1_unique1 on public.tenk1
+ Output: t.unique1
+ Index Cond: (tenk1.unique1 = t.unique1)
+(8 rows)
+
+explain (costs off, verbose) select t.unique1
+ from tenk1 t
+ where t.unique1 = (select t.unique1 from tenk1 where tenk1.unique1 = t.unique1);
+ QUERY PLAN
+-------------------------------------------------------------
+ Seq Scan on public.tenk1 t
+ Output: t.unique1
+ Filter: (t.unique1 = (SubPlan 1))
+ SubPlan 1
+ -> Index Only Scan using tenk1_unique1 on public.tenk1
+ Output: t.unique1
+ Index Cond: (tenk1.unique1 = t.unique1)
+(7 rows)
+
+explain (costs off, verbose) select *
+ from tenk1 t
+ order by (select t.unique1 from tenk1 where tenk1.unique1 = t.unique1);
+ QUERY PLAN
+----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
+ Sort
+ Output: t.unique1, t.unique2, t.two, t.four, t.ten, t.twenty, t.hundred, t.thousand, t.twothousand, t.fivethous, t.tenthous, t.odd, t.even, t.stringu1, t.stringu2, t.string4, ((SubPlan 1))
+ Sort Key: ((SubPlan 1))
+ -> Gather
+ Output: t.unique1, t.unique2, t.two, t.four, t.ten, t.twenty, t.hundred, t.thousand, t.twothousand, t.fivethous, t.tenthous, t.odd, t.even, t.stringu1, t.stringu2, t.string4, (SubPlan 1)
+ Workers Planned: 4
+ -> Parallel Seq Scan on public.tenk1 t
+ Output: t.unique1, t.unique2, t.two, t.four, t.ten, t.twenty, t.hundred, t.thousand, t.twothousand, t.fivethous, t.tenthous, t.odd, t.even, t.stringu1, t.stringu2, t.string4
+ SubPlan 1
+ -> Index Only Scan using tenk1_unique1 on public.tenk1
+ Output: t.unique1
+ Index Cond: (tenk1.unique1 = t.unique1)
+(12 rows)
+
+-- test subplan in join/lateral join
+explain (costs off, verbose, timing off) select t.unique1, l.*
+ from tenk1 t
+ join lateral (
+ select (select t.unique1 from tenk1 where tenk1.unique1 = t.unique1 offset 0)
+ ) l on true;
+ QUERY PLAN
+----------------------------------------------------------------------
+ Gather
+ Output: t.unique1, (SubPlan 1)
+ Workers Planned: 4
+ -> Parallel Index Only Scan using tenk1_unique1 on public.tenk1 t
+ Output: t.unique1
+ SubPlan 1
+ -> Index Only Scan using tenk1_unique1 on public.tenk1
+ Output: t.unique1
+ Index Cond: (tenk1.unique1 = t.unique1)
+(9 rows)
+
-- this is not parallel-safe due to use of random() within SubLink's testexpr:
explain (costs off)
select * from tenk1 where (unique1 + random())::integer not in
diff --git a/src/test/regress/sql/select_parallel.sql b/src/test/regress/sql/select_parallel.sql
index 62fb68c7a0..21c2f1c742 100644
--- a/src/test/regress/sql/select_parallel.sql
+++ b/src/test/regress/sql/select_parallel.sql
@@ -111,6 +111,31 @@ explain (costs off)
(select hundred, thousand from tenk2 where thousand > 100);
select count(*) from tenk1 where (two, four) not in
(select hundred, thousand from tenk2 where thousand > 100);
+-- test parallel plans for queries containing correlated subplans
+-- where the subplan only needs params available from the current
+-- worker's scan.
+explain (costs off, verbose) select
+ (select t.unique1 from tenk1 where tenk1.unique1 = t.unique1)
+ from tenk1 t, generate_series(1, 10);
+explain (costs off, verbose) select
+ (select t.unique1 from tenk1 where tenk1.unique1 = t.unique1)
+ from tenk1 t;
+explain (costs off, verbose) select
+ (select t.unique1 from tenk1 where tenk1.unique1 = t.unique1)
+ from tenk1 t
+ limit 1;
+explain (costs off, verbose) select t.unique1
+ from tenk1 t
+ where t.unique1 = (select t.unique1 from tenk1 where tenk1.unique1 = t.unique1);
+explain (costs off, verbose) select *
+ from tenk1 t
+ order by (select t.unique1 from tenk1 where tenk1.unique1 = t.unique1);
+-- test subplan in join/lateral join
+explain (costs off, verbose, timing off) select t.unique1, l.*
+ from tenk1 t
+ join lateral (
+ select (select t.unique1 from tenk1 where tenk1.unique1 = t.unique1 offset 0)
+ ) l on true;
-- this is not parallel-safe due to use of random() within SubLink's testexpr:
explain (costs off)
select * from tenk1 where (unique1 + random())::integer not in
--
2.32.1 (Apple Git-133)
[application/octet-stream] v8-0002-Parallelize-correlated-subqueries.patch (30.4K, ../../CAAaqYe9V+2TTwGDUu12NLu1tDf0SnwvYnTOrKz=uTh6cLx3McA@mail.gmail.com/3-v8-0002-Parallelize-correlated-subqueries.patch)
download | inline diff:
From 3ddb8ea8ba949965b01cf8fd741f84d60f891945 Mon Sep 17 00:00:00 2001
From: jcoleman <[email protected]>
Date: Wed, 18 Jan 2023 20:43:26 -0500
Subject: [PATCH v8 2/2] Parallelize correlated subqueries
When params are provided at the current query level (i.e., are generated
within a single worker and not shared across workers) we can safely
execute these in parallel.
Alternative approach using just relids subset check
---
doc/src/sgml/parallel.sgml | 3 +-
src/backend/optimizer/path/allpaths.c | 45 ++++--
src/backend/optimizer/path/joinpath.c | 10 +-
src/backend/optimizer/plan/planner.c | 8 ++
src/backend/optimizer/util/clauses.c | 74 ++++------
.../regress/expected/incremental_sort.out | 41 +++---
src/test/regress/expected/partition_prune.out | 104 +++++++-------
src/test/regress/expected/select_parallel.out | 128 ++++++++++--------
8 files changed, 221 insertions(+), 192 deletions(-)
diff --git a/doc/src/sgml/parallel.sgml b/doc/src/sgml/parallel.sgml
index 5acc9537d6..fd32572ec8 100644
--- a/doc/src/sgml/parallel.sgml
+++ b/doc/src/sgml/parallel.sgml
@@ -518,7 +518,8 @@ EXPLAIN SELECT * FROM pgbench_accounts WHERE filler LIKE '%x%';
<listitem>
<para>
- Plan nodes that reference a correlated <literal>SubPlan</literal>.
+ Plan nodes that reference a correlated <literal>SubPlan</literal> where
+ the result is shared between workers.
</para>
</listitem>
</itemizedlist>
diff --git a/src/backend/optimizer/path/allpaths.c b/src/backend/optimizer/path/allpaths.c
index c2fc568dc8..0ff94690c3 100644
--- a/src/backend/optimizer/path/allpaths.c
+++ b/src/backend/optimizer/path/allpaths.c
@@ -3018,11 +3018,19 @@ generate_gather_paths(PlannerInfo *root, RelOptInfo *rel, bool override_rows)
ListCell *lc;
double rows;
double *rowsp = NULL;
+ Relids required_outer = rel->lateral_relids;
/* If there are no partial paths, there's nothing to do here. */
if (rel->partial_pathlist == NIL)
return;
+ /*
+ * Delay gather path creation until the level in the join tree where all
+ * params used in a worker are generated within that worker.
+ */
+ if (!bms_is_subset(required_outer, rel->relids))
+ return;
+
/* Should we override the rel's rowcount estimate? */
if (override_rows)
rowsp = &rows;
@@ -3033,12 +3041,17 @@ generate_gather_paths(PlannerInfo *root, RelOptInfo *rel, bool override_rows)
* of partial_pathlist because of the way add_partial_path works.
*/
cheapest_partial_path = linitial(rel->partial_pathlist);
- rows =
- cheapest_partial_path->rows * cheapest_partial_path->parallel_workers;
- simple_gather_path = (Path *)
- create_gather_path(root, rel, cheapest_partial_path, rel->reltarget,
- NULL, rowsp);
- add_path(rel, simple_gather_path);
+
+ /* We can't pass params to workers. */
+ if (bms_is_subset(PATH_REQ_OUTER(cheapest_partial_path), rel->relids))
+ {
+ rows =
+ cheapest_partial_path->rows * cheapest_partial_path->parallel_workers;
+ simple_gather_path = (Path *)
+ create_gather_path(root, rel, cheapest_partial_path, rel->reltarget,
+ required_outer, rowsp);
+ add_path(rel, simple_gather_path);
+ }
/*
* For each useful ordering, we can consider an order-preserving Gather
@@ -3052,9 +3065,13 @@ generate_gather_paths(PlannerInfo *root, RelOptInfo *rel, bool override_rows)
if (subpath->pathkeys == NIL)
continue;
+ /* We can't pass params to workers. */
+ if (!bms_is_subset(PATH_REQ_OUTER(subpath), rel->relids))
+ continue;
+
rows = subpath->rows * subpath->parallel_workers;
path = create_gather_merge_path(root, rel, subpath, rel->reltarget,
- subpath->pathkeys, NULL, rowsp);
+ subpath->pathkeys, required_outer, rowsp);
add_path(rel, &path->path);
}
}
@@ -3156,11 +3173,19 @@ generate_useful_gather_paths(PlannerInfo *root, RelOptInfo *rel, bool override_r
double *rowsp = NULL;
List *useful_pathkeys_list = NIL;
Path *cheapest_partial_path = NULL;
+ Relids required_outer = rel->lateral_relids;
/* If there are no partial paths, there's nothing to do here. */
if (rel->partial_pathlist == NIL)
return;
+ /*
+ * Delay gather path creation until the level in the join tree where all
+ * params used in a worker are generated within that worker.
+ */
+ if (!bms_is_subset(required_outer, rel->relids))
+ return;
+
/* Should we override the rel's rowcount estimate? */
if (override_rows)
rowsp = &rows;
@@ -3217,6 +3242,10 @@ generate_useful_gather_paths(PlannerInfo *root, RelOptInfo *rel, bool override_r
(presorted_keys == 0 || !enable_incremental_sort))
continue;
+ /* We can't pass params to workers. */
+ if (!bms_is_subset(PATH_REQ_OUTER(subpath), rel->relids))
+ continue;
+
/*
* Consider regular sort for any path that's not presorted or if
* incremental sort is disabled. We've no need to consider both
@@ -3249,7 +3278,7 @@ generate_useful_gather_paths(PlannerInfo *root, RelOptInfo *rel, bool override_r
subpath,
rel->reltarget,
subpath->pathkeys,
- NULL,
+ required_outer,
rowsp);
add_path(rel, &path->path);
diff --git a/src/backend/optimizer/path/joinpath.c b/src/backend/optimizer/path/joinpath.c
index d345c0437a..644b90ad1e 100644
--- a/src/backend/optimizer/path/joinpath.c
+++ b/src/backend/optimizer/path/joinpath.c
@@ -1791,10 +1791,12 @@ match_unsorted_outer(PlannerInfo *root,
* Consider partial nestloop and mergejoin plan if outerrel has any
* partial path and the joinrel is parallel-safe. However, we can't
* handle JOIN_UNIQUE_OUTER, because the outer path will be partial, and
- * therefore we won't be able to properly guarantee uniqueness. Nor can
- * we handle joins needing lateral rels, since partial paths must not be
- * parameterized. Similarly, we can't handle JOIN_FULL and JOIN_RIGHT,
- * because they can produce false null extended rows.
+ * therefore we won't be able to properly guarantee uniqueness. Similarly,
+ * we can't handle JOIN_FULL and JOIN_RIGHT, because they can produce false
+ * null extended rows.
+ *
+ * While partial paths may now be parameterized so long as all of the params
+ * can be generated wholly within a worker we punt on supporting that here.
*/
if (joinrel->consider_parallel &&
save_jointype != JOIN_UNIQUE_OUTER &&
diff --git a/src/backend/optimizer/plan/planner.c b/src/backend/optimizer/plan/planner.c
index 05f44faf6e..fcde41d9f3 100644
--- a/src/backend/optimizer/plan/planner.c
+++ b/src/backend/optimizer/plan/planner.c
@@ -7344,11 +7344,16 @@ gather_grouping_paths(PlannerInfo *root, RelOptInfo *rel)
ListCell *lc;
Path *cheapest_partial_path;
+ /* By grouping time we shouldn't have any lateral dependencies. */
+ Assert(rel->lateral_relids == NULL);
+
/* Try Gather for unordered paths and Gather Merge for ordered ones. */
generate_useful_gather_paths(root, rel, true);
/* Try cheapest partial path + explicit Sort + Gather Merge. */
cheapest_partial_path = linitial(rel->partial_pathlist);
+ /* By grouping time we shouldn't have any lateral dependencies. */
+ Assert(PATH_REQ_OUTER(cheapest_partial_path) == NULL);
if (!pathkeys_contained_in(root->group_pathkeys,
cheapest_partial_path->pathkeys))
{
@@ -7400,6 +7405,9 @@ gather_grouping_paths(PlannerInfo *root, RelOptInfo *rel)
if (presorted_keys == 0)
continue;
+ /* By grouping time we shouldn't have any lateral dependencies. */
+ Assert(PATH_REQ_OUTER(path) == NULL);
+
path = (Path *) create_incremental_sort_path(root,
rel,
path,
diff --git a/src/backend/optimizer/util/clauses.c b/src/backend/optimizer/util/clauses.c
index aa584848cf..4a3a0489a8 100644
--- a/src/backend/optimizer/util/clauses.c
+++ b/src/backend/optimizer/util/clauses.c
@@ -89,7 +89,6 @@ typedef struct
{
char max_hazard; /* worst proparallel hazard found so far */
char max_interesting; /* worst proparallel hazard of interest */
- List *safe_param_ids; /* PARAM_EXEC Param IDs to treat as safe */
} max_parallel_hazard_context;
static bool contain_agg_clause_walker(Node *node, void *context);
@@ -618,7 +617,6 @@ max_parallel_hazard(Query *parse)
context.max_hazard = PROPARALLEL_SAFE;
context.max_interesting = PROPARALLEL_UNSAFE;
- context.safe_param_ids = NIL;
(void) max_parallel_hazard_walker((Node *) parse, &context);
return context.max_hazard;
}
@@ -629,43 +627,24 @@ max_parallel_hazard(Query *parse)
*
* root->glob->maxParallelHazard must previously have been set to the
* result of max_parallel_hazard() on the whole query.
+ *
+ * The caller is responsible for verifying that PARAM_EXEC Params are generated
+ * at the current plan level.
*/
bool
is_parallel_safe(PlannerInfo *root, Node *node)
{
max_parallel_hazard_context context;
- PlannerInfo *proot;
- ListCell *l;
/*
- * Even if the original querytree contained nothing unsafe, we need to
- * search the expression if we have generated any PARAM_EXEC Params while
- * planning, because those are parallel-restricted and there might be one
- * in this expression. But otherwise we don't need to look.
+ * If we've already checked the querytree don't burn cycles doing it again.
*/
- if (root->glob->maxParallelHazard == PROPARALLEL_SAFE &&
- root->glob->paramExecTypes == NIL)
+ if (root->glob->maxParallelHazard == PROPARALLEL_SAFE)
return true;
+
/* Else use max_parallel_hazard's search logic, but stop on RESTRICTED */
context.max_hazard = PROPARALLEL_SAFE;
context.max_interesting = PROPARALLEL_RESTRICTED;
- context.safe_param_ids = NIL;
-
- /*
- * The params that refer to the same or parent query level are considered
- * parallel-safe. The idea is that we compute such params at Gather or
- * Gather Merge node and pass their value to workers.
- */
- for (proot = root; proot != NULL; proot = proot->parent_root)
- {
- foreach(l, proot->init_plans)
- {
- SubPlan *initsubplan = (SubPlan *) lfirst(l);
-
- context.safe_param_ids = list_concat(context.safe_param_ids,
- initsubplan->setParam);
- }
- }
return !max_parallel_hazard_walker(node, &context);
}
@@ -775,39 +754,34 @@ max_parallel_hazard_walker(Node *node, max_parallel_hazard_context *context)
}
/*
- * Only parallel-safe SubPlans can be sent to workers. Within the
- * testexpr of the SubPlan, Params representing the output columns of the
- * subplan can be treated as parallel-safe, so temporarily add their IDs
- * to the safe_param_ids list while examining the testexpr.
+ * Only parallel-safe SubPlans can be sent to workers.
*/
else if (IsA(node, SubPlan))
{
SubPlan *subplan = (SubPlan *) node;
- List *save_safe_param_ids;
if (!subplan->parallel_safe &&
max_parallel_hazard_test(PROPARALLEL_RESTRICTED, context))
return true;
- save_safe_param_ids = context->safe_param_ids;
- context->safe_param_ids = list_concat_copy(context->safe_param_ids,
- subplan->paramIds);
+
if (max_parallel_hazard_walker(subplan->testexpr, context))
- return true; /* no need to restore safe_param_ids */
- list_free(context->safe_param_ids);
- context->safe_param_ids = save_safe_param_ids;
- /* we must also check args, but no special Param treatment there */
+ return true;
+
if (max_parallel_hazard_walker((Node *) subplan->args, context))
return true;
+
/* don't want to recurse normally, so we're done */
return false;
}
/*
- * We can't pass Params to workers at the moment either, so they are also
- * parallel-restricted, unless they are PARAM_EXTERN Params or are
- * PARAM_EXEC Params listed in safe_param_ids, meaning they could be
- * either generated within workers or can be computed by the leader and
- * then their value can be passed to workers.
+ * We can't pass all types of Params to workers at the moment either.
+ * PARAM_EXTERN Params are always allowed. PARAM_EXEC Params are parallel-
+ * safe when they can be computed by the leader and their value passed to
+ * workers or are generated within a worker. However we don't always know
+ * whether a param will be generated within a worker when we are parsing a
+ * querytree. In that case we leave it to the consumer to verify that the
+ * current plan level provides these params.
*/
else if (IsA(node, Param))
{
@@ -816,12 +790,12 @@ max_parallel_hazard_walker(Node *node, max_parallel_hazard_context *context)
if (param->paramkind == PARAM_EXTERN)
return false;
- if (param->paramkind != PARAM_EXEC ||
- !list_member_int(context->safe_param_ids, param->paramid))
- {
- if (max_parallel_hazard_test(PROPARALLEL_RESTRICTED, context))
- return true;
- }
+ if (param->paramkind == PARAM_EXEC)
+ return false;
+
+ if (max_parallel_hazard_test(PROPARALLEL_RESTRICTED, context))
+ return true;
+
return false; /* nothing to recurse to */
}
diff --git a/src/test/regress/expected/incremental_sort.out b/src/test/regress/expected/incremental_sort.out
index 0c3433f8e5..2b52b0ca3c 100644
--- a/src/test/regress/expected/incremental_sort.out
+++ b/src/test/regress/expected/incremental_sort.out
@@ -1597,20 +1597,21 @@ explain (costs off) select distinct
unique1,
(select t.unique1 from tenk1 where tenk1.unique1 = t.unique1)
from tenk1 t, generate_series(1, 1000);
- QUERY PLAN
----------------------------------------------------------------------------------
+ QUERY PLAN
+---------------------------------------------------------------------------------------
Unique
- -> Sort
- Sort Key: t.unique1, ((SubPlan 1))
- -> Gather
- Workers Planned: 2
- -> Nested Loop
- -> Parallel Index Only Scan using tenk1_unique1 on tenk1 t
- -> Function Scan on generate_series
- SubPlan 1
- -> Index Only Scan using tenk1_unique1 on tenk1
- Index Cond: (unique1 = t.unique1)
-(11 rows)
+ -> Gather Merge
+ Workers Planned: 2
+ -> Unique
+ -> Sort
+ Sort Key: t.unique1, ((SubPlan 1))
+ -> Nested Loop
+ -> Parallel Index Only Scan using tenk1_unique1 on tenk1 t
+ -> Function Scan on generate_series
+ SubPlan 1
+ -> Index Only Scan using tenk1_unique1 on tenk1
+ Index Cond: (unique1 = t.unique1)
+(12 rows)
explain (costs off) select
unique1,
@@ -1619,16 +1620,16 @@ from tenk1 t, generate_series(1, 1000)
order by 1, 2;
QUERY PLAN
---------------------------------------------------------------------------
- Sort
- Sort Key: t.unique1, ((SubPlan 1))
- -> Gather
- Workers Planned: 2
+ Gather Merge
+ Workers Planned: 2
+ -> Sort
+ Sort Key: t.unique1, ((SubPlan 1))
-> Nested Loop
-> Parallel Index Only Scan using tenk1_unique1 on tenk1 t
-> Function Scan on generate_series
- SubPlan 1
- -> Index Only Scan using tenk1_unique1 on tenk1
- Index Cond: (unique1 = t.unique1)
+ SubPlan 1
+ -> Index Only Scan using tenk1_unique1 on tenk1
+ Index Cond: (unique1 = t.unique1)
(10 rows)
-- Parallel sort but with expression not available until the upper rel.
diff --git a/src/test/regress/expected/partition_prune.out b/src/test/regress/expected/partition_prune.out
index 7555764c77..5c45f9c0a5 100644
--- a/src/test/regress/expected/partition_prune.out
+++ b/src/test/regress/expected/partition_prune.out
@@ -1284,60 +1284,64 @@ EXPLAIN (VERBOSE, COSTS OFF) SELECT * FROM part p(x) ORDER BY x;
--
-- pruning won't work for mc3p, because some keys are Params
explain (costs off) select * from mc2p t1, lateral (select count(*) from mc3p t2 where t2.a = t1.b and abs(t2.b) = 1 and t2.c = 1) s where t1.a = 1;
- QUERY PLAN
------------------------------------------------------------------------
- Nested Loop
- -> Append
- -> Seq Scan on mc2p1 t1_1
- Filter: (a = 1)
- -> Seq Scan on mc2p2 t1_2
- Filter: (a = 1)
- -> Seq Scan on mc2p_default t1_3
- Filter: (a = 1)
- -> Aggregate
- -> Append
- -> Seq Scan on mc3p0 t2_1
- Filter: ((a = t1.b) AND (c = 1) AND (abs(b) = 1))
- -> Seq Scan on mc3p1 t2_2
- Filter: ((a = t1.b) AND (c = 1) AND (abs(b) = 1))
- -> Seq Scan on mc3p2 t2_3
- Filter: ((a = t1.b) AND (c = 1) AND (abs(b) = 1))
- -> Seq Scan on mc3p3 t2_4
- Filter: ((a = t1.b) AND (c = 1) AND (abs(b) = 1))
- -> Seq Scan on mc3p4 t2_5
- Filter: ((a = t1.b) AND (c = 1) AND (abs(b) = 1))
- -> Seq Scan on mc3p5 t2_6
- Filter: ((a = t1.b) AND (c = 1) AND (abs(b) = 1))
- -> Seq Scan on mc3p6 t2_7
- Filter: ((a = t1.b) AND (c = 1) AND (abs(b) = 1))
- -> Seq Scan on mc3p7 t2_8
- Filter: ((a = t1.b) AND (c = 1) AND (abs(b) = 1))
- -> Seq Scan on mc3p_default t2_9
- Filter: ((a = t1.b) AND (c = 1) AND (abs(b) = 1))
-(28 rows)
+ QUERY PLAN
+-----------------------------------------------------------------------------
+ Gather
+ Workers Planned: 2
+ -> Nested Loop
+ -> Parallel Append
+ -> Parallel Seq Scan on mc2p1 t1_1
+ Filter: (a = 1)
+ -> Parallel Seq Scan on mc2p2 t1_2
+ Filter: (a = 1)
+ -> Parallel Seq Scan on mc2p_default t1_3
+ Filter: (a = 1)
+ -> Aggregate
+ -> Append
+ -> Seq Scan on mc3p0 t2_1
+ Filter: ((a = t1.b) AND (c = 1) AND (abs(b) = 1))
+ -> Seq Scan on mc3p1 t2_2
+ Filter: ((a = t1.b) AND (c = 1) AND (abs(b) = 1))
+ -> Seq Scan on mc3p2 t2_3
+ Filter: ((a = t1.b) AND (c = 1) AND (abs(b) = 1))
+ -> Seq Scan on mc3p3 t2_4
+ Filter: ((a = t1.b) AND (c = 1) AND (abs(b) = 1))
+ -> Seq Scan on mc3p4 t2_5
+ Filter: ((a = t1.b) AND (c = 1) AND (abs(b) = 1))
+ -> Seq Scan on mc3p5 t2_6
+ Filter: ((a = t1.b) AND (c = 1) AND (abs(b) = 1))
+ -> Seq Scan on mc3p6 t2_7
+ Filter: ((a = t1.b) AND (c = 1) AND (abs(b) = 1))
+ -> Seq Scan on mc3p7 t2_8
+ Filter: ((a = t1.b) AND (c = 1) AND (abs(b) = 1))
+ -> Seq Scan on mc3p_default t2_9
+ Filter: ((a = t1.b) AND (c = 1) AND (abs(b) = 1))
+(30 rows)
-- pruning should work fine, because values for a prefix of keys (a, b) are
-- available
explain (costs off) select * from mc2p t1, lateral (select count(*) from mc3p t2 where t2.c = t1.b and abs(t2.b) = 1 and t2.a = 1) s where t1.a = 1;
- QUERY PLAN
------------------------------------------------------------------------
- Nested Loop
- -> Append
- -> Seq Scan on mc2p1 t1_1
- Filter: (a = 1)
- -> Seq Scan on mc2p2 t1_2
- Filter: (a = 1)
- -> Seq Scan on mc2p_default t1_3
- Filter: (a = 1)
- -> Aggregate
- -> Append
- -> Seq Scan on mc3p0 t2_1
- Filter: ((c = t1.b) AND (a = 1) AND (abs(b) = 1))
- -> Seq Scan on mc3p1 t2_2
- Filter: ((c = t1.b) AND (a = 1) AND (abs(b) = 1))
- -> Seq Scan on mc3p_default t2_3
- Filter: ((c = t1.b) AND (a = 1) AND (abs(b) = 1))
-(16 rows)
+ QUERY PLAN
+-----------------------------------------------------------------------------
+ Gather
+ Workers Planned: 2
+ -> Nested Loop
+ -> Parallel Append
+ -> Parallel Seq Scan on mc2p1 t1_1
+ Filter: (a = 1)
+ -> Parallel Seq Scan on mc2p2 t1_2
+ Filter: (a = 1)
+ -> Parallel Seq Scan on mc2p_default t1_3
+ Filter: (a = 1)
+ -> Aggregate
+ -> Append
+ -> Seq Scan on mc3p0 t2_1
+ Filter: ((c = t1.b) AND (a = 1) AND (abs(b) = 1))
+ -> Seq Scan on mc3p1 t2_2
+ Filter: ((c = t1.b) AND (a = 1) AND (abs(b) = 1))
+ -> Seq Scan on mc3p_default t2_3
+ Filter: ((c = t1.b) AND (a = 1) AND (abs(b) = 1))
+(18 rows)
-- also here, because values for all keys are provided
explain (costs off) select * from mc2p t1, lateral (select count(*) from mc3p t2 where t2.a = 1 and abs(t2.b) = 1 and t2.c = 1) s where t1.a = 1;
diff --git a/src/test/regress/expected/select_parallel.out b/src/test/regress/expected/select_parallel.out
index 9b4d7dd44a..01443e2ffb 100644
--- a/src/test/regress/expected/select_parallel.out
+++ b/src/test/regress/expected/select_parallel.out
@@ -137,8 +137,8 @@ create table part_pa_test_p2 partition of part_pa_test for values from (0) to (m
explain (costs off)
select (select max((select pa1.b from part_pa_test pa1 where pa1.a = pa2.a)))
from part_pa_test pa2;
- QUERY PLAN
---------------------------------------------------------------
+ QUERY PLAN
+----------------------------------------------------------------
Aggregate
-> Gather
Workers Planned: 3
@@ -148,12 +148,14 @@ explain (costs off)
SubPlan 2
-> Result
SubPlan 1
- -> Append
- -> Seq Scan on part_pa_test_p1 pa1_1
- Filter: (a = pa2.a)
- -> Seq Scan on part_pa_test_p2 pa1_2
- Filter: (a = pa2.a)
-(14 rows)
+ -> Gather
+ Workers Planned: 3
+ -> Parallel Append
+ -> Parallel Seq Scan on part_pa_test_p1 pa1_1
+ Filter: (a = pa2.a)
+ -> Parallel Seq Scan on part_pa_test_p2 pa1_2
+ Filter: (a = pa2.a)
+(16 rows)
drop table part_pa_test;
-- test with leader participation disabled
@@ -320,19 +322,19 @@ explain (costs off, verbose) select
QUERY PLAN
----------------------------------------------------------------------------
Gather
- Output: (SubPlan 1)
+ Output: ((SubPlan 1))
Workers Planned: 4
-> Nested Loop
- Output: t.unique1
+ Output: (SubPlan 1)
-> Parallel Index Only Scan using tenk1_unique1 on public.tenk1 t
Output: t.unique1
-> Function Scan on pg_catalog.generate_series
Output: generate_series.generate_series
Function Call: generate_series(1, 10)
- SubPlan 1
- -> Index Only Scan using tenk1_unique1 on public.tenk1
- Output: t.unique1
- Index Cond: (tenk1.unique1 = t.unique1)
+ SubPlan 1
+ -> Index Only Scan using tenk1_unique1 on public.tenk1
+ Output: t.unique1
+ Index Cond: (tenk1.unique1 = t.unique1)
(14 rows)
explain (costs off, verbose) select
@@ -341,63 +343,69 @@ explain (costs off, verbose) select
QUERY PLAN
----------------------------------------------------------------------
Gather
- Output: (SubPlan 1)
+ Output: ((SubPlan 1))
Workers Planned: 4
-> Parallel Index Only Scan using tenk1_unique1 on public.tenk1 t
- Output: t.unique1
- SubPlan 1
- -> Index Only Scan using tenk1_unique1 on public.tenk1
- Output: t.unique1
- Index Cond: (tenk1.unique1 = t.unique1)
+ Output: (SubPlan 1)
+ SubPlan 1
+ -> Index Only Scan using tenk1_unique1 on public.tenk1
+ Output: t.unique1
+ Index Cond: (tenk1.unique1 = t.unique1)
(9 rows)
explain (costs off, verbose) select
(select t.unique1 from tenk1 where tenk1.unique1 = t.unique1)
from tenk1 t
limit 1;
- QUERY PLAN
--------------------------------------------------------------------
+ QUERY PLAN
+----------------------------------------------------------------------------
Limit
Output: ((SubPlan 1))
- -> Seq Scan on public.tenk1 t
- Output: (SubPlan 1)
- SubPlan 1
- -> Index Only Scan using tenk1_unique1 on public.tenk1
- Output: t.unique1
- Index Cond: (tenk1.unique1 = t.unique1)
-(8 rows)
+ -> Gather
+ Output: ((SubPlan 1))
+ Workers Planned: 4
+ -> Parallel Index Only Scan using tenk1_unique1 on public.tenk1 t
+ Output: (SubPlan 1)
+ SubPlan 1
+ -> Index Only Scan using tenk1_unique1 on public.tenk1
+ Output: t.unique1
+ Index Cond: (tenk1.unique1 = t.unique1)
+(11 rows)
explain (costs off, verbose) select t.unique1
from tenk1 t
where t.unique1 = (select t.unique1 from tenk1 where tenk1.unique1 = t.unique1);
- QUERY PLAN
--------------------------------------------------------------
- Seq Scan on public.tenk1 t
+ QUERY PLAN
+----------------------------------------------------------------------
+ Gather
Output: t.unique1
- Filter: (t.unique1 = (SubPlan 1))
- SubPlan 1
- -> Index Only Scan using tenk1_unique1 on public.tenk1
- Output: t.unique1
- Index Cond: (tenk1.unique1 = t.unique1)
-(7 rows)
+ Workers Planned: 4
+ -> Parallel Index Only Scan using tenk1_unique1 on public.tenk1 t
+ Output: t.unique1
+ Filter: (t.unique1 = (SubPlan 1))
+ SubPlan 1
+ -> Index Only Scan using tenk1_unique1 on public.tenk1
+ Output: t.unique1
+ Index Cond: (tenk1.unique1 = t.unique1)
+(10 rows)
explain (costs off, verbose) select *
from tenk1 t
order by (select t.unique1 from tenk1 where tenk1.unique1 = t.unique1);
- QUERY PLAN
-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
- Sort
+ QUERY PLAN
+----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
+ Gather Merge
Output: t.unique1, t.unique2, t.two, t.four, t.ten, t.twenty, t.hundred, t.thousand, t.twothousand, t.fivethous, t.tenthous, t.odd, t.even, t.stringu1, t.stringu2, t.string4, ((SubPlan 1))
- Sort Key: ((SubPlan 1))
- -> Gather
- Output: t.unique1, t.unique2, t.two, t.four, t.ten, t.twenty, t.hundred, t.thousand, t.twothousand, t.fivethous, t.tenthous, t.odd, t.even, t.stringu1, t.stringu2, t.string4, (SubPlan 1)
- Workers Planned: 4
+ Workers Planned: 4
+ -> Sort
+ Output: t.unique1, t.unique2, t.two, t.four, t.ten, t.twenty, t.hundred, t.thousand, t.twothousand, t.fivethous, t.tenthous, t.odd, t.even, t.stringu1, t.stringu2, t.string4, ((SubPlan 1))
+ Sort Key: ((SubPlan 1))
-> Parallel Seq Scan on public.tenk1 t
- Output: t.unique1, t.unique2, t.two, t.four, t.ten, t.twenty, t.hundred, t.thousand, t.twothousand, t.fivethous, t.tenthous, t.odd, t.even, t.stringu1, t.stringu2, t.string4
- SubPlan 1
- -> Index Only Scan using tenk1_unique1 on public.tenk1
- Output: t.unique1
- Index Cond: (tenk1.unique1 = t.unique1)
+ Output: t.unique1, t.unique2, t.two, t.four, t.ten, t.twenty, t.hundred, t.thousand, t.twothousand, t.fivethous, t.tenthous, t.odd, t.even, t.stringu1, t.stringu2, t.string4, (SubPlan 1)
+ SubPlan 1
+ -> Index Only Scan using tenk1_unique1 on public.tenk1
+ Output: t.unique1
+ Index Cond: (tenk1.unique1 = t.unique1)
(12 rows)
-- test subplan in join/lateral join
@@ -409,14 +417,14 @@ explain (costs off, verbose, timing off) select t.unique1, l.*
QUERY PLAN
----------------------------------------------------------------------
Gather
- Output: t.unique1, (SubPlan 1)
+ Output: t.unique1, ((SubPlan 1))
Workers Planned: 4
-> Parallel Index Only Scan using tenk1_unique1 on public.tenk1 t
- Output: t.unique1
- SubPlan 1
- -> Index Only Scan using tenk1_unique1 on public.tenk1
- Output: t.unique1
- Index Cond: (tenk1.unique1 = t.unique1)
+ Output: t.unique1, (SubPlan 1)
+ SubPlan 1
+ -> Index Only Scan using tenk1_unique1 on public.tenk1
+ Output: t.unique1
+ Index Cond: (tenk1.unique1 = t.unique1)
(9 rows)
-- this is not parallel-safe due to use of random() within SubLink's testexpr:
@@ -1322,8 +1330,10 @@ SELECT 1 FROM tenk1_vw_sec
-> Parallel Index Only Scan using tenk1_unique1 on tenk1
SubPlan 1
-> Aggregate
- -> Seq Scan on int4_tbl
- Filter: (f1 < tenk1_vw_sec.unique1)
-(9 rows)
+ -> Gather
+ Workers Planned: 1
+ -> Parallel Seq Scan on int4_tbl
+ Filter: (f1 < tenk1_vw_sec.unique1)
+(11 rows)
rollback;
--
2.32.1 (Apple Git-133)
^ permalink raw reply [nested|flat] 35+ messages in thread
* Re: Parallelize correlated subqueries that execute within each worker
@ 2023-02-06 16:40 Antonin Houska <[email protected]>
parent: James Coleman <[email protected]>
1 sibling, 1 reply; 35+ messages in thread
From: Antonin Houska @ 2023-02-06 16:40 UTC (permalink / raw)
To: James Coleman <[email protected]>; +Cc: Tomas Vondra <[email protected]>; vignesh C <[email protected]>; Andres Freund <[email protected]>; Robert Haas <[email protected]>; pgsql-hackers; Amit Kapila <[email protected]>; Tom Lane <[email protected]>
James Coleman <[email protected]> wrote:
> On Sat, Jan 21, 2023 at 10:07 PM James Coleman <[email protected]> wrote:
> > ...
> > While working through Tomas's comment about a conditional in the
> > max_parallel_hazard_waker being guaranteed true I realized that in the
> > current version of the patch the safe_param_ids tracking in
> > is_parallel_safe isn't actually needed any longer. That seemed
> > suspicious, and so I started digging, and I found out that in the
> > current approach all of the tests pass with only the changes in
> > clauses.c. I don't believe that the other changes aren't needed;
> > rather I believe there isn't yet a test case exercising them, but I
> > realize that means I can't prove they're needed. I spent some time
> > poking at this, but at least with my current level of imagination I
> > haven't stumbled across a query that would exercise these checks.
>
> I played with this a good bit more yesterday, I'm now a good bit more
> confident this is correct. I've cleaned up the patch; see attached for
> v7.
>
> Here's some of my thought process:
> The comments in src/include/nodes/pathnodes.h:2953 tell us that
> PARAM_EXEC params are used to pass values around from one plan node to
> another in the following ways:
> 1. Values down into subqueries (for outer references in subqueries)
> 2. Up out of subqueries (for the results of a subplan)
> 3. From a NestLoop plan node into its inner relation (when the inner
> scan is parameterized with values from the outer relation)
>
> Case (2) is already known to be safe (we currently add these params to
> safe_param_ids in max_parallel_hazard_walker when we encounter a
> SubPlan node).
>
> I also believe case (3) is already handled. We don't build partial
> paths for joins when joinrel->lateral_relids is non-empty, and join
> order calculations already require that parameterization here go the
> correct way (i.e., inner depends on outer rather than the other way
> around).
>
> That leaves us with only case (1) to consider in this patch. Another
> way of saying this is that this is really the only thing the
> safe_param_ids tracking is guarding against. For params passed down
> into subqueries we can further distinguish between init plans and
> "regular" subplans. We already know that params from init plans are
> safe (at the right level). So we're concerned here with a way to know
> if the params passed to subplans are safe. We already track required
> rels in ParamPathInfo, so it's fairly simple to do this test.
>
> Which this patch we do in fact now see (as expected) rels with
> non-empty lateral_relids showing up in generate_[useful_]gather_paths.
> And the partial paths can now have non-empty required outer rels. I'm
> not able to come up with a plan that would actually be caught by those
> checks; I theorize that because of the few places we actually call
> generate_[useful_]gather_paths we are in practice already excluding
> those, but for now I've left these as a conditional rather than an
> assertion because it seems like the kind of guard we'd want to ensure
> those methods are safe.
Maybe we can later (in separate patches) relax the restrictions imposed on
partial path creation a little bit, so that more parameterized partial paths
are created.
One particular case that should be rejected by your checks is a partial index
path, which can be parameterized, but I couldn't construct a query that makes
your checks fire. Maybe the reason is that a parameterized index path is
mostly used on the inner side of a NL join, however no partial path can be
used there. (The problem is that each worker evaluating the NL join would only
see a subset of the inner relation, which whould lead to incorrect results.)
So I'd also choose conditions rather than assert statements.
Following are my (minor) findings:
In generate_gather_paths() you added this test
/*
* Delay gather path creation until the level in the join tree where all
* params used in a worker are generated within that worker.
*/
if (!bms_is_subset(required_outer, rel->relids))
return;
but I'm not sure if required_outer can contain anything of rel->relids. How
about using bms_is_empty(required) outer, or even this?
if (required_outer)
return;
Similarly,
/* We can't pass params to workers. */
if (!bms_is_subset(PATH_REQ_OUTER(cheapest_partial_path), rel->relids))
might look like
if (!bms_is_empty(PATH_REQ_OUTER(cheapest_partial_path)))
or
if (PATH_REQ_OUTER(cheapest_partial_path))
In particular, build_index_paths() does the following when setting
outer_relids (which eventually becomes (path->param_info->ppi_req_outer):
/* Enforce convention that outer_relids is exactly NULL if empty */
if (bms_is_empty(outer_relids))
outer_relids = NULL;
Another question is whether in this call
simple_gather_path = (Path *)
create_gather_path(root, rel, cheapest_partial_path, rel->reltarget,
required_outer, rowsp);
required_outer should be passed to create_gather_path(). Shouldn't it rather
be PATH_REQ_OUTER(cheapest_partial_path) that you test just above? Again,
build_index_paths() initializes outer_relids this way
outer_relids = bms_copy(rel->lateral_relids);
but then it may add some more relations:
/* OK to include this clause */
index_clauses = lappend(index_clauses, iclause);
outer_relids = bms_add_members(outer_relids,
rinfo->clause_relids);
So I think that PATH_REQ_OUTER(cheapest_partial_path) in
generate_gather_paths() can eventually contain more relations than
required_outer, and therefore it's safer to check the first.
Similar comments might apply to generate_useful_gather_paths(). Here I also
suggest to move this test
/* We can't pass params to workers. */
if (!bms_is_subset(PATH_REQ_OUTER(subpath), rel->relids))
continue;
to the top of the loop because it's relatively cheap.
--
Antonin Houska
Web: https://www.cybertec-postgresql.com
^ permalink raw reply [nested|flat] 35+ messages in thread
* Re: Parallelize correlated subqueries that execute within each worker
@ 2023-02-08 13:38 James Coleman <[email protected]>
parent: Antonin Houska <[email protected]>
0 siblings, 1 reply; 35+ messages in thread
From: James Coleman @ 2023-02-08 13:38 UTC (permalink / raw)
To: Antonin Houska <[email protected]>; +Cc: Tomas Vondra <[email protected]>; vignesh C <[email protected]>; Andres Freund <[email protected]>; Robert Haas <[email protected]>; pgsql-hackers; Amit Kapila <[email protected]>; Tom Lane <[email protected]>
On Mon, Feb 6, 2023 at 11:39 AM Antonin Houska <[email protected]> wrote:
>
> James Coleman <[email protected]> wrote:
> > Which this patch we do in fact now see (as expected) rels with
> > non-empty lateral_relids showing up in generate_[useful_]gather_paths.
> > And the partial paths can now have non-empty required outer rels. I'm
> > not able to come up with a plan that would actually be caught by those
> > checks; I theorize that because of the few places we actually call
> > generate_[useful_]gather_paths we are in practice already excluding
> > those, but for now I've left these as a conditional rather than an
> > assertion because it seems like the kind of guard we'd want to ensure
> > those methods are safe.
>
> Maybe we can later (in separate patches) relax the restrictions imposed on
> partial path creation a little bit, so that more parameterized partial paths
> are created.
>
> One particular case that should be rejected by your checks is a partial index
> path, which can be parameterized, but I couldn't construct a query that makes
> your checks fire. Maybe the reason is that a parameterized index path is
> mostly used on the inner side of a NL join, however no partial path can be
> used there. (The problem is that each worker evaluating the NL join would only
> see a subset of the inner relation, which whould lead to incorrect results.)
>
> So I'd also choose conditions rather than assert statements.
Thanks for confirming.
>
> Following are my (minor) findings:
>
> In generate_gather_paths() you added this test
>
> /*
> * Delay gather path creation until the level in the join tree where all
> * params used in a worker are generated within that worker.
> */
> if (!bms_is_subset(required_outer, rel->relids))
> return;
>
> but I'm not sure if required_outer can contain anything of rel->relids. How
> about using bms_is_empty(required) outer, or even this?
>
> if (required_outer)
> return;
>
> Similarly,
>
> /* We can't pass params to workers. */
> if (!bms_is_subset(PATH_REQ_OUTER(cheapest_partial_path), rel->relids))
>
> might look like
>
> if (!bms_is_empty(PATH_REQ_OUTER(cheapest_partial_path)))
>
> or
>
> if (PATH_REQ_OUTER(cheapest_partial_path))
I'm not sure about this change. Deciding is difficult given the fact
that we don't seem to currently generate these paths, but I don't see
a reason why lateral_relids can't be present on the rel, and if so,
then we need to check to see if they're a subset of relids we can
satisfy rather than checking that they don't exist.
> In particular, build_index_paths() does the following when setting
> outer_relids (which eventually becomes (path->param_info->ppi_req_outer):
>
> /* Enforce convention that outer_relids is exactly NULL if empty */
> if (bms_is_empty(outer_relids))
> outer_relids = NULL;
>
>
> Another question is whether in this call
>
> simple_gather_path = (Path *)
> create_gather_path(root, rel, cheapest_partial_path, rel->reltarget,
> required_outer, rowsp);
>
> required_outer should be passed to create_gather_path(). Shouldn't it rather
> be PATH_REQ_OUTER(cheapest_partial_path) that you test just above? Again,
> build_index_paths() initializes outer_relids this way
>
> outer_relids = bms_copy(rel->lateral_relids);
>
> but then it may add some more relations:
>
> /* OK to include this clause */
> index_clauses = lappend(index_clauses, iclause);
> outer_relids = bms_add_members(outer_relids,
> rinfo->clause_relids);
>
> So I think that PATH_REQ_OUTER(cheapest_partial_path) in
> generate_gather_paths() can eventually contain more relations than
> required_outer, and therefore it's safer to check the first.
Yes, this is a good catch. Originally I didn't know about
PATH_REQ_OUTER, and I'd missed using it in these places.
>
> Similar comments might apply to generate_useful_gather_paths(). Here I also
> suggest to move this test
>
> /* We can't pass params to workers. */
> if (!bms_is_subset(PATH_REQ_OUTER(subpath), rel->relids))
> continue;
>
> to the top of the loop because it's relatively cheap.
Moved.
Attached is v9.
James Coleman
Attachments:
[application/octet-stream] v9-0001-Add-tests-before-change.patch (7.2K, ../../CAAaqYe8fF=qc2Z+ttmrBkCMhV976Sy83uS1w9CyXMV7=X7NSMg@mail.gmail.com/2-v9-0001-Add-tests-before-change.patch)
download | inline diff:
From d7a74b2f26edaf36d5098b4b45e19c437a4ebbdf Mon Sep 17 00:00:00 2001
From: jcoleman <[email protected]>
Date: Mon, 26 Sep 2022 20:30:23 -0400
Subject: [PATCH v9 1/2] Add tests before change
---
src/test/regress/expected/select_parallel.out | 108 ++++++++++++++++++
src/test/regress/sql/select_parallel.sql | 25 ++++
2 files changed, 133 insertions(+)
diff --git a/src/test/regress/expected/select_parallel.out b/src/test/regress/expected/select_parallel.out
index 91f74fe47a..9b4d7dd44a 100644
--- a/src/test/regress/expected/select_parallel.out
+++ b/src/test/regress/expected/select_parallel.out
@@ -311,6 +311,114 @@ select count(*) from tenk1 where (two, four) not in
10000
(1 row)
+-- test parallel plans for queries containing correlated subplans
+-- where the subplan only needs params available from the current
+-- worker's scan.
+explain (costs off, verbose) select
+ (select t.unique1 from tenk1 where tenk1.unique1 = t.unique1)
+ from tenk1 t, generate_series(1, 10);
+ QUERY PLAN
+----------------------------------------------------------------------------
+ Gather
+ Output: (SubPlan 1)
+ Workers Planned: 4
+ -> Nested Loop
+ Output: t.unique1
+ -> Parallel Index Only Scan using tenk1_unique1 on public.tenk1 t
+ Output: t.unique1
+ -> Function Scan on pg_catalog.generate_series
+ Output: generate_series.generate_series
+ Function Call: generate_series(1, 10)
+ SubPlan 1
+ -> Index Only Scan using tenk1_unique1 on public.tenk1
+ Output: t.unique1
+ Index Cond: (tenk1.unique1 = t.unique1)
+(14 rows)
+
+explain (costs off, verbose) select
+ (select t.unique1 from tenk1 where tenk1.unique1 = t.unique1)
+ from tenk1 t;
+ QUERY PLAN
+----------------------------------------------------------------------
+ Gather
+ Output: (SubPlan 1)
+ Workers Planned: 4
+ -> Parallel Index Only Scan using tenk1_unique1 on public.tenk1 t
+ Output: t.unique1
+ SubPlan 1
+ -> Index Only Scan using tenk1_unique1 on public.tenk1
+ Output: t.unique1
+ Index Cond: (tenk1.unique1 = t.unique1)
+(9 rows)
+
+explain (costs off, verbose) select
+ (select t.unique1 from tenk1 where tenk1.unique1 = t.unique1)
+ from tenk1 t
+ limit 1;
+ QUERY PLAN
+-------------------------------------------------------------------
+ Limit
+ Output: ((SubPlan 1))
+ -> Seq Scan on public.tenk1 t
+ Output: (SubPlan 1)
+ SubPlan 1
+ -> Index Only Scan using tenk1_unique1 on public.tenk1
+ Output: t.unique1
+ Index Cond: (tenk1.unique1 = t.unique1)
+(8 rows)
+
+explain (costs off, verbose) select t.unique1
+ from tenk1 t
+ where t.unique1 = (select t.unique1 from tenk1 where tenk1.unique1 = t.unique1);
+ QUERY PLAN
+-------------------------------------------------------------
+ Seq Scan on public.tenk1 t
+ Output: t.unique1
+ Filter: (t.unique1 = (SubPlan 1))
+ SubPlan 1
+ -> Index Only Scan using tenk1_unique1 on public.tenk1
+ Output: t.unique1
+ Index Cond: (tenk1.unique1 = t.unique1)
+(7 rows)
+
+explain (costs off, verbose) select *
+ from tenk1 t
+ order by (select t.unique1 from tenk1 where tenk1.unique1 = t.unique1);
+ QUERY PLAN
+----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
+ Sort
+ Output: t.unique1, t.unique2, t.two, t.four, t.ten, t.twenty, t.hundred, t.thousand, t.twothousand, t.fivethous, t.tenthous, t.odd, t.even, t.stringu1, t.stringu2, t.string4, ((SubPlan 1))
+ Sort Key: ((SubPlan 1))
+ -> Gather
+ Output: t.unique1, t.unique2, t.two, t.four, t.ten, t.twenty, t.hundred, t.thousand, t.twothousand, t.fivethous, t.tenthous, t.odd, t.even, t.stringu1, t.stringu2, t.string4, (SubPlan 1)
+ Workers Planned: 4
+ -> Parallel Seq Scan on public.tenk1 t
+ Output: t.unique1, t.unique2, t.two, t.four, t.ten, t.twenty, t.hundred, t.thousand, t.twothousand, t.fivethous, t.tenthous, t.odd, t.even, t.stringu1, t.stringu2, t.string4
+ SubPlan 1
+ -> Index Only Scan using tenk1_unique1 on public.tenk1
+ Output: t.unique1
+ Index Cond: (tenk1.unique1 = t.unique1)
+(12 rows)
+
+-- test subplan in join/lateral join
+explain (costs off, verbose, timing off) select t.unique1, l.*
+ from tenk1 t
+ join lateral (
+ select (select t.unique1 from tenk1 where tenk1.unique1 = t.unique1 offset 0)
+ ) l on true;
+ QUERY PLAN
+----------------------------------------------------------------------
+ Gather
+ Output: t.unique1, (SubPlan 1)
+ Workers Planned: 4
+ -> Parallel Index Only Scan using tenk1_unique1 on public.tenk1 t
+ Output: t.unique1
+ SubPlan 1
+ -> Index Only Scan using tenk1_unique1 on public.tenk1
+ Output: t.unique1
+ Index Cond: (tenk1.unique1 = t.unique1)
+(9 rows)
+
-- this is not parallel-safe due to use of random() within SubLink's testexpr:
explain (costs off)
select * from tenk1 where (unique1 + random())::integer not in
diff --git a/src/test/regress/sql/select_parallel.sql b/src/test/regress/sql/select_parallel.sql
index 62fb68c7a0..21c2f1c742 100644
--- a/src/test/regress/sql/select_parallel.sql
+++ b/src/test/regress/sql/select_parallel.sql
@@ -111,6 +111,31 @@ explain (costs off)
(select hundred, thousand from tenk2 where thousand > 100);
select count(*) from tenk1 where (two, four) not in
(select hundred, thousand from tenk2 where thousand > 100);
+-- test parallel plans for queries containing correlated subplans
+-- where the subplan only needs params available from the current
+-- worker's scan.
+explain (costs off, verbose) select
+ (select t.unique1 from tenk1 where tenk1.unique1 = t.unique1)
+ from tenk1 t, generate_series(1, 10);
+explain (costs off, verbose) select
+ (select t.unique1 from tenk1 where tenk1.unique1 = t.unique1)
+ from tenk1 t;
+explain (costs off, verbose) select
+ (select t.unique1 from tenk1 where tenk1.unique1 = t.unique1)
+ from tenk1 t
+ limit 1;
+explain (costs off, verbose) select t.unique1
+ from tenk1 t
+ where t.unique1 = (select t.unique1 from tenk1 where tenk1.unique1 = t.unique1);
+explain (costs off, verbose) select *
+ from tenk1 t
+ order by (select t.unique1 from tenk1 where tenk1.unique1 = t.unique1);
+-- test subplan in join/lateral join
+explain (costs off, verbose, timing off) select t.unique1, l.*
+ from tenk1 t
+ join lateral (
+ select (select t.unique1 from tenk1 where tenk1.unique1 = t.unique1 offset 0)
+ ) l on true;
-- this is not parallel-safe due to use of random() within SubLink's testexpr:
explain (costs off)
select * from tenk1 where (unique1 + random())::integer not in
--
2.32.1 (Apple Git-133)
[application/octet-stream] v9-0002-Parallelize-correlated-subqueries.patch (30.5K, ../../CAAaqYe8fF=qc2Z+ttmrBkCMhV976Sy83uS1w9CyXMV7=X7NSMg@mail.gmail.com/3-v9-0002-Parallelize-correlated-subqueries.patch)
download | inline diff:
From 8b36aa8fa43bfe6a32a1dbce0623ad9243f0b303 Mon Sep 17 00:00:00 2001
From: jcoleman <[email protected]>
Date: Wed, 18 Jan 2023 20:43:26 -0500
Subject: [PATCH v9 2/2] Parallelize correlated subqueries
When params are provided at the current query level (i.e., are generated
within a single worker and not shared across workers) we can safely
execute these in parallel.
Alternative approach using just relids subset check
---
doc/src/sgml/parallel.sgml | 3 +-
src/backend/optimizer/path/allpaths.c | 46 +++++--
src/backend/optimizer/path/joinpath.c | 10 +-
src/backend/optimizer/plan/planner.c | 8 ++
src/backend/optimizer/util/clauses.c | 74 ++++------
.../regress/expected/incremental_sort.out | 41 +++---
src/test/regress/expected/partition_prune.out | 104 +++++++-------
src/test/regress/expected/select_parallel.out | 128 ++++++++++--------
8 files changed, 222 insertions(+), 192 deletions(-)
diff --git a/doc/src/sgml/parallel.sgml b/doc/src/sgml/parallel.sgml
index 5acc9537d6..fd32572ec8 100644
--- a/doc/src/sgml/parallel.sgml
+++ b/doc/src/sgml/parallel.sgml
@@ -518,7 +518,8 @@ EXPLAIN SELECT * FROM pgbench_accounts WHERE filler LIKE '%x%';
<listitem>
<para>
- Plan nodes that reference a correlated <literal>SubPlan</literal>.
+ Plan nodes that reference a correlated <literal>SubPlan</literal> where
+ the result is shared between workers.
</para>
</listitem>
</itemizedlist>
diff --git a/src/backend/optimizer/path/allpaths.c b/src/backend/optimizer/path/allpaths.c
index c2fc568dc8..a579d4c092 100644
--- a/src/backend/optimizer/path/allpaths.c
+++ b/src/backend/optimizer/path/allpaths.c
@@ -3018,11 +3018,19 @@ generate_gather_paths(PlannerInfo *root, RelOptInfo *rel, bool override_rows)
ListCell *lc;
double rows;
double *rowsp = NULL;
+ Relids required_outer = rel->lateral_relids;
/* If there are no partial paths, there's nothing to do here. */
if (rel->partial_pathlist == NIL)
return;
+ /*
+ * Delay gather path creation until the level in the join tree where all
+ * params used in a worker are generated within that worker.
+ */
+ if (!bms_is_subset(required_outer, rel->relids))
+ return;
+
/* Should we override the rel's rowcount estimate? */
if (override_rows)
rowsp = &rows;
@@ -3033,12 +3041,17 @@ generate_gather_paths(PlannerInfo *root, RelOptInfo *rel, bool override_rows)
* of partial_pathlist because of the way add_partial_path works.
*/
cheapest_partial_path = linitial(rel->partial_pathlist);
- rows =
- cheapest_partial_path->rows * cheapest_partial_path->parallel_workers;
- simple_gather_path = (Path *)
- create_gather_path(root, rel, cheapest_partial_path, rel->reltarget,
- NULL, rowsp);
- add_path(rel, simple_gather_path);
+
+ /* We can't pass params to workers. */
+ if (bms_is_subset(PATH_REQ_OUTER(cheapest_partial_path), rel->relids))
+ {
+ rows =
+ cheapest_partial_path->rows * cheapest_partial_path->parallel_workers;
+ simple_gather_path = (Path *)
+ create_gather_path(root, rel, cheapest_partial_path, rel->reltarget,
+ PATH_REQ_OUTER(cheapest_partial_path), rowsp);
+ add_path(rel, simple_gather_path);
+ }
/*
* For each useful ordering, we can consider an order-preserving Gather
@@ -3052,9 +3065,14 @@ generate_gather_paths(PlannerInfo *root, RelOptInfo *rel, bool override_rows)
if (subpath->pathkeys == NIL)
continue;
+ /* We can't pass params to workers. */
+ if (!bms_is_subset(PATH_REQ_OUTER(subpath), rel->relids))
+ continue;
+
rows = subpath->rows * subpath->parallel_workers;
path = create_gather_merge_path(root, rel, subpath, rel->reltarget,
- subpath->pathkeys, NULL, rowsp);
+ subpath->pathkeys,
+ PATH_REQ_OUTER(subpath), rowsp);
add_path(rel, &path->path);
}
}
@@ -3156,11 +3174,19 @@ generate_useful_gather_paths(PlannerInfo *root, RelOptInfo *rel, bool override_r
double *rowsp = NULL;
List *useful_pathkeys_list = NIL;
Path *cheapest_partial_path = NULL;
+ Relids required_outer = rel->lateral_relids;
/* If there are no partial paths, there's nothing to do here. */
if (rel->partial_pathlist == NIL)
return;
+ /*
+ * Delay gather path creation until the level in the join tree where all
+ * params used in a worker are generated within that worker.
+ */
+ if (!bms_is_subset(required_outer, rel->relids))
+ return;
+
/* Should we override the rel's rowcount estimate? */
if (override_rows)
rowsp = &rows;
@@ -3190,6 +3216,10 @@ generate_useful_gather_paths(PlannerInfo *root, RelOptInfo *rel, bool override_r
Path *subpath = (Path *) lfirst(lc2);
GatherMergePath *path;
+ /* We can't pass params to workers. */
+ if (!bms_is_subset(PATH_REQ_OUTER(subpath), rel->relids))
+ continue;
+
is_sorted = pathkeys_count_contained_in(useful_pathkeys,
subpath->pathkeys,
&presorted_keys);
@@ -3249,7 +3279,7 @@ generate_useful_gather_paths(PlannerInfo *root, RelOptInfo *rel, bool override_r
subpath,
rel->reltarget,
subpath->pathkeys,
- NULL,
+ PATH_REQ_OUTER(subpath),
rowsp);
add_path(rel, &path->path);
diff --git a/src/backend/optimizer/path/joinpath.c b/src/backend/optimizer/path/joinpath.c
index d345c0437a..644b90ad1e 100644
--- a/src/backend/optimizer/path/joinpath.c
+++ b/src/backend/optimizer/path/joinpath.c
@@ -1791,10 +1791,12 @@ match_unsorted_outer(PlannerInfo *root,
* Consider partial nestloop and mergejoin plan if outerrel has any
* partial path and the joinrel is parallel-safe. However, we can't
* handle JOIN_UNIQUE_OUTER, because the outer path will be partial, and
- * therefore we won't be able to properly guarantee uniqueness. Nor can
- * we handle joins needing lateral rels, since partial paths must not be
- * parameterized. Similarly, we can't handle JOIN_FULL and JOIN_RIGHT,
- * because they can produce false null extended rows.
+ * therefore we won't be able to properly guarantee uniqueness. Similarly,
+ * we can't handle JOIN_FULL and JOIN_RIGHT, because they can produce false
+ * null extended rows.
+ *
+ * While partial paths may now be parameterized so long as all of the params
+ * can be generated wholly within a worker we punt on supporting that here.
*/
if (joinrel->consider_parallel &&
save_jointype != JOIN_UNIQUE_OUTER &&
diff --git a/src/backend/optimizer/plan/planner.c b/src/backend/optimizer/plan/planner.c
index 05f44faf6e..fcde41d9f3 100644
--- a/src/backend/optimizer/plan/planner.c
+++ b/src/backend/optimizer/plan/planner.c
@@ -7344,11 +7344,16 @@ gather_grouping_paths(PlannerInfo *root, RelOptInfo *rel)
ListCell *lc;
Path *cheapest_partial_path;
+ /* By grouping time we shouldn't have any lateral dependencies. */
+ Assert(rel->lateral_relids == NULL);
+
/* Try Gather for unordered paths and Gather Merge for ordered ones. */
generate_useful_gather_paths(root, rel, true);
/* Try cheapest partial path + explicit Sort + Gather Merge. */
cheapest_partial_path = linitial(rel->partial_pathlist);
+ /* By grouping time we shouldn't have any lateral dependencies. */
+ Assert(PATH_REQ_OUTER(cheapest_partial_path) == NULL);
if (!pathkeys_contained_in(root->group_pathkeys,
cheapest_partial_path->pathkeys))
{
@@ -7400,6 +7405,9 @@ gather_grouping_paths(PlannerInfo *root, RelOptInfo *rel)
if (presorted_keys == 0)
continue;
+ /* By grouping time we shouldn't have any lateral dependencies. */
+ Assert(PATH_REQ_OUTER(path) == NULL);
+
path = (Path *) create_incremental_sort_path(root,
rel,
path,
diff --git a/src/backend/optimizer/util/clauses.c b/src/backend/optimizer/util/clauses.c
index aa584848cf..4a3a0489a8 100644
--- a/src/backend/optimizer/util/clauses.c
+++ b/src/backend/optimizer/util/clauses.c
@@ -89,7 +89,6 @@ typedef struct
{
char max_hazard; /* worst proparallel hazard found so far */
char max_interesting; /* worst proparallel hazard of interest */
- List *safe_param_ids; /* PARAM_EXEC Param IDs to treat as safe */
} max_parallel_hazard_context;
static bool contain_agg_clause_walker(Node *node, void *context);
@@ -618,7 +617,6 @@ max_parallel_hazard(Query *parse)
context.max_hazard = PROPARALLEL_SAFE;
context.max_interesting = PROPARALLEL_UNSAFE;
- context.safe_param_ids = NIL;
(void) max_parallel_hazard_walker((Node *) parse, &context);
return context.max_hazard;
}
@@ -629,43 +627,24 @@ max_parallel_hazard(Query *parse)
*
* root->glob->maxParallelHazard must previously have been set to the
* result of max_parallel_hazard() on the whole query.
+ *
+ * The caller is responsible for verifying that PARAM_EXEC Params are generated
+ * at the current plan level.
*/
bool
is_parallel_safe(PlannerInfo *root, Node *node)
{
max_parallel_hazard_context context;
- PlannerInfo *proot;
- ListCell *l;
/*
- * Even if the original querytree contained nothing unsafe, we need to
- * search the expression if we have generated any PARAM_EXEC Params while
- * planning, because those are parallel-restricted and there might be one
- * in this expression. But otherwise we don't need to look.
+ * If we've already checked the querytree don't burn cycles doing it again.
*/
- if (root->glob->maxParallelHazard == PROPARALLEL_SAFE &&
- root->glob->paramExecTypes == NIL)
+ if (root->glob->maxParallelHazard == PROPARALLEL_SAFE)
return true;
+
/* Else use max_parallel_hazard's search logic, but stop on RESTRICTED */
context.max_hazard = PROPARALLEL_SAFE;
context.max_interesting = PROPARALLEL_RESTRICTED;
- context.safe_param_ids = NIL;
-
- /*
- * The params that refer to the same or parent query level are considered
- * parallel-safe. The idea is that we compute such params at Gather or
- * Gather Merge node and pass their value to workers.
- */
- for (proot = root; proot != NULL; proot = proot->parent_root)
- {
- foreach(l, proot->init_plans)
- {
- SubPlan *initsubplan = (SubPlan *) lfirst(l);
-
- context.safe_param_ids = list_concat(context.safe_param_ids,
- initsubplan->setParam);
- }
- }
return !max_parallel_hazard_walker(node, &context);
}
@@ -775,39 +754,34 @@ max_parallel_hazard_walker(Node *node, max_parallel_hazard_context *context)
}
/*
- * Only parallel-safe SubPlans can be sent to workers. Within the
- * testexpr of the SubPlan, Params representing the output columns of the
- * subplan can be treated as parallel-safe, so temporarily add their IDs
- * to the safe_param_ids list while examining the testexpr.
+ * Only parallel-safe SubPlans can be sent to workers.
*/
else if (IsA(node, SubPlan))
{
SubPlan *subplan = (SubPlan *) node;
- List *save_safe_param_ids;
if (!subplan->parallel_safe &&
max_parallel_hazard_test(PROPARALLEL_RESTRICTED, context))
return true;
- save_safe_param_ids = context->safe_param_ids;
- context->safe_param_ids = list_concat_copy(context->safe_param_ids,
- subplan->paramIds);
+
if (max_parallel_hazard_walker(subplan->testexpr, context))
- return true; /* no need to restore safe_param_ids */
- list_free(context->safe_param_ids);
- context->safe_param_ids = save_safe_param_ids;
- /* we must also check args, but no special Param treatment there */
+ return true;
+
if (max_parallel_hazard_walker((Node *) subplan->args, context))
return true;
+
/* don't want to recurse normally, so we're done */
return false;
}
/*
- * We can't pass Params to workers at the moment either, so they are also
- * parallel-restricted, unless they are PARAM_EXTERN Params or are
- * PARAM_EXEC Params listed in safe_param_ids, meaning they could be
- * either generated within workers or can be computed by the leader and
- * then their value can be passed to workers.
+ * We can't pass all types of Params to workers at the moment either.
+ * PARAM_EXTERN Params are always allowed. PARAM_EXEC Params are parallel-
+ * safe when they can be computed by the leader and their value passed to
+ * workers or are generated within a worker. However we don't always know
+ * whether a param will be generated within a worker when we are parsing a
+ * querytree. In that case we leave it to the consumer to verify that the
+ * current plan level provides these params.
*/
else if (IsA(node, Param))
{
@@ -816,12 +790,12 @@ max_parallel_hazard_walker(Node *node, max_parallel_hazard_context *context)
if (param->paramkind == PARAM_EXTERN)
return false;
- if (param->paramkind != PARAM_EXEC ||
- !list_member_int(context->safe_param_ids, param->paramid))
- {
- if (max_parallel_hazard_test(PROPARALLEL_RESTRICTED, context))
- return true;
- }
+ if (param->paramkind == PARAM_EXEC)
+ return false;
+
+ if (max_parallel_hazard_test(PROPARALLEL_RESTRICTED, context))
+ return true;
+
return false; /* nothing to recurse to */
}
diff --git a/src/test/regress/expected/incremental_sort.out b/src/test/regress/expected/incremental_sort.out
index 0c3433f8e5..2b52b0ca3c 100644
--- a/src/test/regress/expected/incremental_sort.out
+++ b/src/test/regress/expected/incremental_sort.out
@@ -1597,20 +1597,21 @@ explain (costs off) select distinct
unique1,
(select t.unique1 from tenk1 where tenk1.unique1 = t.unique1)
from tenk1 t, generate_series(1, 1000);
- QUERY PLAN
----------------------------------------------------------------------------------
+ QUERY PLAN
+---------------------------------------------------------------------------------------
Unique
- -> Sort
- Sort Key: t.unique1, ((SubPlan 1))
- -> Gather
- Workers Planned: 2
- -> Nested Loop
- -> Parallel Index Only Scan using tenk1_unique1 on tenk1 t
- -> Function Scan on generate_series
- SubPlan 1
- -> Index Only Scan using tenk1_unique1 on tenk1
- Index Cond: (unique1 = t.unique1)
-(11 rows)
+ -> Gather Merge
+ Workers Planned: 2
+ -> Unique
+ -> Sort
+ Sort Key: t.unique1, ((SubPlan 1))
+ -> Nested Loop
+ -> Parallel Index Only Scan using tenk1_unique1 on tenk1 t
+ -> Function Scan on generate_series
+ SubPlan 1
+ -> Index Only Scan using tenk1_unique1 on tenk1
+ Index Cond: (unique1 = t.unique1)
+(12 rows)
explain (costs off) select
unique1,
@@ -1619,16 +1620,16 @@ from tenk1 t, generate_series(1, 1000)
order by 1, 2;
QUERY PLAN
---------------------------------------------------------------------------
- Sort
- Sort Key: t.unique1, ((SubPlan 1))
- -> Gather
- Workers Planned: 2
+ Gather Merge
+ Workers Planned: 2
+ -> Sort
+ Sort Key: t.unique1, ((SubPlan 1))
-> Nested Loop
-> Parallel Index Only Scan using tenk1_unique1 on tenk1 t
-> Function Scan on generate_series
- SubPlan 1
- -> Index Only Scan using tenk1_unique1 on tenk1
- Index Cond: (unique1 = t.unique1)
+ SubPlan 1
+ -> Index Only Scan using tenk1_unique1 on tenk1
+ Index Cond: (unique1 = t.unique1)
(10 rows)
-- Parallel sort but with expression not available until the upper rel.
diff --git a/src/test/regress/expected/partition_prune.out b/src/test/regress/expected/partition_prune.out
index 7555764c77..5c45f9c0a5 100644
--- a/src/test/regress/expected/partition_prune.out
+++ b/src/test/regress/expected/partition_prune.out
@@ -1284,60 +1284,64 @@ EXPLAIN (VERBOSE, COSTS OFF) SELECT * FROM part p(x) ORDER BY x;
--
-- pruning won't work for mc3p, because some keys are Params
explain (costs off) select * from mc2p t1, lateral (select count(*) from mc3p t2 where t2.a = t1.b and abs(t2.b) = 1 and t2.c = 1) s where t1.a = 1;
- QUERY PLAN
------------------------------------------------------------------------
- Nested Loop
- -> Append
- -> Seq Scan on mc2p1 t1_1
- Filter: (a = 1)
- -> Seq Scan on mc2p2 t1_2
- Filter: (a = 1)
- -> Seq Scan on mc2p_default t1_3
- Filter: (a = 1)
- -> Aggregate
- -> Append
- -> Seq Scan on mc3p0 t2_1
- Filter: ((a = t1.b) AND (c = 1) AND (abs(b) = 1))
- -> Seq Scan on mc3p1 t2_2
- Filter: ((a = t1.b) AND (c = 1) AND (abs(b) = 1))
- -> Seq Scan on mc3p2 t2_3
- Filter: ((a = t1.b) AND (c = 1) AND (abs(b) = 1))
- -> Seq Scan on mc3p3 t2_4
- Filter: ((a = t1.b) AND (c = 1) AND (abs(b) = 1))
- -> Seq Scan on mc3p4 t2_5
- Filter: ((a = t1.b) AND (c = 1) AND (abs(b) = 1))
- -> Seq Scan on mc3p5 t2_6
- Filter: ((a = t1.b) AND (c = 1) AND (abs(b) = 1))
- -> Seq Scan on mc3p6 t2_7
- Filter: ((a = t1.b) AND (c = 1) AND (abs(b) = 1))
- -> Seq Scan on mc3p7 t2_8
- Filter: ((a = t1.b) AND (c = 1) AND (abs(b) = 1))
- -> Seq Scan on mc3p_default t2_9
- Filter: ((a = t1.b) AND (c = 1) AND (abs(b) = 1))
-(28 rows)
+ QUERY PLAN
+-----------------------------------------------------------------------------
+ Gather
+ Workers Planned: 2
+ -> Nested Loop
+ -> Parallel Append
+ -> Parallel Seq Scan on mc2p1 t1_1
+ Filter: (a = 1)
+ -> Parallel Seq Scan on mc2p2 t1_2
+ Filter: (a = 1)
+ -> Parallel Seq Scan on mc2p_default t1_3
+ Filter: (a = 1)
+ -> Aggregate
+ -> Append
+ -> Seq Scan on mc3p0 t2_1
+ Filter: ((a = t1.b) AND (c = 1) AND (abs(b) = 1))
+ -> Seq Scan on mc3p1 t2_2
+ Filter: ((a = t1.b) AND (c = 1) AND (abs(b) = 1))
+ -> Seq Scan on mc3p2 t2_3
+ Filter: ((a = t1.b) AND (c = 1) AND (abs(b) = 1))
+ -> Seq Scan on mc3p3 t2_4
+ Filter: ((a = t1.b) AND (c = 1) AND (abs(b) = 1))
+ -> Seq Scan on mc3p4 t2_5
+ Filter: ((a = t1.b) AND (c = 1) AND (abs(b) = 1))
+ -> Seq Scan on mc3p5 t2_6
+ Filter: ((a = t1.b) AND (c = 1) AND (abs(b) = 1))
+ -> Seq Scan on mc3p6 t2_7
+ Filter: ((a = t1.b) AND (c = 1) AND (abs(b) = 1))
+ -> Seq Scan on mc3p7 t2_8
+ Filter: ((a = t1.b) AND (c = 1) AND (abs(b) = 1))
+ -> Seq Scan on mc3p_default t2_9
+ Filter: ((a = t1.b) AND (c = 1) AND (abs(b) = 1))
+(30 rows)
-- pruning should work fine, because values for a prefix of keys (a, b) are
-- available
explain (costs off) select * from mc2p t1, lateral (select count(*) from mc3p t2 where t2.c = t1.b and abs(t2.b) = 1 and t2.a = 1) s where t1.a = 1;
- QUERY PLAN
------------------------------------------------------------------------
- Nested Loop
- -> Append
- -> Seq Scan on mc2p1 t1_1
- Filter: (a = 1)
- -> Seq Scan on mc2p2 t1_2
- Filter: (a = 1)
- -> Seq Scan on mc2p_default t1_3
- Filter: (a = 1)
- -> Aggregate
- -> Append
- -> Seq Scan on mc3p0 t2_1
- Filter: ((c = t1.b) AND (a = 1) AND (abs(b) = 1))
- -> Seq Scan on mc3p1 t2_2
- Filter: ((c = t1.b) AND (a = 1) AND (abs(b) = 1))
- -> Seq Scan on mc3p_default t2_3
- Filter: ((c = t1.b) AND (a = 1) AND (abs(b) = 1))
-(16 rows)
+ QUERY PLAN
+-----------------------------------------------------------------------------
+ Gather
+ Workers Planned: 2
+ -> Nested Loop
+ -> Parallel Append
+ -> Parallel Seq Scan on mc2p1 t1_1
+ Filter: (a = 1)
+ -> Parallel Seq Scan on mc2p2 t1_2
+ Filter: (a = 1)
+ -> Parallel Seq Scan on mc2p_default t1_3
+ Filter: (a = 1)
+ -> Aggregate
+ -> Append
+ -> Seq Scan on mc3p0 t2_1
+ Filter: ((c = t1.b) AND (a = 1) AND (abs(b) = 1))
+ -> Seq Scan on mc3p1 t2_2
+ Filter: ((c = t1.b) AND (a = 1) AND (abs(b) = 1))
+ -> Seq Scan on mc3p_default t2_3
+ Filter: ((c = t1.b) AND (a = 1) AND (abs(b) = 1))
+(18 rows)
-- also here, because values for all keys are provided
explain (costs off) select * from mc2p t1, lateral (select count(*) from mc3p t2 where t2.a = 1 and abs(t2.b) = 1 and t2.c = 1) s where t1.a = 1;
diff --git a/src/test/regress/expected/select_parallel.out b/src/test/regress/expected/select_parallel.out
index 9b4d7dd44a..01443e2ffb 100644
--- a/src/test/regress/expected/select_parallel.out
+++ b/src/test/regress/expected/select_parallel.out
@@ -137,8 +137,8 @@ create table part_pa_test_p2 partition of part_pa_test for values from (0) to (m
explain (costs off)
select (select max((select pa1.b from part_pa_test pa1 where pa1.a = pa2.a)))
from part_pa_test pa2;
- QUERY PLAN
---------------------------------------------------------------
+ QUERY PLAN
+----------------------------------------------------------------
Aggregate
-> Gather
Workers Planned: 3
@@ -148,12 +148,14 @@ explain (costs off)
SubPlan 2
-> Result
SubPlan 1
- -> Append
- -> Seq Scan on part_pa_test_p1 pa1_1
- Filter: (a = pa2.a)
- -> Seq Scan on part_pa_test_p2 pa1_2
- Filter: (a = pa2.a)
-(14 rows)
+ -> Gather
+ Workers Planned: 3
+ -> Parallel Append
+ -> Parallel Seq Scan on part_pa_test_p1 pa1_1
+ Filter: (a = pa2.a)
+ -> Parallel Seq Scan on part_pa_test_p2 pa1_2
+ Filter: (a = pa2.a)
+(16 rows)
drop table part_pa_test;
-- test with leader participation disabled
@@ -320,19 +322,19 @@ explain (costs off, verbose) select
QUERY PLAN
----------------------------------------------------------------------------
Gather
- Output: (SubPlan 1)
+ Output: ((SubPlan 1))
Workers Planned: 4
-> Nested Loop
- Output: t.unique1
+ Output: (SubPlan 1)
-> Parallel Index Only Scan using tenk1_unique1 on public.tenk1 t
Output: t.unique1
-> Function Scan on pg_catalog.generate_series
Output: generate_series.generate_series
Function Call: generate_series(1, 10)
- SubPlan 1
- -> Index Only Scan using tenk1_unique1 on public.tenk1
- Output: t.unique1
- Index Cond: (tenk1.unique1 = t.unique1)
+ SubPlan 1
+ -> Index Only Scan using tenk1_unique1 on public.tenk1
+ Output: t.unique1
+ Index Cond: (tenk1.unique1 = t.unique1)
(14 rows)
explain (costs off, verbose) select
@@ -341,63 +343,69 @@ explain (costs off, verbose) select
QUERY PLAN
----------------------------------------------------------------------
Gather
- Output: (SubPlan 1)
+ Output: ((SubPlan 1))
Workers Planned: 4
-> Parallel Index Only Scan using tenk1_unique1 on public.tenk1 t
- Output: t.unique1
- SubPlan 1
- -> Index Only Scan using tenk1_unique1 on public.tenk1
- Output: t.unique1
- Index Cond: (tenk1.unique1 = t.unique1)
+ Output: (SubPlan 1)
+ SubPlan 1
+ -> Index Only Scan using tenk1_unique1 on public.tenk1
+ Output: t.unique1
+ Index Cond: (tenk1.unique1 = t.unique1)
(9 rows)
explain (costs off, verbose) select
(select t.unique1 from tenk1 where tenk1.unique1 = t.unique1)
from tenk1 t
limit 1;
- QUERY PLAN
--------------------------------------------------------------------
+ QUERY PLAN
+----------------------------------------------------------------------------
Limit
Output: ((SubPlan 1))
- -> Seq Scan on public.tenk1 t
- Output: (SubPlan 1)
- SubPlan 1
- -> Index Only Scan using tenk1_unique1 on public.tenk1
- Output: t.unique1
- Index Cond: (tenk1.unique1 = t.unique1)
-(8 rows)
+ -> Gather
+ Output: ((SubPlan 1))
+ Workers Planned: 4
+ -> Parallel Index Only Scan using tenk1_unique1 on public.tenk1 t
+ Output: (SubPlan 1)
+ SubPlan 1
+ -> Index Only Scan using tenk1_unique1 on public.tenk1
+ Output: t.unique1
+ Index Cond: (tenk1.unique1 = t.unique1)
+(11 rows)
explain (costs off, verbose) select t.unique1
from tenk1 t
where t.unique1 = (select t.unique1 from tenk1 where tenk1.unique1 = t.unique1);
- QUERY PLAN
--------------------------------------------------------------
- Seq Scan on public.tenk1 t
+ QUERY PLAN
+----------------------------------------------------------------------
+ Gather
Output: t.unique1
- Filter: (t.unique1 = (SubPlan 1))
- SubPlan 1
- -> Index Only Scan using tenk1_unique1 on public.tenk1
- Output: t.unique1
- Index Cond: (tenk1.unique1 = t.unique1)
-(7 rows)
+ Workers Planned: 4
+ -> Parallel Index Only Scan using tenk1_unique1 on public.tenk1 t
+ Output: t.unique1
+ Filter: (t.unique1 = (SubPlan 1))
+ SubPlan 1
+ -> Index Only Scan using tenk1_unique1 on public.tenk1
+ Output: t.unique1
+ Index Cond: (tenk1.unique1 = t.unique1)
+(10 rows)
explain (costs off, verbose) select *
from tenk1 t
order by (select t.unique1 from tenk1 where tenk1.unique1 = t.unique1);
- QUERY PLAN
-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
- Sort
+ QUERY PLAN
+----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
+ Gather Merge
Output: t.unique1, t.unique2, t.two, t.four, t.ten, t.twenty, t.hundred, t.thousand, t.twothousand, t.fivethous, t.tenthous, t.odd, t.even, t.stringu1, t.stringu2, t.string4, ((SubPlan 1))
- Sort Key: ((SubPlan 1))
- -> Gather
- Output: t.unique1, t.unique2, t.two, t.four, t.ten, t.twenty, t.hundred, t.thousand, t.twothousand, t.fivethous, t.tenthous, t.odd, t.even, t.stringu1, t.stringu2, t.string4, (SubPlan 1)
- Workers Planned: 4
+ Workers Planned: 4
+ -> Sort
+ Output: t.unique1, t.unique2, t.two, t.four, t.ten, t.twenty, t.hundred, t.thousand, t.twothousand, t.fivethous, t.tenthous, t.odd, t.even, t.stringu1, t.stringu2, t.string4, ((SubPlan 1))
+ Sort Key: ((SubPlan 1))
-> Parallel Seq Scan on public.tenk1 t
- Output: t.unique1, t.unique2, t.two, t.four, t.ten, t.twenty, t.hundred, t.thousand, t.twothousand, t.fivethous, t.tenthous, t.odd, t.even, t.stringu1, t.stringu2, t.string4
- SubPlan 1
- -> Index Only Scan using tenk1_unique1 on public.tenk1
- Output: t.unique1
- Index Cond: (tenk1.unique1 = t.unique1)
+ Output: t.unique1, t.unique2, t.two, t.four, t.ten, t.twenty, t.hundred, t.thousand, t.twothousand, t.fivethous, t.tenthous, t.odd, t.even, t.stringu1, t.stringu2, t.string4, (SubPlan 1)
+ SubPlan 1
+ -> Index Only Scan using tenk1_unique1 on public.tenk1
+ Output: t.unique1
+ Index Cond: (tenk1.unique1 = t.unique1)
(12 rows)
-- test subplan in join/lateral join
@@ -409,14 +417,14 @@ explain (costs off, verbose, timing off) select t.unique1, l.*
QUERY PLAN
----------------------------------------------------------------------
Gather
- Output: t.unique1, (SubPlan 1)
+ Output: t.unique1, ((SubPlan 1))
Workers Planned: 4
-> Parallel Index Only Scan using tenk1_unique1 on public.tenk1 t
- Output: t.unique1
- SubPlan 1
- -> Index Only Scan using tenk1_unique1 on public.tenk1
- Output: t.unique1
- Index Cond: (tenk1.unique1 = t.unique1)
+ Output: t.unique1, (SubPlan 1)
+ SubPlan 1
+ -> Index Only Scan using tenk1_unique1 on public.tenk1
+ Output: t.unique1
+ Index Cond: (tenk1.unique1 = t.unique1)
(9 rows)
-- this is not parallel-safe due to use of random() within SubLink's testexpr:
@@ -1322,8 +1330,10 @@ SELECT 1 FROM tenk1_vw_sec
-> Parallel Index Only Scan using tenk1_unique1 on tenk1
SubPlan 1
-> Aggregate
- -> Seq Scan on int4_tbl
- Filter: (f1 < tenk1_vw_sec.unique1)
-(9 rows)
+ -> Gather
+ Workers Planned: 1
+ -> Parallel Seq Scan on int4_tbl
+ Filter: (f1 < tenk1_vw_sec.unique1)
+(11 rows)
rollback;
--
2.32.1 (Apple Git-133)
^ permalink raw reply [nested|flat] 35+ messages in thread
* [PATCH 1/4] f!fixes for LZ4
@ 2023-02-24 20:07 Justin Pryzby <[email protected]>
0 siblings, 0 replies; 35+ messages in thread
From: Justin Pryzby @ 2023-02-24 20:07 UTC (permalink / raw)
---
src/bin/pg_dump/compress_gzip.c | 8 --------
src/bin/pg_dump/compress_io.h | 2 +-
src/bin/pg_dump/compress_lz4.c | 12 ++++--------
src/bin/pg_dump/pg_dump.c | 2 --
4 files changed, 5 insertions(+), 19 deletions(-)
diff --git a/src/bin/pg_dump/compress_gzip.c b/src/bin/pg_dump/compress_gzip.c
index 0af65afeb4e..52f41c2e58c 100644
--- a/src/bin/pg_dump/compress_gzip.c
+++ b/src/bin/pg_dump/compress_gzip.c
@@ -123,17 +123,9 @@ WriteDataToArchiveGzip(ArchiveHandle *AH, CompressorState *cs,
gzipcs->outbuf = pg_malloc(ZLIB_OUT_SIZE + 1);
gzipcs->outsize = ZLIB_OUT_SIZE;
- /*
- * A level of zero simply copies the input one block at the time. This
- * is probably not what the user wanted when calling this interface.
- */
- if (cs->compression_spec.level == 0)
- pg_fatal("requested to compress the archive yet no level was specified");
-
if (deflateInit(zp, cs->compression_spec.level) != Z_OK)
pg_fatal("could not initialize compression library: %s", zp->msg);
- /* Just be paranoid - maybe End is called after Start, with no Write */
zp->next_out = gzipcs->outbuf;
zp->avail_out = gzipcs->outsize;
}
diff --git a/src/bin/pg_dump/compress_io.h b/src/bin/pg_dump/compress_io.h
index bbde2693915..cdb15951ea9 100644
--- a/src/bin/pg_dump/compress_io.h
+++ b/src/bin/pg_dump/compress_io.h
@@ -172,7 +172,7 @@ struct CompressFileHandle
extern CompressFileHandle *InitCompressFileHandle(const pg_compress_specification compression_spec);
/*
- * Initialize a compress file stream. Deffer the compression algorithm
+ * Initialize a compress file stream. Infer the compression algorithm
* from 'path', either by examining its suffix or by appending the supported
* suffixes in 'path'.
*/
diff --git a/src/bin/pg_dump/compress_lz4.c b/src/bin/pg_dump/compress_lz4.c
index fe1014e6e77..7dacfeae469 100644
--- a/src/bin/pg_dump/compress_lz4.c
+++ b/src/bin/pg_dump/compress_lz4.c
@@ -105,12 +105,8 @@ EndCompressorLZ4(ArchiveHandle *AH, CompressorState *cs)
LZ4CompressorState *LZ4cs;
LZ4cs = (LZ4CompressorState *) cs->private_data;
- if (LZ4cs)
- {
- pg_free(LZ4cs->outbuf);
- pg_free(LZ4cs);
- cs->private_data = NULL;
- }
+ pg_free(LZ4cs->outbuf);
+ pg_free(LZ4cs);
}
@@ -161,8 +157,8 @@ typedef struct LZ4File
} LZ4File;
/*
- * LZ4 equivalent to feof() or gzeof(). The end of file is reached if there
- * is no decompressed output in the overflow buffer and the end of the file
+ * LZ4 equivalent to feof() or gzeof(). Return true iff there is no
+ * decompressed output in the overflow buffer and the end of the backing file
* is reached.
*/
static int
diff --git a/src/bin/pg_dump/pg_dump.c b/src/bin/pg_dump/pg_dump.c
index 24ba936332d..ce2242195f3 100644
--- a/src/bin/pg_dump/pg_dump.c
+++ b/src/bin/pg_dump/pg_dump.c
@@ -733,8 +733,6 @@ main(int argc, char **argv)
#ifdef HAVE_LIBZ
parse_compress_specification(PG_COMPRESSION_GZIP, NULL,
&compression_spec);
-#else
- /* Nothing to do in the default case */
#endif
}
--
2.34.1
--Fw50BJRL4GwAnGn1
Content-Type: text/x-diff; charset=us-ascii
Content-Disposition: attachment;
filename="0002-f-fixes-for-LZ4-which-also-conflict-with-the-ZSTD-pa.patch"
^ permalink raw reply [nested|flat] 35+ messages in thread
* Re: Parallelize correlated subqueries that execute within each worker
@ 2023-03-08 18:07 Antonin Houska <[email protected]>
parent: James Coleman <[email protected]>
0 siblings, 0 replies; 35+ messages in thread
From: Antonin Houska @ 2023-03-08 18:07 UTC (permalink / raw)
To: James Coleman <[email protected]>; +Cc: Tomas Vondra <[email protected]>; vignesh C <[email protected]>; Andres Freund <[email protected]>; Robert Haas <[email protected]>; pgsql-hackers; Amit Kapila <[email protected]>; Tom Lane <[email protected]>
James Coleman <[email protected]> wrote:
> On Mon, Feb 6, 2023 at 11:39 AM Antonin Houska <[email protected]> wrote:
> Attached is v9.
ok, I've changed the status to RfC
--
Antonin Houska
Web: https://www.cybertec-postgresql.com
^ permalink raw reply [nested|flat] 35+ messages in thread
* Re: Parallelize correlated subqueries that execute within each worker
@ 2023-06-06 09:35 Richard Guo <[email protected]>
parent: James Coleman <[email protected]>
1 sibling, 1 reply; 35+ messages in thread
From: Richard Guo @ 2023-06-06 09:35 UTC (permalink / raw)
To: James Coleman <[email protected]>; +Cc: Tomas Vondra <[email protected]>; vignesh C <[email protected]>; Andres Freund <[email protected]>; Robert Haas <[email protected]>; pgsql-hackers; Amit Kapila <[email protected]>; Tom Lane <[email protected]>
On Mon, Jan 23, 2023 at 10:00 PM James Coleman <[email protected]> wrote:
> Which this patch we do in fact now see (as expected) rels with
> non-empty lateral_relids showing up in generate_[useful_]gather_paths.
> And the partial paths can now have non-empty required outer rels. I'm
> not able to come up with a plan that would actually be caught by those
> checks; I theorize that because of the few places we actually call
> generate_[useful_]gather_paths we are in practice already excluding
> those, but for now I've left these as a conditional rather than an
> assertion because it seems like the kind of guard we'd want to ensure
> those methods are safe.
I'm trying to understand this part. AFAICS we will not create partial
paths for a rel, base or join, if it has lateral references. So it
seems to me that in generate_[useful_]gather_paths after we've checked
that there are partial paths, the checks for lateral_relids are not
necessary because lateral_relids should always be empty in this case.
Maybe I'm missing something.
And while trying the v9 patch I came across a crash with the query
below.
set min_parallel_table_scan_size to 0;
set parallel_setup_cost to 0;
set parallel_tuple_cost to 0;
explain (costs off)
select * from pg_description t1 where objoid in
(select objoid from pg_description t2 where t2.description =
t1.description);
QUERY PLAN
--------------------------------------------------------
Seq Scan on pg_description t1
Filter: (SubPlan 1)
SubPlan 1
-> Gather
Workers Planned: 2
-> Parallel Seq Scan on pg_description t2
Filter: (description = t1.description)
(7 rows)
select * from pg_description t1 where objoid in
(select objoid from pg_description t2 where t2.description =
t1.description);
WARNING: terminating connection because of crash of another server process
Seems something is wrong when extracting the argument from the Param in
parallel worker.
BTW another rebase is needed as it no longer applies to HEAD.
Thanks
Richard
^ permalink raw reply [nested|flat] 35+ messages in thread
* Re: Parallelize correlated subqueries that execute within each worker
@ 2023-06-12 02:23 James Coleman <[email protected]>
parent: Richard Guo <[email protected]>
0 siblings, 2 replies; 35+ messages in thread
From: James Coleman @ 2023-06-12 02:23 UTC (permalink / raw)
To: Richard Guo <[email protected]>; +Cc: Tomas Vondra <[email protected]>; vignesh C <[email protected]>; Andres Freund <[email protected]>; Robert Haas <[email protected]>; pgsql-hackers; Amit Kapila <[email protected]>; Tom Lane <[email protected]>
On Tue, Jun 6, 2023 at 4:36 AM Richard Guo <[email protected]> wrote:
>
>
> On Mon, Jan 23, 2023 at 10:00 PM James Coleman <[email protected]> wrote:
>>
>> Which this patch we do in fact now see (as expected) rels with
>> non-empty lateral_relids showing up in generate_[useful_]gather_paths.
>> And the partial paths can now have non-empty required outer rels. I'm
>> not able to come up with a plan that would actually be caught by those
>> checks; I theorize that because of the few places we actually call
>> generate_[useful_]gather_paths we are in practice already excluding
>> those, but for now I've left these as a conditional rather than an
>> assertion because it seems like the kind of guard we'd want to ensure
>> those methods are safe.
>
>
> I'm trying to understand this part. AFAICS we will not create partial
> paths for a rel, base or join, if it has lateral references. So it
> seems to me that in generate_[useful_]gather_paths after we've checked
> that there are partial paths, the checks for lateral_relids are not
> necessary because lateral_relids should always be empty in this case.
> Maybe I'm missing something.
At first I was thinking "isn't the point of the patch to generate
partial paths for rels with lateral references" given what I'd written
back in January, but I added "Assert(bms_is_empty(required_outer));"
to both of those functions and the assertion never fails running the
tests (including my newly parallelizable queries). I'm almost positive
I'd checked this back in January (not only had I'd explicitly written
that I'd confirmed we had non-empty lateral_relids there, but also it
was the entire based of the alternate approach to the patch), but...I
can't go back to 5 months ago and remember what I'd done.
Ah! Your comment about "after we've checked that there are partial
paths" triggered a thought. I think originally I'd had the
"bms_is_subset(required_outer, rel->relids)" check first in these
functions. And indeed if I run the tests with that the assertion moved
to above the partial paths check, I get failures in
generate_useful_gather_paths specifically. Mystery solved!
> And while trying the v9 patch I came across a crash with the query
> below.
>
> set min_parallel_table_scan_size to 0;
> set parallel_setup_cost to 0;
> set parallel_tuple_cost to 0;
>
> explain (costs off)
> select * from pg_description t1 where objoid in
> (select objoid from pg_description t2 where t2.description = t1.description);
> QUERY PLAN
> --------------------------------------------------------
> Seq Scan on pg_description t1
> Filter: (SubPlan 1)
> SubPlan 1
> -> Gather
> Workers Planned: 2
> -> Parallel Seq Scan on pg_description t2
> Filter: (description = t1.description)
> (7 rows)
>
> select * from pg_description t1 where objoid in
> (select objoid from pg_description t2 where t2.description = t1.description);
> WARNING: terminating connection because of crash of another server process
>
> Seems something is wrong when extracting the argument from the Param in
> parallel worker.
With what I'm trying to change I don't think this plan should ever be
generated since it means we'd have to pass a param from the outer seq
scan into the parallel subplan, which we can't do (currently).
I've attached the full backtrace to the email, but as you hinted at
the parallel worker is trying to get the param (in this case
detoasting it), but the param doesn't exist on the worker, so it seg
faults. Looking at this further I think there's an existing test case
that exposes the misplanning here (the one right under the comment
"Parallel Append is not to be used when the subpath depends on the
outer param" in select_parallel.sql), but it doesn't seg fault because
the param is an integer, doesn't need to be detoasted, and therefore
(I think) we skate by (but probably with wrong results in depending on
the dataset).
Interestingly this is one of the existing test queries my original
patch approach didn't change, so this gives me something specific to
work with improving the path. Thanks for testing this and bringing
this to my attention!
BTW are you by any chance testing on ARM macOS? I reproduced the issue
there, but for some reason I did not reproduce the error (and the plan
wasn't parallelized) when I tested this on linux. Perhaps I missed
setting something up; it seems odd.
> BTW another rebase is needed as it no longer applies to HEAD.
Apologies; I'd rebased, but hadn't updated the thread. See attached
for an updated series (albeit still broken on your test query).
Thanks,
James
* thread #1, queue = 'com.apple.main-thread', stop reason = EXC_BAD_ACCESS (code=1, address=0x0)
* frame #0: 0x000000010449cab0 postgres`toast_raw_datum_size(value=0) at detoast.c:550:6
frame #1: 0x0000000104cf9438 postgres`texteq(fcinfo=0x0000000112809c80) at varlena.c:1645:10
frame #2: 0x00000001047ca7ac postgres`ExecInterpExpr(state=0x00000001128097e0, econtext=0x0000000112808c48, isnull=0x000000016b97e39f) at execExprInterp.c:758:8
frame #3: 0x00000001047c98bc postgres`ExecInterpExprStillValid(state=0x00000001128097e0, econtext=0x0000000112808c48, isNull=0x000000016b97e39f) at execExprInterp.c:1870:9
frame #4: 0x00000001047ee1b0 postgres`ExecEvalExprSwitchContext(state=0x00000001128097e0, econtext=0x0000000112808c48, isNull=0x000000016b97e39f) at executor.h:355:13
frame #5: 0x00000001047edddc postgres`ExecQual(state=0x00000001128097e0, econtext=0x0000000112808c48) at executor.h:424:8
frame #6: 0x00000001047ed964 postgres`ExecScan(node=0x0000000112808d68, accessMtd=(postgres`SeqNext at nodeSeqscan.c:51), recheckMtd=(postgres`SeqRecheck at nodeSeqscan.c:90)) at exec
Scan.c:226:23
frame #7: 0x0000000104837ea8 postgres`ExecSeqScan(pstate=0x0000000112808d68) at nodeSeqscan.c:112:9
frame #8: 0x00000001047e8ca0 postgres`ExecProcNodeFirst(node=0x0000000112808d68) at execProcnode.c:464:9
frame #9: 0x00000001047dfd90 postgres`ExecProcNode(node=0x0000000112808d68) at executor.h:273:9
frame #10: 0x00000001047daa28 postgres`ExecutePlan(estate=0x0000000112808318, planstate=0x0000000112808d68, use_parallel_mode=false, operation=CMD_SELECT, sendTuples=true, numberTuple
s=0, direction=ForwardScanDirection, dest=0x00000001130389d8, execute_once=true) at execMain.c:1661:10
frame #11: 0x00000001047da8d4 postgres`standard_ExecutorRun(queryDesc=0x0000000113039738, direction=ForwardScanDirection, count=0, execute_once=true) at execMain.c:365:3
frame #12: 0x00000001047da644 postgres`ExecutorRun(queryDesc=0x0000000113039738, direction=ForwardScanDirection, count=0, execute_once=true) at execMain.c:309:3
frame #13: 0x00000001047e3230 postgres`ParallelQueryMain(seg=0x000000011300a5b8, toc=0x0000000105434000) at execParallel.c:1464:2
frame #14: 0x000000010458a8d0 postgres`ParallelWorkerMain(main_arg=4065634722) at parallel.c:1521:2
frame #15: 0x00000001049e70e4 postgres`StartBackgroundWorker at bgworker.c:861:2
frame #16: 0x00000001049f64b8 postgres`do_start_bgworker(rw=0x0000000113804080) at postmaster.c:5762:4
frame #17: 0x00000001049eed90 postgres`maybe_start_bgworkers at postmaster.c:5986:9
frame #18: 0x00000001049f1764 postgres`process_pm_pmsignal at postmaster.c:5149:3
frame #19: 0x00000001049eef7c postgres`ServerLoop at postmaster.c:1770:5
frame #20: 0x00000001049edb48 postgres`PostmasterMain(argc=3, argv=0x00006000016453c0) at postmaster.c:1463:11
frame #21: 0x00000001048782f4 postgres`main(argc=3, argv=0x00006000016453c0) at main.c:198:3
frame #22: 0x00000001a08cff28 dyld`start + 2236
Attachments:
[text/plain] backtrace.txt (2.9K, ../../CAAaqYe-_TObm5KwmZLYXBJ3BJGh4cUZWM0v1mY1gWTMkRNQXDQ@mail.gmail.com/2-backtrace.txt)
download | inline:
* thread #1, queue = 'com.apple.main-thread', stop reason = EXC_BAD_ACCESS (code=1, address=0x0)
* frame #0: 0x000000010449cab0 postgres`toast_raw_datum_size(value=0) at detoast.c:550:6
frame #1: 0x0000000104cf9438 postgres`texteq(fcinfo=0x0000000112809c80) at varlena.c:1645:10
frame #2: 0x00000001047ca7ac postgres`ExecInterpExpr(state=0x00000001128097e0, econtext=0x0000000112808c48, isnull=0x000000016b97e39f) at execExprInterp.c:758:8
frame #3: 0x00000001047c98bc postgres`ExecInterpExprStillValid(state=0x00000001128097e0, econtext=0x0000000112808c48, isNull=0x000000016b97e39f) at execExprInterp.c:1870:9
frame #4: 0x00000001047ee1b0 postgres`ExecEvalExprSwitchContext(state=0x00000001128097e0, econtext=0x0000000112808c48, isNull=0x000000016b97e39f) at executor.h:355:13
frame #5: 0x00000001047edddc postgres`ExecQual(state=0x00000001128097e0, econtext=0x0000000112808c48) at executor.h:424:8
frame #6: 0x00000001047ed964 postgres`ExecScan(node=0x0000000112808d68, accessMtd=(postgres`SeqNext at nodeSeqscan.c:51), recheckMtd=(postgres`SeqRecheck at nodeSeqscan.c:90)) at exec
Scan.c:226:23
frame #7: 0x0000000104837ea8 postgres`ExecSeqScan(pstate=0x0000000112808d68) at nodeSeqscan.c:112:9
frame #8: 0x00000001047e8ca0 postgres`ExecProcNodeFirst(node=0x0000000112808d68) at execProcnode.c:464:9
frame #9: 0x00000001047dfd90 postgres`ExecProcNode(node=0x0000000112808d68) at executor.h:273:9
frame #10: 0x00000001047daa28 postgres`ExecutePlan(estate=0x0000000112808318, planstate=0x0000000112808d68, use_parallel_mode=false, operation=CMD_SELECT, sendTuples=true, numberTuple
s=0, direction=ForwardScanDirection, dest=0x00000001130389d8, execute_once=true) at execMain.c:1661:10
frame #11: 0x00000001047da8d4 postgres`standard_ExecutorRun(queryDesc=0x0000000113039738, direction=ForwardScanDirection, count=0, execute_once=true) at execMain.c:365:3
frame #12: 0x00000001047da644 postgres`ExecutorRun(queryDesc=0x0000000113039738, direction=ForwardScanDirection, count=0, execute_once=true) at execMain.c:309:3
frame #13: 0x00000001047e3230 postgres`ParallelQueryMain(seg=0x000000011300a5b8, toc=0x0000000105434000) at execParallel.c:1464:2
frame #14: 0x000000010458a8d0 postgres`ParallelWorkerMain(main_arg=4065634722) at parallel.c:1521:2
frame #15: 0x00000001049e70e4 postgres`StartBackgroundWorker at bgworker.c:861:2
frame #16: 0x00000001049f64b8 postgres`do_start_bgworker(rw=0x0000000113804080) at postmaster.c:5762:4
frame #17: 0x00000001049eed90 postgres`maybe_start_bgworkers at postmaster.c:5986:9
frame #18: 0x00000001049f1764 postgres`process_pm_pmsignal at postmaster.c:5149:3
frame #19: 0x00000001049eef7c postgres`ServerLoop at postmaster.c:1770:5
frame #20: 0x00000001049edb48 postgres`PostmasterMain(argc=3, argv=0x00006000016453c0) at postmaster.c:1463:11
frame #21: 0x00000001048782f4 postgres`main(argc=3, argv=0x00006000016453c0) at main.c:198:3
frame #22: 0x00000001a08cff28 dyld`start + 2236
[application/octet-stream] v10-0001-Add-tests-before-change.patch (7.2K, ../../CAAaqYe-_TObm5KwmZLYXBJ3BJGh4cUZWM0v1mY1gWTMkRNQXDQ@mail.gmail.com/3-v10-0001-Add-tests-before-change.patch)
download | inline diff:
From 59c67d670e024173e8417867cd15d7edc257f012 Mon Sep 17 00:00:00 2001
From: jcoleman <[email protected]>
Date: Mon, 26 Sep 2022 20:30:23 -0400
Subject: [PATCH v10 1/2] Add tests before change
---
src/test/regress/expected/select_parallel.out | 108 ++++++++++++++++++
src/test/regress/sql/select_parallel.sql | 25 ++++
2 files changed, 133 insertions(+)
diff --git a/src/test/regress/expected/select_parallel.out b/src/test/regress/expected/select_parallel.out
index d88353d496..04810d2756 100644
--- a/src/test/regress/expected/select_parallel.out
+++ b/src/test/regress/expected/select_parallel.out
@@ -311,6 +311,114 @@ select count(*) from tenk1 where (two, four) not in
10000
(1 row)
+-- test parallel plans for queries containing correlated subplans
+-- where the subplan only needs params available from the current
+-- worker's scan.
+explain (costs off, verbose) select
+ (select t.unique1 from tenk1 where tenk1.unique1 = t.unique1)
+ from tenk1 t, generate_series(1, 10);
+ QUERY PLAN
+----------------------------------------------------------------------------
+ Gather
+ Output: (SubPlan 1)
+ Workers Planned: 4
+ -> Nested Loop
+ Output: t.unique1
+ -> Parallel Index Only Scan using tenk1_unique1 on public.tenk1 t
+ Output: t.unique1
+ -> Function Scan on pg_catalog.generate_series
+ Output: generate_series.generate_series
+ Function Call: generate_series(1, 10)
+ SubPlan 1
+ -> Index Only Scan using tenk1_unique1 on public.tenk1
+ Output: t.unique1
+ Index Cond: (tenk1.unique1 = t.unique1)
+(14 rows)
+
+explain (costs off, verbose) select
+ (select t.unique1 from tenk1 where tenk1.unique1 = t.unique1)
+ from tenk1 t;
+ QUERY PLAN
+----------------------------------------------------------------------
+ Gather
+ Output: (SubPlan 1)
+ Workers Planned: 4
+ -> Parallel Index Only Scan using tenk1_unique1 on public.tenk1 t
+ Output: t.unique1
+ SubPlan 1
+ -> Index Only Scan using tenk1_unique1 on public.tenk1
+ Output: t.unique1
+ Index Cond: (tenk1.unique1 = t.unique1)
+(9 rows)
+
+explain (costs off, verbose) select
+ (select t.unique1 from tenk1 where tenk1.unique1 = t.unique1)
+ from tenk1 t
+ limit 1;
+ QUERY PLAN
+-------------------------------------------------------------------
+ Limit
+ Output: ((SubPlan 1))
+ -> Seq Scan on public.tenk1 t
+ Output: (SubPlan 1)
+ SubPlan 1
+ -> Index Only Scan using tenk1_unique1 on public.tenk1
+ Output: t.unique1
+ Index Cond: (tenk1.unique1 = t.unique1)
+(8 rows)
+
+explain (costs off, verbose) select t.unique1
+ from tenk1 t
+ where t.unique1 = (select t.unique1 from tenk1 where tenk1.unique1 = t.unique1);
+ QUERY PLAN
+-------------------------------------------------------------
+ Seq Scan on public.tenk1 t
+ Output: t.unique1
+ Filter: (t.unique1 = (SubPlan 1))
+ SubPlan 1
+ -> Index Only Scan using tenk1_unique1 on public.tenk1
+ Output: t.unique1
+ Index Cond: (tenk1.unique1 = t.unique1)
+(7 rows)
+
+explain (costs off, verbose) select *
+ from tenk1 t
+ order by (select t.unique1 from tenk1 where tenk1.unique1 = t.unique1);
+ QUERY PLAN
+----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
+ Sort
+ Output: t.unique1, t.unique2, t.two, t.four, t.ten, t.twenty, t.hundred, t.thousand, t.twothousand, t.fivethous, t.tenthous, t.odd, t.even, t.stringu1, t.stringu2, t.string4, ((SubPlan 1))
+ Sort Key: ((SubPlan 1))
+ -> Gather
+ Output: t.unique1, t.unique2, t.two, t.four, t.ten, t.twenty, t.hundred, t.thousand, t.twothousand, t.fivethous, t.tenthous, t.odd, t.even, t.stringu1, t.stringu2, t.string4, (SubPlan 1)
+ Workers Planned: 4
+ -> Parallel Seq Scan on public.tenk1 t
+ Output: t.unique1, t.unique2, t.two, t.four, t.ten, t.twenty, t.hundred, t.thousand, t.twothousand, t.fivethous, t.tenthous, t.odd, t.even, t.stringu1, t.stringu2, t.string4
+ SubPlan 1
+ -> Index Only Scan using tenk1_unique1 on public.tenk1
+ Output: t.unique1
+ Index Cond: (tenk1.unique1 = t.unique1)
+(12 rows)
+
+-- test subplan in join/lateral join
+explain (costs off, verbose, timing off) select t.unique1, l.*
+ from tenk1 t
+ join lateral (
+ select (select t.unique1 from tenk1 where tenk1.unique1 = t.unique1 offset 0)
+ ) l on true;
+ QUERY PLAN
+----------------------------------------------------------------------
+ Gather
+ Output: t.unique1, (SubPlan 1)
+ Workers Planned: 4
+ -> Parallel Index Only Scan using tenk1_unique1 on public.tenk1 t
+ Output: t.unique1
+ SubPlan 1
+ -> Index Only Scan using tenk1_unique1 on public.tenk1
+ Output: t.unique1
+ Index Cond: (tenk1.unique1 = t.unique1)
+(9 rows)
+
-- this is not parallel-safe due to use of random() within SubLink's testexpr:
explain (costs off)
select * from tenk1 where (unique1 + random())::integer not in
diff --git a/src/test/regress/sql/select_parallel.sql b/src/test/regress/sql/select_parallel.sql
index 80c914dc02..fd968285c1 100644
--- a/src/test/regress/sql/select_parallel.sql
+++ b/src/test/regress/sql/select_parallel.sql
@@ -111,6 +111,31 @@ explain (costs off)
(select hundred, thousand from tenk2 where thousand > 100);
select count(*) from tenk1 where (two, four) not in
(select hundred, thousand from tenk2 where thousand > 100);
+-- test parallel plans for queries containing correlated subplans
+-- where the subplan only needs params available from the current
+-- worker's scan.
+explain (costs off, verbose) select
+ (select t.unique1 from tenk1 where tenk1.unique1 = t.unique1)
+ from tenk1 t, generate_series(1, 10);
+explain (costs off, verbose) select
+ (select t.unique1 from tenk1 where tenk1.unique1 = t.unique1)
+ from tenk1 t;
+explain (costs off, verbose) select
+ (select t.unique1 from tenk1 where tenk1.unique1 = t.unique1)
+ from tenk1 t
+ limit 1;
+explain (costs off, verbose) select t.unique1
+ from tenk1 t
+ where t.unique1 = (select t.unique1 from tenk1 where tenk1.unique1 = t.unique1);
+explain (costs off, verbose) select *
+ from tenk1 t
+ order by (select t.unique1 from tenk1 where tenk1.unique1 = t.unique1);
+-- test subplan in join/lateral join
+explain (costs off, verbose, timing off) select t.unique1, l.*
+ from tenk1 t
+ join lateral (
+ select (select t.unique1 from tenk1 where tenk1.unique1 = t.unique1 offset 0)
+ ) l on true;
-- this is not parallel-safe due to use of random() within SubLink's testexpr:
explain (costs off)
select * from tenk1 where (unique1 + random())::integer not in
--
2.39.2 (Apple Git-143)
[application/octet-stream] v10-0002-Parallelize-correlated-subqueries.patch (30.5K, ../../CAAaqYe-_TObm5KwmZLYXBJ3BJGh4cUZWM0v1mY1gWTMkRNQXDQ@mail.gmail.com/4-v10-0002-Parallelize-correlated-subqueries.patch)
download | inline diff:
From 8cd41d370c96e58f097a651b525fd585408f618a Mon Sep 17 00:00:00 2001
From: jcoleman <[email protected]>
Date: Wed, 18 Jan 2023 20:43:26 -0500
Subject: [PATCH v10 2/2] Parallelize correlated subqueries
When params are provided at the current query level (i.e., are generated
within a single worker and not shared across workers) we can safely
execute these in parallel.
Alternative approach using just relids subset check
---
doc/src/sgml/parallel.sgml | 3 +-
src/backend/optimizer/path/allpaths.c | 46 +++++--
src/backend/optimizer/path/joinpath.c | 10 +-
src/backend/optimizer/plan/planner.c | 8 ++
src/backend/optimizer/util/clauses.c | 74 ++++------
.../regress/expected/incremental_sort.out | 41 +++---
src/test/regress/expected/partition_prune.out | 104 +++++++-------
src/test/regress/expected/select_parallel.out | 128 ++++++++++--------
8 files changed, 222 insertions(+), 192 deletions(-)
diff --git a/doc/src/sgml/parallel.sgml b/doc/src/sgml/parallel.sgml
index 5acc9537d6..fd32572ec8 100644
--- a/doc/src/sgml/parallel.sgml
+++ b/doc/src/sgml/parallel.sgml
@@ -518,7 +518,8 @@ EXPLAIN SELECT * FROM pgbench_accounts WHERE filler LIKE '%x%';
<listitem>
<para>
- Plan nodes that reference a correlated <literal>SubPlan</literal>.
+ Plan nodes that reference a correlated <literal>SubPlan</literal> where
+ the result is shared between workers.
</para>
</listitem>
</itemizedlist>
diff --git a/src/backend/optimizer/path/allpaths.c b/src/backend/optimizer/path/allpaths.c
index 9bdc70c702..c9ccb508b4 100644
--- a/src/backend/optimizer/path/allpaths.c
+++ b/src/backend/optimizer/path/allpaths.c
@@ -3064,11 +3064,19 @@ generate_gather_paths(PlannerInfo *root, RelOptInfo *rel, bool override_rows)
ListCell *lc;
double rows;
double *rowsp = NULL;
+ Relids required_outer = rel->lateral_relids;
/* If there are no partial paths, there's nothing to do here. */
if (rel->partial_pathlist == NIL)
return;
+ /*
+ * Delay gather path creation until the level in the join tree where all
+ * params used in a worker are generated within that worker.
+ */
+ if (!bms_is_subset(required_outer, rel->relids))
+ return;
+
/* Should we override the rel's rowcount estimate? */
if (override_rows)
rowsp = &rows;
@@ -3079,12 +3087,17 @@ generate_gather_paths(PlannerInfo *root, RelOptInfo *rel, bool override_rows)
* of partial_pathlist because of the way add_partial_path works.
*/
cheapest_partial_path = linitial(rel->partial_pathlist);
- rows =
- cheapest_partial_path->rows * cheapest_partial_path->parallel_workers;
- simple_gather_path = (Path *)
- create_gather_path(root, rel, cheapest_partial_path, rel->reltarget,
- NULL, rowsp);
- add_path(rel, simple_gather_path);
+
+ /* We can't pass params to workers. */
+ if (bms_is_subset(PATH_REQ_OUTER(cheapest_partial_path), rel->relids))
+ {
+ rows =
+ cheapest_partial_path->rows * cheapest_partial_path->parallel_workers;
+ simple_gather_path = (Path *)
+ create_gather_path(root, rel, cheapest_partial_path, rel->reltarget,
+ PATH_REQ_OUTER(cheapest_partial_path), rowsp);
+ add_path(rel, simple_gather_path);
+ }
/*
* For each useful ordering, we can consider an order-preserving Gather
@@ -3098,9 +3111,14 @@ generate_gather_paths(PlannerInfo *root, RelOptInfo *rel, bool override_rows)
if (subpath->pathkeys == NIL)
continue;
+ /* We can't pass params to workers. */
+ if (!bms_is_subset(PATH_REQ_OUTER(subpath), rel->relids))
+ continue;
+
rows = subpath->rows * subpath->parallel_workers;
path = create_gather_merge_path(root, rel, subpath, rel->reltarget,
- subpath->pathkeys, NULL, rowsp);
+ subpath->pathkeys,
+ PATH_REQ_OUTER(subpath), rowsp);
add_path(rel, &path->path);
}
}
@@ -3202,11 +3220,19 @@ generate_useful_gather_paths(PlannerInfo *root, RelOptInfo *rel, bool override_r
double *rowsp = NULL;
List *useful_pathkeys_list = NIL;
Path *cheapest_partial_path = NULL;
+ Relids required_outer = rel->lateral_relids;
/* If there are no partial paths, there's nothing to do here. */
if (rel->partial_pathlist == NIL)
return;
+ /*
+ * Delay gather path creation until the level in the join tree where all
+ * params used in a worker are generated within that worker.
+ */
+ if (!bms_is_subset(required_outer, rel->relids))
+ return;
+
/* Should we override the rel's rowcount estimate? */
if (override_rows)
rowsp = &rows;
@@ -3236,6 +3262,10 @@ generate_useful_gather_paths(PlannerInfo *root, RelOptInfo *rel, bool override_r
Path *subpath = (Path *) lfirst(lc2);
GatherMergePath *path;
+ /* We can't pass params to workers. */
+ if (!bms_is_subset(PATH_REQ_OUTER(subpath), rel->relids))
+ continue;
+
is_sorted = pathkeys_count_contained_in(useful_pathkeys,
subpath->pathkeys,
&presorted_keys);
@@ -3295,7 +3325,7 @@ generate_useful_gather_paths(PlannerInfo *root, RelOptInfo *rel, bool override_r
subpath,
rel->reltarget,
subpath->pathkeys,
- NULL,
+ PATH_REQ_OUTER(subpath),
rowsp);
add_path(rel, &path->path);
diff --git a/src/backend/optimizer/path/joinpath.c b/src/backend/optimizer/path/joinpath.c
index cd80e61fd7..66d133d0ea 100644
--- a/src/backend/optimizer/path/joinpath.c
+++ b/src/backend/optimizer/path/joinpath.c
@@ -1850,10 +1850,12 @@ match_unsorted_outer(PlannerInfo *root,
* Consider partial nestloop and mergejoin plan if outerrel has any
* partial path and the joinrel is parallel-safe. However, we can't
* handle JOIN_UNIQUE_OUTER, because the outer path will be partial, and
- * therefore we won't be able to properly guarantee uniqueness. Nor can
- * we handle joins needing lateral rels, since partial paths must not be
- * parameterized. Similarly, we can't handle JOIN_FULL, JOIN_RIGHT and
- * JOIN_RIGHT_ANTI, because they can produce false null extended rows.
+ * therefore we won't be able to properly guarantee uniqueness. Similarly,
+ * we can't handle JOIN_FULL JOIN_RIGHT, and JOIN_RIGHT_ANTI, because they
+ * can produce false null extended rows.
+ *
+ * While partial paths may now be parameterized so long as all of the params
+ * can be generated wholly within a worker we punt on supporting that here.
*/
if (joinrel->consider_parallel &&
save_jointype != JOIN_UNIQUE_OUTER &&
diff --git a/src/backend/optimizer/plan/planner.c b/src/backend/optimizer/plan/planner.c
index 1e4dd27dba..2ca363df61 100644
--- a/src/backend/optimizer/plan/planner.c
+++ b/src/backend/optimizer/plan/planner.c
@@ -7353,11 +7353,16 @@ gather_grouping_paths(PlannerInfo *root, RelOptInfo *rel)
ListCell *lc;
Path *cheapest_partial_path;
+ /* By grouping time we shouldn't have any lateral dependencies. */
+ Assert(rel->lateral_relids == NULL);
+
/* Try Gather for unordered paths and Gather Merge for ordered ones. */
generate_useful_gather_paths(root, rel, true);
/* Try cheapest partial path + explicit Sort + Gather Merge. */
cheapest_partial_path = linitial(rel->partial_pathlist);
+ /* By grouping time we shouldn't have any lateral dependencies. */
+ Assert(PATH_REQ_OUTER(cheapest_partial_path) == NULL);
if (!pathkeys_contained_in(root->group_pathkeys,
cheapest_partial_path->pathkeys))
{
@@ -7409,6 +7414,9 @@ gather_grouping_paths(PlannerInfo *root, RelOptInfo *rel)
if (presorted_keys == 0)
continue;
+ /* By grouping time we shouldn't have any lateral dependencies. */
+ Assert(PATH_REQ_OUTER(path) == NULL);
+
path = (Path *) create_incremental_sort_path(root,
rel,
path,
diff --git a/src/backend/optimizer/util/clauses.c b/src/backend/optimizer/util/clauses.c
index 7f453b04f8..894b93b8c2 100644
--- a/src/backend/optimizer/util/clauses.c
+++ b/src/backend/optimizer/util/clauses.c
@@ -91,7 +91,6 @@ typedef struct
{
char max_hazard; /* worst proparallel hazard found so far */
char max_interesting; /* worst proparallel hazard of interest */
- List *safe_param_ids; /* PARAM_EXEC Param IDs to treat as safe */
} max_parallel_hazard_context;
static bool contain_agg_clause_walker(Node *node, void *context);
@@ -654,7 +653,6 @@ max_parallel_hazard(Query *parse)
context.max_hazard = PROPARALLEL_SAFE;
context.max_interesting = PROPARALLEL_UNSAFE;
- context.safe_param_ids = NIL;
(void) max_parallel_hazard_walker((Node *) parse, &context);
return context.max_hazard;
}
@@ -665,43 +663,24 @@ max_parallel_hazard(Query *parse)
*
* root->glob->maxParallelHazard must previously have been set to the
* result of max_parallel_hazard() on the whole query.
+ *
+ * The caller is responsible for verifying that PARAM_EXEC Params are generated
+ * at the current plan level.
*/
bool
is_parallel_safe(PlannerInfo *root, Node *node)
{
max_parallel_hazard_context context;
- PlannerInfo *proot;
- ListCell *l;
/*
- * Even if the original querytree contained nothing unsafe, we need to
- * search the expression if we have generated any PARAM_EXEC Params while
- * planning, because those are parallel-restricted and there might be one
- * in this expression. But otherwise we don't need to look.
+ * If we've already checked the querytree don't burn cycles doing it again.
*/
- if (root->glob->maxParallelHazard == PROPARALLEL_SAFE &&
- root->glob->paramExecTypes == NIL)
+ if (root->glob->maxParallelHazard == PROPARALLEL_SAFE)
return true;
+
/* Else use max_parallel_hazard's search logic, but stop on RESTRICTED */
context.max_hazard = PROPARALLEL_SAFE;
context.max_interesting = PROPARALLEL_RESTRICTED;
- context.safe_param_ids = NIL;
-
- /*
- * The params that refer to the same or parent query level are considered
- * parallel-safe. The idea is that we compute such params at Gather or
- * Gather Merge node and pass their value to workers.
- */
- for (proot = root; proot != NULL; proot = proot->parent_root)
- {
- foreach(l, proot->init_plans)
- {
- SubPlan *initsubplan = (SubPlan *) lfirst(l);
-
- context.safe_param_ids = list_concat(context.safe_param_ids,
- initsubplan->setParam);
- }
- }
return !max_parallel_hazard_walker(node, &context);
}
@@ -811,39 +790,34 @@ max_parallel_hazard_walker(Node *node, max_parallel_hazard_context *context)
}
/*
- * Only parallel-safe SubPlans can be sent to workers. Within the
- * testexpr of the SubPlan, Params representing the output columns of the
- * subplan can be treated as parallel-safe, so temporarily add their IDs
- * to the safe_param_ids list while examining the testexpr.
+ * Only parallel-safe SubPlans can be sent to workers.
*/
else if (IsA(node, SubPlan))
{
SubPlan *subplan = (SubPlan *) node;
- List *save_safe_param_ids;
if (!subplan->parallel_safe &&
max_parallel_hazard_test(PROPARALLEL_RESTRICTED, context))
return true;
- save_safe_param_ids = context->safe_param_ids;
- context->safe_param_ids = list_concat_copy(context->safe_param_ids,
- subplan->paramIds);
+
if (max_parallel_hazard_walker(subplan->testexpr, context))
- return true; /* no need to restore safe_param_ids */
- list_free(context->safe_param_ids);
- context->safe_param_ids = save_safe_param_ids;
- /* we must also check args, but no special Param treatment there */
+ return true;
+
if (max_parallel_hazard_walker((Node *) subplan->args, context))
return true;
+
/* don't want to recurse normally, so we're done */
return false;
}
/*
- * We can't pass Params to workers at the moment either, so they are also
- * parallel-restricted, unless they are PARAM_EXTERN Params or are
- * PARAM_EXEC Params listed in safe_param_ids, meaning they could be
- * either generated within workers or can be computed by the leader and
- * then their value can be passed to workers.
+ * We can't pass all types of Params to workers at the moment either.
+ * PARAM_EXTERN Params are always allowed. PARAM_EXEC Params are parallel-
+ * safe when they can be computed by the leader and their value passed to
+ * workers or are generated within a worker. However we don't always know
+ * whether a param will be generated within a worker when we are parsing a
+ * querytree. In that case we leave it to the consumer to verify that the
+ * current plan level provides these params.
*/
else if (IsA(node, Param))
{
@@ -852,12 +826,12 @@ max_parallel_hazard_walker(Node *node, max_parallel_hazard_context *context)
if (param->paramkind == PARAM_EXTERN)
return false;
- if (param->paramkind != PARAM_EXEC ||
- !list_member_int(context->safe_param_ids, param->paramid))
- {
- if (max_parallel_hazard_test(PROPARALLEL_RESTRICTED, context))
- return true;
- }
+ if (param->paramkind == PARAM_EXEC)
+ return false;
+
+ if (max_parallel_hazard_test(PROPARALLEL_RESTRICTED, context))
+ return true;
+
return false; /* nothing to recurse to */
}
diff --git a/src/test/regress/expected/incremental_sort.out b/src/test/regress/expected/incremental_sort.out
index 0c3433f8e5..2b52b0ca3c 100644
--- a/src/test/regress/expected/incremental_sort.out
+++ b/src/test/regress/expected/incremental_sort.out
@@ -1597,20 +1597,21 @@ explain (costs off) select distinct
unique1,
(select t.unique1 from tenk1 where tenk1.unique1 = t.unique1)
from tenk1 t, generate_series(1, 1000);
- QUERY PLAN
----------------------------------------------------------------------------------
+ QUERY PLAN
+---------------------------------------------------------------------------------------
Unique
- -> Sort
- Sort Key: t.unique1, ((SubPlan 1))
- -> Gather
- Workers Planned: 2
- -> Nested Loop
- -> Parallel Index Only Scan using tenk1_unique1 on tenk1 t
- -> Function Scan on generate_series
- SubPlan 1
- -> Index Only Scan using tenk1_unique1 on tenk1
- Index Cond: (unique1 = t.unique1)
-(11 rows)
+ -> Gather Merge
+ Workers Planned: 2
+ -> Unique
+ -> Sort
+ Sort Key: t.unique1, ((SubPlan 1))
+ -> Nested Loop
+ -> Parallel Index Only Scan using tenk1_unique1 on tenk1 t
+ -> Function Scan on generate_series
+ SubPlan 1
+ -> Index Only Scan using tenk1_unique1 on tenk1
+ Index Cond: (unique1 = t.unique1)
+(12 rows)
explain (costs off) select
unique1,
@@ -1619,16 +1620,16 @@ from tenk1 t, generate_series(1, 1000)
order by 1, 2;
QUERY PLAN
---------------------------------------------------------------------------
- Sort
- Sort Key: t.unique1, ((SubPlan 1))
- -> Gather
- Workers Planned: 2
+ Gather Merge
+ Workers Planned: 2
+ -> Sort
+ Sort Key: t.unique1, ((SubPlan 1))
-> Nested Loop
-> Parallel Index Only Scan using tenk1_unique1 on tenk1 t
-> Function Scan on generate_series
- SubPlan 1
- -> Index Only Scan using tenk1_unique1 on tenk1
- Index Cond: (unique1 = t.unique1)
+ SubPlan 1
+ -> Index Only Scan using tenk1_unique1 on tenk1
+ Index Cond: (unique1 = t.unique1)
(10 rows)
-- Parallel sort but with expression not available until the upper rel.
diff --git a/src/test/regress/expected/partition_prune.out b/src/test/regress/expected/partition_prune.out
index 2abf759385..4566260fc4 100644
--- a/src/test/regress/expected/partition_prune.out
+++ b/src/test/regress/expected/partition_prune.out
@@ -1489,60 +1489,64 @@ EXPLAIN (VERBOSE, COSTS OFF) SELECT * FROM part p(x) ORDER BY x;
--
-- pruning won't work for mc3p, because some keys are Params
explain (costs off) select * from mc2p t1, lateral (select count(*) from mc3p t2 where t2.a = t1.b and abs(t2.b) = 1 and t2.c = 1) s where t1.a = 1;
- QUERY PLAN
------------------------------------------------------------------------
- Nested Loop
- -> Append
- -> Seq Scan on mc2p1 t1_1
- Filter: (a = 1)
- -> Seq Scan on mc2p2 t1_2
- Filter: (a = 1)
- -> Seq Scan on mc2p_default t1_3
- Filter: (a = 1)
- -> Aggregate
- -> Append
- -> Seq Scan on mc3p0 t2_1
- Filter: ((a = t1.b) AND (c = 1) AND (abs(b) = 1))
- -> Seq Scan on mc3p1 t2_2
- Filter: ((a = t1.b) AND (c = 1) AND (abs(b) = 1))
- -> Seq Scan on mc3p2 t2_3
- Filter: ((a = t1.b) AND (c = 1) AND (abs(b) = 1))
- -> Seq Scan on mc3p3 t2_4
- Filter: ((a = t1.b) AND (c = 1) AND (abs(b) = 1))
- -> Seq Scan on mc3p4 t2_5
- Filter: ((a = t1.b) AND (c = 1) AND (abs(b) = 1))
- -> Seq Scan on mc3p5 t2_6
- Filter: ((a = t1.b) AND (c = 1) AND (abs(b) = 1))
- -> Seq Scan on mc3p6 t2_7
- Filter: ((a = t1.b) AND (c = 1) AND (abs(b) = 1))
- -> Seq Scan on mc3p7 t2_8
- Filter: ((a = t1.b) AND (c = 1) AND (abs(b) = 1))
- -> Seq Scan on mc3p_default t2_9
- Filter: ((a = t1.b) AND (c = 1) AND (abs(b) = 1))
-(28 rows)
+ QUERY PLAN
+-----------------------------------------------------------------------------
+ Gather
+ Workers Planned: 2
+ -> Nested Loop
+ -> Parallel Append
+ -> Parallel Seq Scan on mc2p1 t1_1
+ Filter: (a = 1)
+ -> Parallel Seq Scan on mc2p2 t1_2
+ Filter: (a = 1)
+ -> Parallel Seq Scan on mc2p_default t1_3
+ Filter: (a = 1)
+ -> Aggregate
+ -> Append
+ -> Seq Scan on mc3p0 t2_1
+ Filter: ((a = t1.b) AND (c = 1) AND (abs(b) = 1))
+ -> Seq Scan on mc3p1 t2_2
+ Filter: ((a = t1.b) AND (c = 1) AND (abs(b) = 1))
+ -> Seq Scan on mc3p2 t2_3
+ Filter: ((a = t1.b) AND (c = 1) AND (abs(b) = 1))
+ -> Seq Scan on mc3p3 t2_4
+ Filter: ((a = t1.b) AND (c = 1) AND (abs(b) = 1))
+ -> Seq Scan on mc3p4 t2_5
+ Filter: ((a = t1.b) AND (c = 1) AND (abs(b) = 1))
+ -> Seq Scan on mc3p5 t2_6
+ Filter: ((a = t1.b) AND (c = 1) AND (abs(b) = 1))
+ -> Seq Scan on mc3p6 t2_7
+ Filter: ((a = t1.b) AND (c = 1) AND (abs(b) = 1))
+ -> Seq Scan on mc3p7 t2_8
+ Filter: ((a = t1.b) AND (c = 1) AND (abs(b) = 1))
+ -> Seq Scan on mc3p_default t2_9
+ Filter: ((a = t1.b) AND (c = 1) AND (abs(b) = 1))
+(30 rows)
-- pruning should work fine, because values for a prefix of keys (a, b) are
-- available
explain (costs off) select * from mc2p t1, lateral (select count(*) from mc3p t2 where t2.c = t1.b and abs(t2.b) = 1 and t2.a = 1) s where t1.a = 1;
- QUERY PLAN
------------------------------------------------------------------------
- Nested Loop
- -> Append
- -> Seq Scan on mc2p1 t1_1
- Filter: (a = 1)
- -> Seq Scan on mc2p2 t1_2
- Filter: (a = 1)
- -> Seq Scan on mc2p_default t1_3
- Filter: (a = 1)
- -> Aggregate
- -> Append
- -> Seq Scan on mc3p0 t2_1
- Filter: ((c = t1.b) AND (a = 1) AND (abs(b) = 1))
- -> Seq Scan on mc3p1 t2_2
- Filter: ((c = t1.b) AND (a = 1) AND (abs(b) = 1))
- -> Seq Scan on mc3p_default t2_3
- Filter: ((c = t1.b) AND (a = 1) AND (abs(b) = 1))
-(16 rows)
+ QUERY PLAN
+-----------------------------------------------------------------------------
+ Gather
+ Workers Planned: 2
+ -> Nested Loop
+ -> Parallel Append
+ -> Parallel Seq Scan on mc2p1 t1_1
+ Filter: (a = 1)
+ -> Parallel Seq Scan on mc2p2 t1_2
+ Filter: (a = 1)
+ -> Parallel Seq Scan on mc2p_default t1_3
+ Filter: (a = 1)
+ -> Aggregate
+ -> Append
+ -> Seq Scan on mc3p0 t2_1
+ Filter: ((c = t1.b) AND (a = 1) AND (abs(b) = 1))
+ -> Seq Scan on mc3p1 t2_2
+ Filter: ((c = t1.b) AND (a = 1) AND (abs(b) = 1))
+ -> Seq Scan on mc3p_default t2_3
+ Filter: ((c = t1.b) AND (a = 1) AND (abs(b) = 1))
+(18 rows)
-- also here, because values for all keys are provided
explain (costs off) select * from mc2p t1, lateral (select count(*) from mc3p t2 where t2.a = 1 and abs(t2.b) = 1 and t2.c = 1) s where t1.a = 1;
diff --git a/src/test/regress/expected/select_parallel.out b/src/test/regress/expected/select_parallel.out
index 04810d2756..eb59b9437c 100644
--- a/src/test/regress/expected/select_parallel.out
+++ b/src/test/regress/expected/select_parallel.out
@@ -137,8 +137,8 @@ create table part_pa_test_p2 partition of part_pa_test for values from (0) to (m
explain (costs off)
select (select max((select pa1.b from part_pa_test pa1 where pa1.a = pa2.a)))
from part_pa_test pa2;
- QUERY PLAN
---------------------------------------------------------------
+ QUERY PLAN
+----------------------------------------------------------------
Aggregate
-> Gather
Workers Planned: 3
@@ -148,12 +148,14 @@ explain (costs off)
SubPlan 2
-> Result
SubPlan 1
- -> Append
- -> Seq Scan on part_pa_test_p1 pa1_1
- Filter: (a = pa2.a)
- -> Seq Scan on part_pa_test_p2 pa1_2
- Filter: (a = pa2.a)
-(14 rows)
+ -> Gather
+ Workers Planned: 3
+ -> Parallel Append
+ -> Parallel Seq Scan on part_pa_test_p1 pa1_1
+ Filter: (a = pa2.a)
+ -> Parallel Seq Scan on part_pa_test_p2 pa1_2
+ Filter: (a = pa2.a)
+(16 rows)
drop table part_pa_test;
-- test with leader participation disabled
@@ -320,19 +322,19 @@ explain (costs off, verbose) select
QUERY PLAN
----------------------------------------------------------------------------
Gather
- Output: (SubPlan 1)
+ Output: ((SubPlan 1))
Workers Planned: 4
-> Nested Loop
- Output: t.unique1
+ Output: (SubPlan 1)
-> Parallel Index Only Scan using tenk1_unique1 on public.tenk1 t
Output: t.unique1
-> Function Scan on pg_catalog.generate_series
Output: generate_series.generate_series
Function Call: generate_series(1, 10)
- SubPlan 1
- -> Index Only Scan using tenk1_unique1 on public.tenk1
- Output: t.unique1
- Index Cond: (tenk1.unique1 = t.unique1)
+ SubPlan 1
+ -> Index Only Scan using tenk1_unique1 on public.tenk1
+ Output: t.unique1
+ Index Cond: (tenk1.unique1 = t.unique1)
(14 rows)
explain (costs off, verbose) select
@@ -341,63 +343,69 @@ explain (costs off, verbose) select
QUERY PLAN
----------------------------------------------------------------------
Gather
- Output: (SubPlan 1)
+ Output: ((SubPlan 1))
Workers Planned: 4
-> Parallel Index Only Scan using tenk1_unique1 on public.tenk1 t
- Output: t.unique1
- SubPlan 1
- -> Index Only Scan using tenk1_unique1 on public.tenk1
- Output: t.unique1
- Index Cond: (tenk1.unique1 = t.unique1)
+ Output: (SubPlan 1)
+ SubPlan 1
+ -> Index Only Scan using tenk1_unique1 on public.tenk1
+ Output: t.unique1
+ Index Cond: (tenk1.unique1 = t.unique1)
(9 rows)
explain (costs off, verbose) select
(select t.unique1 from tenk1 where tenk1.unique1 = t.unique1)
from tenk1 t
limit 1;
- QUERY PLAN
--------------------------------------------------------------------
+ QUERY PLAN
+----------------------------------------------------------------------------
Limit
Output: ((SubPlan 1))
- -> Seq Scan on public.tenk1 t
- Output: (SubPlan 1)
- SubPlan 1
- -> Index Only Scan using tenk1_unique1 on public.tenk1
- Output: t.unique1
- Index Cond: (tenk1.unique1 = t.unique1)
-(8 rows)
+ -> Gather
+ Output: ((SubPlan 1))
+ Workers Planned: 4
+ -> Parallel Index Only Scan using tenk1_unique1 on public.tenk1 t
+ Output: (SubPlan 1)
+ SubPlan 1
+ -> Index Only Scan using tenk1_unique1 on public.tenk1
+ Output: t.unique1
+ Index Cond: (tenk1.unique1 = t.unique1)
+(11 rows)
explain (costs off, verbose) select t.unique1
from tenk1 t
where t.unique1 = (select t.unique1 from tenk1 where tenk1.unique1 = t.unique1);
- QUERY PLAN
--------------------------------------------------------------
- Seq Scan on public.tenk1 t
+ QUERY PLAN
+----------------------------------------------------------------------
+ Gather
Output: t.unique1
- Filter: (t.unique1 = (SubPlan 1))
- SubPlan 1
- -> Index Only Scan using tenk1_unique1 on public.tenk1
- Output: t.unique1
- Index Cond: (tenk1.unique1 = t.unique1)
-(7 rows)
+ Workers Planned: 4
+ -> Parallel Index Only Scan using tenk1_unique1 on public.tenk1 t
+ Output: t.unique1
+ Filter: (t.unique1 = (SubPlan 1))
+ SubPlan 1
+ -> Index Only Scan using tenk1_unique1 on public.tenk1
+ Output: t.unique1
+ Index Cond: (tenk1.unique1 = t.unique1)
+(10 rows)
explain (costs off, verbose) select *
from tenk1 t
order by (select t.unique1 from tenk1 where tenk1.unique1 = t.unique1);
- QUERY PLAN
-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
- Sort
+ QUERY PLAN
+----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
+ Gather Merge
Output: t.unique1, t.unique2, t.two, t.four, t.ten, t.twenty, t.hundred, t.thousand, t.twothousand, t.fivethous, t.tenthous, t.odd, t.even, t.stringu1, t.stringu2, t.string4, ((SubPlan 1))
- Sort Key: ((SubPlan 1))
- -> Gather
- Output: t.unique1, t.unique2, t.two, t.four, t.ten, t.twenty, t.hundred, t.thousand, t.twothousand, t.fivethous, t.tenthous, t.odd, t.even, t.stringu1, t.stringu2, t.string4, (SubPlan 1)
- Workers Planned: 4
+ Workers Planned: 4
+ -> Sort
+ Output: t.unique1, t.unique2, t.two, t.four, t.ten, t.twenty, t.hundred, t.thousand, t.twothousand, t.fivethous, t.tenthous, t.odd, t.even, t.stringu1, t.stringu2, t.string4, ((SubPlan 1))
+ Sort Key: ((SubPlan 1))
-> Parallel Seq Scan on public.tenk1 t
- Output: t.unique1, t.unique2, t.two, t.four, t.ten, t.twenty, t.hundred, t.thousand, t.twothousand, t.fivethous, t.tenthous, t.odd, t.even, t.stringu1, t.stringu2, t.string4
- SubPlan 1
- -> Index Only Scan using tenk1_unique1 on public.tenk1
- Output: t.unique1
- Index Cond: (tenk1.unique1 = t.unique1)
+ Output: t.unique1, t.unique2, t.two, t.four, t.ten, t.twenty, t.hundred, t.thousand, t.twothousand, t.fivethous, t.tenthous, t.odd, t.even, t.stringu1, t.stringu2, t.string4, (SubPlan 1)
+ SubPlan 1
+ -> Index Only Scan using tenk1_unique1 on public.tenk1
+ Output: t.unique1
+ Index Cond: (tenk1.unique1 = t.unique1)
(12 rows)
-- test subplan in join/lateral join
@@ -409,14 +417,14 @@ explain (costs off, verbose, timing off) select t.unique1, l.*
QUERY PLAN
----------------------------------------------------------------------
Gather
- Output: t.unique1, (SubPlan 1)
+ Output: t.unique1, ((SubPlan 1))
Workers Planned: 4
-> Parallel Index Only Scan using tenk1_unique1 on public.tenk1 t
- Output: t.unique1
- SubPlan 1
- -> Index Only Scan using tenk1_unique1 on public.tenk1
- Output: t.unique1
- Index Cond: (tenk1.unique1 = t.unique1)
+ Output: t.unique1, (SubPlan 1)
+ SubPlan 1
+ -> Index Only Scan using tenk1_unique1 on public.tenk1
+ Output: t.unique1
+ Index Cond: (tenk1.unique1 = t.unique1)
(9 rows)
-- this is not parallel-safe due to use of random() within SubLink's testexpr:
@@ -1322,8 +1330,10 @@ SELECT 1 FROM tenk1_vw_sec
-> Parallel Index Only Scan using tenk1_unique1 on tenk1
SubPlan 1
-> Aggregate
- -> Seq Scan on int4_tbl
- Filter: (f1 < tenk1_vw_sec.unique1)
-(9 rows)
+ -> Gather
+ Workers Planned: 1
+ -> Parallel Seq Scan on int4_tbl
+ Filter: (f1 < tenk1_vw_sec.unique1)
+(11 rows)
rollback;
--
2.39.2 (Apple Git-143)
^ permalink raw reply [nested|flat] 35+ messages in thread
* Re: Parallelize correlated subqueries that execute within each worker
@ 2023-06-26 06:47 Richard Guo <[email protected]>
parent: James Coleman <[email protected]>
1 sibling, 0 replies; 35+ messages in thread
From: Richard Guo @ 2023-06-26 06:47 UTC (permalink / raw)
To: James Coleman <[email protected]>; +Cc: Tomas Vondra <[email protected]>; vignesh C <[email protected]>; Andres Freund <[email protected]>; Robert Haas <[email protected]>; pgsql-hackers; Amit Kapila <[email protected]>; Tom Lane <[email protected]>
On Mon, Jun 12, 2023 at 10:23 AM James Coleman <[email protected]> wrote:
> BTW are you by any chance testing on ARM macOS? I reproduced the issue
> there, but for some reason I did not reproduce the error (and the plan
> wasn't parallelized) when I tested this on linux. Perhaps I missed
> setting something up; it seems odd.
Hmm, that's weird. I was also testing that query on linux. But please
note that several GUC settings are needed to generate parallel plan for
that query.
set min_parallel_table_scan_size to 0;
set parallel_setup_cost to 0;
set parallel_tuple_cost to 0;
Thanks
Richard
^ permalink raw reply [nested|flat] 35+ messages in thread
* Re: Parallelize correlated subqueries that execute within each worker
@ 2023-07-04 01:26 James Coleman <[email protected]>
parent: James Coleman <[email protected]>
1 sibling, 1 reply; 35+ messages in thread
From: James Coleman @ 2023-07-04 01:26 UTC (permalink / raw)
To: Richard Guo <[email protected]>; +Cc: Tomas Vondra <[email protected]>; vignesh C <[email protected]>; Andres Freund <[email protected]>; Robert Haas <[email protected]>; pgsql-hackers; Amit Kapila <[email protected]>; Tom Lane <[email protected]>
On Sun, Jun 11, 2023 at 10:23 PM James Coleman <[email protected]> wrote:
>
> ...
> > And while trying the v9 patch I came across a crash with the query
> > below.
> >
> > set min_parallel_table_scan_size to 0;
> > set parallel_setup_cost to 0;
> > set parallel_tuple_cost to 0;
> >
> > explain (costs off)
> > select * from pg_description t1 where objoid in
> > (select objoid from pg_description t2 where t2.description = t1.description);
> > QUERY PLAN
> > --------------------------------------------------------
> > Seq Scan on pg_description t1
> > Filter: (SubPlan 1)
> > SubPlan 1
> > -> Gather
> > Workers Planned: 2
> > -> Parallel Seq Scan on pg_description t2
> > Filter: (description = t1.description)
> > (7 rows)
> >
> > select * from pg_description t1 where objoid in
> > (select objoid from pg_description t2 where t2.description = t1.description);
> > WARNING: terminating connection because of crash of another server process
> >
> > Seems something is wrong when extracting the argument from the Param in
> > parallel worker.
>
> With what I'm trying to change I don't think this plan should ever be
> generated since it means we'd have to pass a param from the outer seq
> scan into the parallel subplan, which we can't do (currently).
>
> I've attached the full backtrace to the email, but as you hinted at
> the parallel worker is trying to get the param (in this case
> detoasting it), but the param doesn't exist on the worker, so it seg
> faults. Looking at this further I think there's an existing test case
> that exposes the misplanning here (the one right under the comment
> "Parallel Append is not to be used when the subpath depends on the
> outer param" in select_parallel.sql), but it doesn't seg fault because
> the param is an integer, doesn't need to be detoasted, and therefore
> (I think) we skate by (but probably with wrong results in depending on
> the dataset).
>
> Interestingly this is one of the existing test queries my original
> patch approach didn't change, so this gives me something specific to
> work with improving the path. Thanks for testing this and bringing
> this to my attention!
Here's what I've found debugging this:
There's only a single gather path ever created when planning this
query, making it easy to know which one is the problem. That gather
path is created with this stacktrace:
frame #0: 0x0000000105291590
postgres`create_gather_path(root=0x000000013081ae78,
rel=0x000000013080c8e8, subpath=0x000000013081c080,
target=0x000000013081c8c0, required_outer=0x0000000000000000,
rows=0x0000000000000000) at pathnode.c:1971:2
frame #1: 0x0000000105208e54
postgres`generate_gather_paths(root=0x000000013081ae78,
rel=0x000000013080c8e8, override_rows=false) at allpaths.c:3097:4
frame #2: 0x00000001052090ec
postgres`generate_useful_gather_paths(root=0x000000013081ae78,
rel=0x000000013080c8e8, override_rows=false) at allpaths.c:3241:2
frame #3: 0x0000000105258754
postgres`apply_scanjoin_target_to_paths(root=0x000000013081ae78,
rel=0x000000013080c8e8, scanjoin_targets=0x000000013081c978,
scanjoin_targets_contain_srfs=0x0000000000000000,
scanjoin_target_parallel_safe=true, tlist_same_exprs=true) at
planner.c:7696:3
frame #4: 0x00000001052533cc
postgres`grouping_planner(root=0x000000013081ae78, tuple_fraction=0.5)
at planner.c:1611:3
frame #5: 0x0000000105251e9c
postgres`subquery_planner(glob=0x00000001308188d8,
parse=0x000000013080caf8, parent_root=0x000000013080cc38,
hasRecursion=false, tuple_fraction=0.5) at planner.c:1062:2
frame #6: 0x000000010526b134
postgres`make_subplan(root=0x000000013080cc38,
orig_subquery=0x000000013080ff58, subLinkType=ANY_SUBLINK,
subLinkId=0, testexpr=0x000000013080d848, isTopQual=true) at
subselect.c:221:12
frame #7: 0x0000000105268b8c
postgres`process_sublinks_mutator(node=0x000000013080d6d8,
context=0x000000016b0998f8) at subselect.c:1950:10
frame #8: 0x0000000105268ad8
postgres`SS_process_sublinks(root=0x000000013080cc38,
expr=0x000000013080d6d8, isQual=true) at subselect.c:1923:9
frame #9: 0x00000001052527b8
postgres`preprocess_expression(root=0x000000013080cc38,
expr=0x000000013080d6d8, kind=0) at planner.c:1169:10
frame #10: 0x0000000105252954
postgres`preprocess_qual_conditions(root=0x000000013080cc38,
jtnode=0x000000013080d108) at planner.c:1214:14
frame #11: 0x0000000105251580
postgres`subquery_planner(glob=0x00000001308188d8,
parse=0x0000000137010d68, parent_root=0x0000000000000000,
hasRecursion=false, tuple_fraction=0) at planner.c:832:2
frame #12: 0x000000010525042c
postgres`standard_planner(parse=0x0000000137010d68,
query_string="explain (costs off)\nselect * from pg_description t1
where objoid in\n (select objoid from pg_description t2 where
t2.description = t1.description);", cursorOptions=2048,
boundParams=0x0000000000000000) at planner.c:411:9
There aren't any lateral markings on the rels. Additionally the
partial path has param_info=null (I found out from Tom in a separate
thread [1] that this is only set for outer relations from the same
query level).
The only param that I could easily find at first was a single param of
type PARAM_EXTERN in root->plan_params in make_subplan().
I spent a lot of time trying to figure out where we could find the
PARAM_EXEC param that's being fed into the subplan, but it doesn't
seem like we have access to any of these things at the point in the
path creation process that it's interesting to us when inserting the
gather nodes.
Given all of that I settled on this approach:
1. Modify is_parallel_safe() to by default ignore PARAM_EXEC params.
2. Add is_parallel_safe_with_params() that checks for the existence of
such params.
3. Store the required params in a bitmapset on each base rel.
4. Union the bitmapset on join rels.
5. Only insert a gather node if that bitmapset is empty.
I have an intuition that there's some spot (e.g. joins) that we should
be removing params from this set (e.g., when we've satisfied them),
but I haven't been able to come up with such a scenario as yet.
The attached v11 fixes the issue you reported.
Thanks,
James Coleman
Attachments:
[application/octet-stream] v11-0002-Parallelize-correlated-subqueries.patch (27.5K, ../../CAAaqYe8F=TNEF7Dk98dgLkksBt9T0QweTZ4kfif9+q5MKtxQ0Q@mail.gmail.com/2-v11-0002-Parallelize-correlated-subqueries.patch)
download | inline diff:
From 7c19d7f498375cd3ee6b676226c1a9b627298c5f Mon Sep 17 00:00:00 2001
From: jcoleman <[email protected]>
Date: Sun, 2 Jul 2023 15:23:49 -0400
Subject: [PATCH v11 2/2] Parallelize correlated subqueries
When params are provided at the current query level (i.e., are generated
within a single worker and not shared across workers) we can safely
execute these in parallel.
We accomplish this by tracking the PARAM_EXEC params that are needed for
a rel to be safely executed in parallel and only inserting a Gather node
if that set is empty.
---
doc/src/sgml/parallel.sgml | 3 +-
src/backend/optimizer/path/allpaths.c | 24 +++-
src/backend/optimizer/util/clauses.c | 73 +++++++++--
src/backend/optimizer/util/relnode.c | 1 +
src/include/nodes/pathnodes.h | 6 +
src/include/optimizer/clauses.h | 1 +
.../regress/expected/incremental_sort.out | 41 +++----
src/test/regress/expected/partition_prune.out | 104 ++++++++--------
src/test/regress/expected/select_parallel.out | 113 ++++++++++--------
9 files changed, 227 insertions(+), 139 deletions(-)
diff --git a/doc/src/sgml/parallel.sgml b/doc/src/sgml/parallel.sgml
index 5acc9537d6..fd32572ec8 100644
--- a/doc/src/sgml/parallel.sgml
+++ b/doc/src/sgml/parallel.sgml
@@ -518,7 +518,8 @@ EXPLAIN SELECT * FROM pgbench_accounts WHERE filler LIKE '%x%';
<listitem>
<para>
- Plan nodes that reference a correlated <literal>SubPlan</literal>.
+ Plan nodes that reference a correlated <literal>SubPlan</literal> where
+ the result is shared between workers.
</para>
</listitem>
</itemizedlist>
diff --git a/src/backend/optimizer/path/allpaths.c b/src/backend/optimizer/path/allpaths.c
index 9bdc70c702..cebad18319 100644
--- a/src/backend/optimizer/path/allpaths.c
+++ b/src/backend/optimizer/path/allpaths.c
@@ -632,7 +632,7 @@ set_rel_consider_parallel(PlannerInfo *root, RelOptInfo *rel,
if (proparallel != PROPARALLEL_SAFE)
return;
- if (!is_parallel_safe(root, (Node *) rte->tablesample->args))
+ if (!is_parallel_safe_with_params(root, (Node *) rte->tablesample->args, &rel->params_req_for_parallel))
return;
}
@@ -698,7 +698,7 @@ set_rel_consider_parallel(PlannerInfo *root, RelOptInfo *rel,
case RTE_FUNCTION:
/* Check for parallel-restricted functions. */
- if (!is_parallel_safe(root, (Node *) rte->functions))
+ if (!is_parallel_safe_with_params(root, (Node *) rte->functions, &rel->params_req_for_parallel))
return;
break;
@@ -708,7 +708,7 @@ set_rel_consider_parallel(PlannerInfo *root, RelOptInfo *rel,
case RTE_VALUES:
/* Check for parallel-restricted functions. */
- if (!is_parallel_safe(root, (Node *) rte->values_lists))
+ if (!is_parallel_safe_with_params(root, (Node *) rte->values_lists, &rel->params_req_for_parallel))
return;
break;
@@ -745,14 +745,14 @@ set_rel_consider_parallel(PlannerInfo *root, RelOptInfo *rel,
* outer join clauses work correctly. It would likely break equivalence
* classes, too.
*/
- if (!is_parallel_safe(root, (Node *) rel->baserestrictinfo))
+ if (!is_parallel_safe_with_params(root, (Node *) rel->baserestrictinfo, &rel->params_req_for_parallel))
return;
/*
* Likewise, if the relation's outputs are not parallel-safe, give up.
* (Usually, they're just Vars, but sometimes they're not.)
*/
- if (!is_parallel_safe(root, (Node *) rel->reltarget->exprs))
+ if (!is_parallel_safe_with_params(root, (Node *) rel->reltarget->exprs, &rel->params_req_for_parallel))
return;
/* We have a winner. */
@@ -3069,6 +3069,13 @@ generate_gather_paths(PlannerInfo *root, RelOptInfo *rel, bool override_rows)
if (rel->partial_pathlist == NIL)
return;
+ /*
+ * Wait to insert Gather nodes until all PARAM_EXEC params are provided
+ * within the current rel since we can't pass them to workers.
+ */
+ if (!bms_is_empty(rel->params_req_for_parallel))
+ return;
+
/* Should we override the rel's rowcount estimate? */
if (override_rows)
rowsp = &rows;
@@ -3207,6 +3214,13 @@ generate_useful_gather_paths(PlannerInfo *root, RelOptInfo *rel, bool override_r
if (rel->partial_pathlist == NIL)
return;
+ /*
+ * Wait to insert Gather nodes until all PARAM_EXEC params are provided
+ * within the current rel since we can't pass them to workers.
+ */
+ if (!bms_is_empty(rel->params_req_for_parallel))
+ return;
+
/* Should we override the rel's rowcount estimate? */
if (override_rows)
rowsp = &rows;
diff --git a/src/backend/optimizer/util/clauses.c b/src/backend/optimizer/util/clauses.c
index 7f453b04f8..a82a7835c4 100644
--- a/src/backend/optimizer/util/clauses.c
+++ b/src/backend/optimizer/util/clauses.c
@@ -91,6 +91,8 @@ typedef struct
{
char max_hazard; /* worst proparallel hazard found so far */
char max_interesting; /* worst proparallel hazard of interest */
+ bool check_params;
+ Bitmapset **required_params;
List *safe_param_ids; /* PARAM_EXEC Param IDs to treat as safe */
} max_parallel_hazard_context;
@@ -654,6 +656,7 @@ max_parallel_hazard(Query *parse)
context.max_hazard = PROPARALLEL_SAFE;
context.max_interesting = PROPARALLEL_UNSAFE;
+ context.check_params = true;
context.safe_param_ids = NIL;
(void) max_parallel_hazard_walker((Node *) parse, &context);
return context.max_hazard;
@@ -670,8 +673,6 @@ bool
is_parallel_safe(PlannerInfo *root, Node *node)
{
max_parallel_hazard_context context;
- PlannerInfo *proot;
- ListCell *l;
/*
* Even if the original querytree contained nothing unsafe, we need to
@@ -685,6 +686,43 @@ is_parallel_safe(PlannerInfo *root, Node *node)
/* Else use max_parallel_hazard's search logic, but stop on RESTRICTED */
context.max_hazard = PROPARALLEL_SAFE;
context.max_interesting = PROPARALLEL_RESTRICTED;
+ context.check_params = false;
+ context.required_params = NULL;
+
+ return !max_parallel_hazard_walker(node, &context);
+}
+
+/*
+ * is_parallel_safe_with_params
+ * As above, but additionally tracking what PARAM_EXEC params required to
+ * be provided within a worker for a gather to be inserted at this level
+ * of the query. Those required params are passed to the caller through
+ * the required_params argument.
+ *
+ * Note: required_params is only valid if node is otherwise parallel safe.
+ */
+bool
+is_parallel_safe_with_params(PlannerInfo *root, Node *node, Bitmapset **required_params)
+{
+ max_parallel_hazard_context context;
+ PlannerInfo *proot;
+ ListCell *l;
+
+ /*
+ * Even if the original querytree contained nothing unsafe, we need to
+ * search the expression if we have generated any PARAM_EXEC Params while
+ * planning, because those will have to be provided for the expression to
+ * remain parallel safe and there might be one in this expression. But
+ * otherwise we don't need to look.
+ */
+ if (root->glob->maxParallelHazard == PROPARALLEL_SAFE &&
+ root->glob->paramExecTypes == NIL)
+ return true;
+ /* Else use max_parallel_hazard's search logic, but stop on RESTRICTED */
+ context.max_hazard = PROPARALLEL_SAFE;
+ context.max_interesting = PROPARALLEL_RESTRICTED;
+ context.check_params = false;
+ context.required_params = required_params;
context.safe_param_ids = NIL;
/*
@@ -824,13 +862,22 @@ max_parallel_hazard_walker(Node *node, max_parallel_hazard_context *context)
if (!subplan->parallel_safe &&
max_parallel_hazard_test(PROPARALLEL_RESTRICTED, context))
return true;
- save_safe_param_ids = context->safe_param_ids;
- context->safe_param_ids = list_concat_copy(context->safe_param_ids,
- subplan->paramIds);
+
+ if (context->check_params || context->required_params != NULL)
+ {
+ save_safe_param_ids = context->safe_param_ids;
+ context->safe_param_ids = list_concat_copy(context->safe_param_ids,
+ subplan->paramIds);
+ }
if (max_parallel_hazard_walker(subplan->testexpr, context))
return true; /* no need to restore safe_param_ids */
- list_free(context->safe_param_ids);
- context->safe_param_ids = save_safe_param_ids;
+
+ if (context->check_params || context->required_params != NULL)
+ {
+ list_free(context->safe_param_ids);
+ context->safe_param_ids = save_safe_param_ids;
+ }
+
/* we must also check args, but no special Param treatment there */
if (max_parallel_hazard_walker((Node *) subplan->args, context))
return true;
@@ -849,14 +896,18 @@ max_parallel_hazard_walker(Node *node, max_parallel_hazard_context *context)
{
Param *param = (Param *) node;
- if (param->paramkind == PARAM_EXTERN)
+ if (param->paramkind != PARAM_EXEC || !(context->check_params || context->required_params != NULL))
return false;
- if (param->paramkind != PARAM_EXEC ||
- !list_member_int(context->safe_param_ids, param->paramid))
+ if (!list_member_int(context->safe_param_ids, param->paramid))
{
if (max_parallel_hazard_test(PROPARALLEL_RESTRICTED, context))
- return true;
+ {
+ if (context->required_params != NULL)
+ *context->required_params = bms_add_member(*context->required_params, param->paramid);
+ if (context->check_params)
+ return true;
+ }
}
return false; /* nothing to recurse to */
}
diff --git a/src/backend/optimizer/util/relnode.c b/src/backend/optimizer/util/relnode.c
index 15e3910b79..2e12a61ceb 100644
--- a/src/backend/optimizer/util/relnode.c
+++ b/src/backend/optimizer/util/relnode.c
@@ -687,6 +687,7 @@ build_join_rel(PlannerInfo *root,
joinrel->consider_startup = (root->tuple_fraction > 0);
joinrel->consider_param_startup = false;
joinrel->consider_parallel = false;
+ joinrel->params_req_for_parallel = bms_union(outer_rel->params_req_for_parallel, inner_rel->params_req_for_parallel);
joinrel->reltarget = create_empty_pathtarget();
joinrel->pathlist = NIL;
joinrel->ppilist = NIL;
diff --git a/src/include/nodes/pathnodes.h b/src/include/nodes/pathnodes.h
index c17b53f7ad..4966010fd0 100644
--- a/src/include/nodes/pathnodes.h
+++ b/src/include/nodes/pathnodes.h
@@ -871,6 +871,12 @@ typedef struct RelOptInfo
/* consider parallel paths? */
bool consider_parallel;
+ /*
+ * Params, if any, required to be provided when consider_parallel is true.
+ * Note: if consider_parallel is false then this is not meaningful.
+ */
+ Bitmapset *params_req_for_parallel;
+
/*
* default result targetlist for Paths scanning this relation; list of
* Vars/Exprs, cost, width
diff --git a/src/include/optimizer/clauses.h b/src/include/optimizer/clauses.h
index cbe0607e85..31cf484d0f 100644
--- a/src/include/optimizer/clauses.h
+++ b/src/include/optimizer/clauses.h
@@ -34,6 +34,7 @@ extern bool contain_subplans(Node *clause);
extern char max_parallel_hazard(Query *parse);
extern bool is_parallel_safe(PlannerInfo *root, Node *node);
+extern bool is_parallel_safe_with_params(PlannerInfo *root, Node *node, Bitmapset **required_params);
extern bool contain_nonstrict_functions(Node *clause);
extern bool contain_exec_param(Node *clause, List *param_ids);
extern bool contain_leaked_vars(Node *clause);
diff --git a/src/test/regress/expected/incremental_sort.out b/src/test/regress/expected/incremental_sort.out
index 0c3433f8e5..2b52b0ca3c 100644
--- a/src/test/regress/expected/incremental_sort.out
+++ b/src/test/regress/expected/incremental_sort.out
@@ -1597,20 +1597,21 @@ explain (costs off) select distinct
unique1,
(select t.unique1 from tenk1 where tenk1.unique1 = t.unique1)
from tenk1 t, generate_series(1, 1000);
- QUERY PLAN
----------------------------------------------------------------------------------
+ QUERY PLAN
+---------------------------------------------------------------------------------------
Unique
- -> Sort
- Sort Key: t.unique1, ((SubPlan 1))
- -> Gather
- Workers Planned: 2
- -> Nested Loop
- -> Parallel Index Only Scan using tenk1_unique1 on tenk1 t
- -> Function Scan on generate_series
- SubPlan 1
- -> Index Only Scan using tenk1_unique1 on tenk1
- Index Cond: (unique1 = t.unique1)
-(11 rows)
+ -> Gather Merge
+ Workers Planned: 2
+ -> Unique
+ -> Sort
+ Sort Key: t.unique1, ((SubPlan 1))
+ -> Nested Loop
+ -> Parallel Index Only Scan using tenk1_unique1 on tenk1 t
+ -> Function Scan on generate_series
+ SubPlan 1
+ -> Index Only Scan using tenk1_unique1 on tenk1
+ Index Cond: (unique1 = t.unique1)
+(12 rows)
explain (costs off) select
unique1,
@@ -1619,16 +1620,16 @@ from tenk1 t, generate_series(1, 1000)
order by 1, 2;
QUERY PLAN
---------------------------------------------------------------------------
- Sort
- Sort Key: t.unique1, ((SubPlan 1))
- -> Gather
- Workers Planned: 2
+ Gather Merge
+ Workers Planned: 2
+ -> Sort
+ Sort Key: t.unique1, ((SubPlan 1))
-> Nested Loop
-> Parallel Index Only Scan using tenk1_unique1 on tenk1 t
-> Function Scan on generate_series
- SubPlan 1
- -> Index Only Scan using tenk1_unique1 on tenk1
- Index Cond: (unique1 = t.unique1)
+ SubPlan 1
+ -> Index Only Scan using tenk1_unique1 on tenk1
+ Index Cond: (unique1 = t.unique1)
(10 rows)
-- Parallel sort but with expression not available until the upper rel.
diff --git a/src/test/regress/expected/partition_prune.out b/src/test/regress/expected/partition_prune.out
index 2abf759385..4566260fc4 100644
--- a/src/test/regress/expected/partition_prune.out
+++ b/src/test/regress/expected/partition_prune.out
@@ -1489,60 +1489,64 @@ EXPLAIN (VERBOSE, COSTS OFF) SELECT * FROM part p(x) ORDER BY x;
--
-- pruning won't work for mc3p, because some keys are Params
explain (costs off) select * from mc2p t1, lateral (select count(*) from mc3p t2 where t2.a = t1.b and abs(t2.b) = 1 and t2.c = 1) s where t1.a = 1;
- QUERY PLAN
------------------------------------------------------------------------
- Nested Loop
- -> Append
- -> Seq Scan on mc2p1 t1_1
- Filter: (a = 1)
- -> Seq Scan on mc2p2 t1_2
- Filter: (a = 1)
- -> Seq Scan on mc2p_default t1_3
- Filter: (a = 1)
- -> Aggregate
- -> Append
- -> Seq Scan on mc3p0 t2_1
- Filter: ((a = t1.b) AND (c = 1) AND (abs(b) = 1))
- -> Seq Scan on mc3p1 t2_2
- Filter: ((a = t1.b) AND (c = 1) AND (abs(b) = 1))
- -> Seq Scan on mc3p2 t2_3
- Filter: ((a = t1.b) AND (c = 1) AND (abs(b) = 1))
- -> Seq Scan on mc3p3 t2_4
- Filter: ((a = t1.b) AND (c = 1) AND (abs(b) = 1))
- -> Seq Scan on mc3p4 t2_5
- Filter: ((a = t1.b) AND (c = 1) AND (abs(b) = 1))
- -> Seq Scan on mc3p5 t2_6
- Filter: ((a = t1.b) AND (c = 1) AND (abs(b) = 1))
- -> Seq Scan on mc3p6 t2_7
- Filter: ((a = t1.b) AND (c = 1) AND (abs(b) = 1))
- -> Seq Scan on mc3p7 t2_8
- Filter: ((a = t1.b) AND (c = 1) AND (abs(b) = 1))
- -> Seq Scan on mc3p_default t2_9
- Filter: ((a = t1.b) AND (c = 1) AND (abs(b) = 1))
-(28 rows)
+ QUERY PLAN
+-----------------------------------------------------------------------------
+ Gather
+ Workers Planned: 2
+ -> Nested Loop
+ -> Parallel Append
+ -> Parallel Seq Scan on mc2p1 t1_1
+ Filter: (a = 1)
+ -> Parallel Seq Scan on mc2p2 t1_2
+ Filter: (a = 1)
+ -> Parallel Seq Scan on mc2p_default t1_3
+ Filter: (a = 1)
+ -> Aggregate
+ -> Append
+ -> Seq Scan on mc3p0 t2_1
+ Filter: ((a = t1.b) AND (c = 1) AND (abs(b) = 1))
+ -> Seq Scan on mc3p1 t2_2
+ Filter: ((a = t1.b) AND (c = 1) AND (abs(b) = 1))
+ -> Seq Scan on mc3p2 t2_3
+ Filter: ((a = t1.b) AND (c = 1) AND (abs(b) = 1))
+ -> Seq Scan on mc3p3 t2_4
+ Filter: ((a = t1.b) AND (c = 1) AND (abs(b) = 1))
+ -> Seq Scan on mc3p4 t2_5
+ Filter: ((a = t1.b) AND (c = 1) AND (abs(b) = 1))
+ -> Seq Scan on mc3p5 t2_6
+ Filter: ((a = t1.b) AND (c = 1) AND (abs(b) = 1))
+ -> Seq Scan on mc3p6 t2_7
+ Filter: ((a = t1.b) AND (c = 1) AND (abs(b) = 1))
+ -> Seq Scan on mc3p7 t2_8
+ Filter: ((a = t1.b) AND (c = 1) AND (abs(b) = 1))
+ -> Seq Scan on mc3p_default t2_9
+ Filter: ((a = t1.b) AND (c = 1) AND (abs(b) = 1))
+(30 rows)
-- pruning should work fine, because values for a prefix of keys (a, b) are
-- available
explain (costs off) select * from mc2p t1, lateral (select count(*) from mc3p t2 where t2.c = t1.b and abs(t2.b) = 1 and t2.a = 1) s where t1.a = 1;
- QUERY PLAN
------------------------------------------------------------------------
- Nested Loop
- -> Append
- -> Seq Scan on mc2p1 t1_1
- Filter: (a = 1)
- -> Seq Scan on mc2p2 t1_2
- Filter: (a = 1)
- -> Seq Scan on mc2p_default t1_3
- Filter: (a = 1)
- -> Aggregate
- -> Append
- -> Seq Scan on mc3p0 t2_1
- Filter: ((c = t1.b) AND (a = 1) AND (abs(b) = 1))
- -> Seq Scan on mc3p1 t2_2
- Filter: ((c = t1.b) AND (a = 1) AND (abs(b) = 1))
- -> Seq Scan on mc3p_default t2_3
- Filter: ((c = t1.b) AND (a = 1) AND (abs(b) = 1))
-(16 rows)
+ QUERY PLAN
+-----------------------------------------------------------------------------
+ Gather
+ Workers Planned: 2
+ -> Nested Loop
+ -> Parallel Append
+ -> Parallel Seq Scan on mc2p1 t1_1
+ Filter: (a = 1)
+ -> Parallel Seq Scan on mc2p2 t1_2
+ Filter: (a = 1)
+ -> Parallel Seq Scan on mc2p_default t1_3
+ Filter: (a = 1)
+ -> Aggregate
+ -> Append
+ -> Seq Scan on mc3p0 t2_1
+ Filter: ((c = t1.b) AND (a = 1) AND (abs(b) = 1))
+ -> Seq Scan on mc3p1 t2_2
+ Filter: ((c = t1.b) AND (a = 1) AND (abs(b) = 1))
+ -> Seq Scan on mc3p_default t2_3
+ Filter: ((c = t1.b) AND (a = 1) AND (abs(b) = 1))
+(18 rows)
-- also here, because values for all keys are provided
explain (costs off) select * from mc2p t1, lateral (select count(*) from mc3p t2 where t2.a = 1 and abs(t2.b) = 1 and t2.c = 1) s where t1.a = 1;
diff --git a/src/test/regress/expected/select_parallel.out b/src/test/regress/expected/select_parallel.out
index 0ddcf8e0b1..e422854574 100644
--- a/src/test/regress/expected/select_parallel.out
+++ b/src/test/regress/expected/select_parallel.out
@@ -320,19 +320,19 @@ explain (costs off, verbose) select
QUERY PLAN
----------------------------------------------------------------------------
Gather
- Output: (SubPlan 1)
+ Output: ((SubPlan 1))
Workers Planned: 4
-> Nested Loop
- Output: t.unique1
+ Output: (SubPlan 1)
-> Parallel Index Only Scan using tenk1_unique1 on public.tenk1 t
Output: t.unique1
-> Function Scan on pg_catalog.generate_series
Output: generate_series.generate_series
Function Call: generate_series(1, 10)
- SubPlan 1
- -> Index Only Scan using tenk1_unique1 on public.tenk1
- Output: t.unique1
- Index Cond: (tenk1.unique1 = t.unique1)
+ SubPlan 1
+ -> Index Only Scan using tenk1_unique1 on public.tenk1
+ Output: t.unique1
+ Index Cond: (tenk1.unique1 = t.unique1)
(14 rows)
explain (costs off, verbose) select
@@ -341,63 +341,69 @@ explain (costs off, verbose) select
QUERY PLAN
----------------------------------------------------------------------
Gather
- Output: (SubPlan 1)
+ Output: ((SubPlan 1))
Workers Planned: 4
-> Parallel Index Only Scan using tenk1_unique1 on public.tenk1 t
- Output: t.unique1
- SubPlan 1
- -> Index Only Scan using tenk1_unique1 on public.tenk1
- Output: t.unique1
- Index Cond: (tenk1.unique1 = t.unique1)
+ Output: (SubPlan 1)
+ SubPlan 1
+ -> Index Only Scan using tenk1_unique1 on public.tenk1
+ Output: t.unique1
+ Index Cond: (tenk1.unique1 = t.unique1)
(9 rows)
explain (costs off, verbose) select
(select t.unique1 from tenk1 where tenk1.unique1 = t.unique1)
from tenk1 t
limit 1;
- QUERY PLAN
--------------------------------------------------------------------
+ QUERY PLAN
+----------------------------------------------------------------------------
Limit
Output: ((SubPlan 1))
- -> Seq Scan on public.tenk1 t
- Output: (SubPlan 1)
- SubPlan 1
- -> Index Only Scan using tenk1_unique1 on public.tenk1
- Output: t.unique1
- Index Cond: (tenk1.unique1 = t.unique1)
-(8 rows)
+ -> Gather
+ Output: ((SubPlan 1))
+ Workers Planned: 4
+ -> Parallel Index Only Scan using tenk1_unique1 on public.tenk1 t
+ Output: (SubPlan 1)
+ SubPlan 1
+ -> Index Only Scan using tenk1_unique1 on public.tenk1
+ Output: t.unique1
+ Index Cond: (tenk1.unique1 = t.unique1)
+(11 rows)
explain (costs off, verbose) select t.unique1
from tenk1 t
where t.unique1 = (select t.unique1 from tenk1 where tenk1.unique1 = t.unique1);
- QUERY PLAN
--------------------------------------------------------------
- Seq Scan on public.tenk1 t
+ QUERY PLAN
+----------------------------------------------------------------------
+ Gather
Output: t.unique1
- Filter: (t.unique1 = (SubPlan 1))
- SubPlan 1
- -> Index Only Scan using tenk1_unique1 on public.tenk1
- Output: t.unique1
- Index Cond: (tenk1.unique1 = t.unique1)
-(7 rows)
+ Workers Planned: 4
+ -> Parallel Index Only Scan using tenk1_unique1 on public.tenk1 t
+ Output: t.unique1
+ Filter: (t.unique1 = (SubPlan 1))
+ SubPlan 1
+ -> Index Only Scan using tenk1_unique1 on public.tenk1
+ Output: t.unique1
+ Index Cond: (tenk1.unique1 = t.unique1)
+(10 rows)
explain (costs off, verbose) select *
from tenk1 t
order by (select t.unique1 from tenk1 where tenk1.unique1 = t.unique1);
- QUERY PLAN
-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
- Sort
+ QUERY PLAN
+----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
+ Gather Merge
Output: t.unique1, t.unique2, t.two, t.four, t.ten, t.twenty, t.hundred, t.thousand, t.twothousand, t.fivethous, t.tenthous, t.odd, t.even, t.stringu1, t.stringu2, t.string4, ((SubPlan 1))
- Sort Key: ((SubPlan 1))
- -> Gather
- Output: t.unique1, t.unique2, t.two, t.four, t.ten, t.twenty, t.hundred, t.thousand, t.twothousand, t.fivethous, t.tenthous, t.odd, t.even, t.stringu1, t.stringu2, t.string4, (SubPlan 1)
- Workers Planned: 4
+ Workers Planned: 4
+ -> Sort
+ Output: t.unique1, t.unique2, t.two, t.four, t.ten, t.twenty, t.hundred, t.thousand, t.twothousand, t.fivethous, t.tenthous, t.odd, t.even, t.stringu1, t.stringu2, t.string4, ((SubPlan 1))
+ Sort Key: ((SubPlan 1))
-> Parallel Seq Scan on public.tenk1 t
- Output: t.unique1, t.unique2, t.two, t.four, t.ten, t.twenty, t.hundred, t.thousand, t.twothousand, t.fivethous, t.tenthous, t.odd, t.even, t.stringu1, t.stringu2, t.string4
- SubPlan 1
- -> Index Only Scan using tenk1_unique1 on public.tenk1
- Output: t.unique1
- Index Cond: (tenk1.unique1 = t.unique1)
+ Output: t.unique1, t.unique2, t.two, t.four, t.ten, t.twenty, t.hundred, t.thousand, t.twothousand, t.fivethous, t.tenthous, t.odd, t.even, t.stringu1, t.stringu2, t.string4, (SubPlan 1)
+ SubPlan 1
+ -> Index Only Scan using tenk1_unique1 on public.tenk1
+ Output: t.unique1
+ Index Cond: (tenk1.unique1 = t.unique1)
(12 rows)
-- test subplan in join/lateral join
@@ -409,14 +415,14 @@ explain (costs off, verbose, timing off) select t.unique1, l.*
QUERY PLAN
----------------------------------------------------------------------
Gather
- Output: t.unique1, (SubPlan 1)
+ Output: t.unique1, ((SubPlan 1))
Workers Planned: 4
-> Parallel Index Only Scan using tenk1_unique1 on public.tenk1 t
- Output: t.unique1
- SubPlan 1
- -> Index Only Scan using tenk1_unique1 on public.tenk1
- Output: t.unique1
- Index Cond: (tenk1.unique1 = t.unique1)
+ Output: t.unique1, (SubPlan 1)
+ SubPlan 1
+ -> Index Only Scan using tenk1_unique1 on public.tenk1
+ Output: t.unique1
+ Index Cond: (tenk1.unique1 = t.unique1)
(9 rows)
-- can't put a gather at the top of a subplan that takes a param
@@ -1349,9 +1355,12 @@ SELECT 1 FROM tenk1_vw_sec
Workers Planned: 4
-> Parallel Index Only Scan using tenk1_unique1 on tenk1
SubPlan 1
- -> Aggregate
- -> Seq Scan on int4_tbl
- Filter: (f1 < tenk1_vw_sec.unique1)
-(9 rows)
+ -> Finalize Aggregate
+ -> Gather
+ Workers Planned: 1
+ -> Partial Aggregate
+ -> Parallel Seq Scan on int4_tbl
+ Filter: (f1 < tenk1_vw_sec.unique1)
+(12 rows)
rollback;
--
2.39.2 (Apple Git-143)
[application/octet-stream] v11-0001-Add-tests-before-change.patch (9.2K, ../../CAAaqYe8F=TNEF7Dk98dgLkksBt9T0QweTZ4kfif9+q5MKtxQ0Q@mail.gmail.com/3-v11-0001-Add-tests-before-change.patch)
download | inline diff:
From 931e64c7e2e2f819f35b5c7878d1c04ae14d9853 Mon Sep 17 00:00:00 2001
From: jcoleman <[email protected]>
Date: Mon, 26 Sep 2022 20:30:23 -0400
Subject: [PATCH v11 1/2] Add tests before change
---
src/test/regress/expected/select_parallel.out | 136 ++++++++++++++++++
src/test/regress/sql/select_parallel.sql | 32 +++++
2 files changed, 168 insertions(+)
diff --git a/src/test/regress/expected/select_parallel.out b/src/test/regress/expected/select_parallel.out
index d88353d496..0ddcf8e0b1 100644
--- a/src/test/regress/expected/select_parallel.out
+++ b/src/test/regress/expected/select_parallel.out
@@ -311,6 +311,142 @@ select count(*) from tenk1 where (two, four) not in
10000
(1 row)
+-- test parallel plans for queries containing correlated subplans
+-- where the subplan only needs params available from the current
+-- worker's scan.
+explain (costs off, verbose) select
+ (select t.unique1 from tenk1 where tenk1.unique1 = t.unique1)
+ from tenk1 t, generate_series(1, 10);
+ QUERY PLAN
+----------------------------------------------------------------------------
+ Gather
+ Output: (SubPlan 1)
+ Workers Planned: 4
+ -> Nested Loop
+ Output: t.unique1
+ -> Parallel Index Only Scan using tenk1_unique1 on public.tenk1 t
+ Output: t.unique1
+ -> Function Scan on pg_catalog.generate_series
+ Output: generate_series.generate_series
+ Function Call: generate_series(1, 10)
+ SubPlan 1
+ -> Index Only Scan using tenk1_unique1 on public.tenk1
+ Output: t.unique1
+ Index Cond: (tenk1.unique1 = t.unique1)
+(14 rows)
+
+explain (costs off, verbose) select
+ (select t.unique1 from tenk1 where tenk1.unique1 = t.unique1)
+ from tenk1 t;
+ QUERY PLAN
+----------------------------------------------------------------------
+ Gather
+ Output: (SubPlan 1)
+ Workers Planned: 4
+ -> Parallel Index Only Scan using tenk1_unique1 on public.tenk1 t
+ Output: t.unique1
+ SubPlan 1
+ -> Index Only Scan using tenk1_unique1 on public.tenk1
+ Output: t.unique1
+ Index Cond: (tenk1.unique1 = t.unique1)
+(9 rows)
+
+explain (costs off, verbose) select
+ (select t.unique1 from tenk1 where tenk1.unique1 = t.unique1)
+ from tenk1 t
+ limit 1;
+ QUERY PLAN
+-------------------------------------------------------------------
+ Limit
+ Output: ((SubPlan 1))
+ -> Seq Scan on public.tenk1 t
+ Output: (SubPlan 1)
+ SubPlan 1
+ -> Index Only Scan using tenk1_unique1 on public.tenk1
+ Output: t.unique1
+ Index Cond: (tenk1.unique1 = t.unique1)
+(8 rows)
+
+explain (costs off, verbose) select t.unique1
+ from tenk1 t
+ where t.unique1 = (select t.unique1 from tenk1 where tenk1.unique1 = t.unique1);
+ QUERY PLAN
+-------------------------------------------------------------
+ Seq Scan on public.tenk1 t
+ Output: t.unique1
+ Filter: (t.unique1 = (SubPlan 1))
+ SubPlan 1
+ -> Index Only Scan using tenk1_unique1 on public.tenk1
+ Output: t.unique1
+ Index Cond: (tenk1.unique1 = t.unique1)
+(7 rows)
+
+explain (costs off, verbose) select *
+ from tenk1 t
+ order by (select t.unique1 from tenk1 where tenk1.unique1 = t.unique1);
+ QUERY PLAN
+----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
+ Sort
+ Output: t.unique1, t.unique2, t.two, t.four, t.ten, t.twenty, t.hundred, t.thousand, t.twothousand, t.fivethous, t.tenthous, t.odd, t.even, t.stringu1, t.stringu2, t.string4, ((SubPlan 1))
+ Sort Key: ((SubPlan 1))
+ -> Gather
+ Output: t.unique1, t.unique2, t.two, t.four, t.ten, t.twenty, t.hundred, t.thousand, t.twothousand, t.fivethous, t.tenthous, t.odd, t.even, t.stringu1, t.stringu2, t.string4, (SubPlan 1)
+ Workers Planned: 4
+ -> Parallel Seq Scan on public.tenk1 t
+ Output: t.unique1, t.unique2, t.two, t.four, t.ten, t.twenty, t.hundred, t.thousand, t.twothousand, t.fivethous, t.tenthous, t.odd, t.even, t.stringu1, t.stringu2, t.string4
+ SubPlan 1
+ -> Index Only Scan using tenk1_unique1 on public.tenk1
+ Output: t.unique1
+ Index Cond: (tenk1.unique1 = t.unique1)
+(12 rows)
+
+-- test subplan in join/lateral join
+explain (costs off, verbose, timing off) select t.unique1, l.*
+ from tenk1 t
+ join lateral (
+ select (select t.unique1 from tenk1 where tenk1.unique1 = t.unique1 offset 0)
+ ) l on true;
+ QUERY PLAN
+----------------------------------------------------------------------
+ Gather
+ Output: t.unique1, (SubPlan 1)
+ Workers Planned: 4
+ -> Parallel Index Only Scan using tenk1_unique1 on public.tenk1 t
+ Output: t.unique1
+ SubPlan 1
+ -> Index Only Scan using tenk1_unique1 on public.tenk1
+ Output: t.unique1
+ Index Cond: (tenk1.unique1 = t.unique1)
+(9 rows)
+
+-- can't put a gather at the top of a subplan that takes a param
+explain (costs off, verbose) select * from tenk1 t where t.two in (
+ select t.two
+ from tenk1
+ join tenk1 t3 on t3.stringu1 = tenk1.stringu1
+ where tenk1.four = t.four
+);
+ QUERY PLAN
+---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
+ Seq Scan on public.tenk1 t
+ Output: t.unique1, t.unique2, t.two, t.four, t.ten, t.twenty, t.hundred, t.thousand, t.twothousand, t.fivethous, t.tenthous, t.odd, t.even, t.stringu1, t.stringu2, t.string4
+ Filter: (SubPlan 1)
+ SubPlan 1
+ -> Hash Join
+ Output: t.two
+ Hash Cond: (tenk1.stringu1 = t3.stringu1)
+ -> Seq Scan on public.tenk1
+ Output: tenk1.unique1, tenk1.unique2, tenk1.two, tenk1.four, tenk1.ten, tenk1.twenty, tenk1.hundred, tenk1.thousand, tenk1.twothousand, tenk1.fivethous, tenk1.tenthous, tenk1.odd, tenk1.even, tenk1.stringu1, tenk1.stringu2, tenk1.string4
+ Filter: (tenk1.four = t.four)
+ -> Hash
+ Output: t3.stringu1
+ -> Gather
+ Output: t3.stringu1
+ Workers Planned: 4
+ -> Parallel Seq Scan on public.tenk1 t3
+ Output: t3.stringu1
+(17 rows)
+
-- this is not parallel-safe due to use of random() within SubLink's testexpr:
explain (costs off)
select * from tenk1 where (unique1 + random())::integer not in
diff --git a/src/test/regress/sql/select_parallel.sql b/src/test/regress/sql/select_parallel.sql
index 80c914dc02..c6908cb919 100644
--- a/src/test/regress/sql/select_parallel.sql
+++ b/src/test/regress/sql/select_parallel.sql
@@ -111,6 +111,38 @@ explain (costs off)
(select hundred, thousand from tenk2 where thousand > 100);
select count(*) from tenk1 where (two, four) not in
(select hundred, thousand from tenk2 where thousand > 100);
+-- test parallel plans for queries containing correlated subplans
+-- where the subplan only needs params available from the current
+-- worker's scan.
+explain (costs off, verbose) select
+ (select t.unique1 from tenk1 where tenk1.unique1 = t.unique1)
+ from tenk1 t, generate_series(1, 10);
+explain (costs off, verbose) select
+ (select t.unique1 from tenk1 where tenk1.unique1 = t.unique1)
+ from tenk1 t;
+explain (costs off, verbose) select
+ (select t.unique1 from tenk1 where tenk1.unique1 = t.unique1)
+ from tenk1 t
+ limit 1;
+explain (costs off, verbose) select t.unique1
+ from tenk1 t
+ where t.unique1 = (select t.unique1 from tenk1 where tenk1.unique1 = t.unique1);
+explain (costs off, verbose) select *
+ from tenk1 t
+ order by (select t.unique1 from tenk1 where tenk1.unique1 = t.unique1);
+-- test subplan in join/lateral join
+explain (costs off, verbose, timing off) select t.unique1, l.*
+ from tenk1 t
+ join lateral (
+ select (select t.unique1 from tenk1 where tenk1.unique1 = t.unique1 offset 0)
+ ) l on true;
+-- can't put a gather at the top of a subplan that takes a param
+explain (costs off, verbose) select * from tenk1 t where t.two in (
+ select t.two
+ from tenk1
+ join tenk1 t3 on t3.stringu1 = tenk1.stringu1
+ where tenk1.four = t.four
+);
-- this is not parallel-safe due to use of random() within SubLink's testexpr:
explain (costs off)
select * from tenk1 where (unique1 + random())::integer not in
--
2.39.2 (Apple Git-143)
^ permalink raw reply [nested|flat] 35+ messages in thread
* Re: Parallelize correlated subqueries that execute within each worker
@ 2024-01-09 07:08 vignesh C <[email protected]>
parent: James Coleman <[email protected]>
0 siblings, 2 replies; 35+ messages in thread
From: vignesh C @ 2024-01-09 07:08 UTC (permalink / raw)
To: James Coleman <[email protected]>; +Cc: Richard Guo <[email protected]>; Tomas Vondra <[email protected]>; Andres Freund <[email protected]>; Robert Haas <[email protected]>; pgsql-hackers; Amit Kapila <[email protected]>; Tom Lane <[email protected]>
On Tue, 4 Jul 2023 at 06:56, James Coleman <[email protected]> wrote:
>
> On Sun, Jun 11, 2023 at 10:23 PM James Coleman <[email protected]> wrote:
> >
> > ...
> > > And while trying the v9 patch I came across a crash with the query
> > > below.
> > >
> > > set min_parallel_table_scan_size to 0;
> > > set parallel_setup_cost to 0;
> > > set parallel_tuple_cost to 0;
> > >
> > > explain (costs off)
> > > select * from pg_description t1 where objoid in
> > > (select objoid from pg_description t2 where t2.description = t1.description);
> > > QUERY PLAN
> > > --------------------------------------------------------
> > > Seq Scan on pg_description t1
> > > Filter: (SubPlan 1)
> > > SubPlan 1
> > > -> Gather
> > > Workers Planned: 2
> > > -> Parallel Seq Scan on pg_description t2
> > > Filter: (description = t1.description)
> > > (7 rows)
> > >
> > > select * from pg_description t1 where objoid in
> > > (select objoid from pg_description t2 where t2.description = t1.description);
> > > WARNING: terminating connection because of crash of another server process
> > >
> > > Seems something is wrong when extracting the argument from the Param in
> > > parallel worker.
> >
> > With what I'm trying to change I don't think this plan should ever be
> > generated since it means we'd have to pass a param from the outer seq
> > scan into the parallel subplan, which we can't do (currently).
> >
> > I've attached the full backtrace to the email, but as you hinted at
> > the parallel worker is trying to get the param (in this case
> > detoasting it), but the param doesn't exist on the worker, so it seg
> > faults. Looking at this further I think there's an existing test case
> > that exposes the misplanning here (the one right under the comment
> > "Parallel Append is not to be used when the subpath depends on the
> > outer param" in select_parallel.sql), but it doesn't seg fault because
> > the param is an integer, doesn't need to be detoasted, and therefore
> > (I think) we skate by (but probably with wrong results in depending on
> > the dataset).
> >
> > Interestingly this is one of the existing test queries my original
> > patch approach didn't change, so this gives me something specific to
> > work with improving the path. Thanks for testing this and bringing
> > this to my attention!
>
> Here's what I've found debugging this:
>
> There's only a single gather path ever created when planning this
> query, making it easy to know which one is the problem. That gather
> path is created with this stacktrace:
>
> frame #0: 0x0000000105291590
> postgres`create_gather_path(root=0x000000013081ae78,
> rel=0x000000013080c8e8, subpath=0x000000013081c080,
> target=0x000000013081c8c0, required_outer=0x0000000000000000,
> rows=0x0000000000000000) at pathnode.c:1971:2
> frame #1: 0x0000000105208e54
> postgres`generate_gather_paths(root=0x000000013081ae78,
> rel=0x000000013080c8e8, override_rows=false) at allpaths.c:3097:4
> frame #2: 0x00000001052090ec
> postgres`generate_useful_gather_paths(root=0x000000013081ae78,
> rel=0x000000013080c8e8, override_rows=false) at allpaths.c:3241:2
> frame #3: 0x0000000105258754
> postgres`apply_scanjoin_target_to_paths(root=0x000000013081ae78,
> rel=0x000000013080c8e8, scanjoin_targets=0x000000013081c978,
> scanjoin_targets_contain_srfs=0x0000000000000000,
> scanjoin_target_parallel_safe=true, tlist_same_exprs=true) at
> planner.c:7696:3
> frame #4: 0x00000001052533cc
> postgres`grouping_planner(root=0x000000013081ae78, tuple_fraction=0.5)
> at planner.c:1611:3
> frame #5: 0x0000000105251e9c
> postgres`subquery_planner(glob=0x00000001308188d8,
> parse=0x000000013080caf8, parent_root=0x000000013080cc38,
> hasRecursion=false, tuple_fraction=0.5) at planner.c:1062:2
> frame #6: 0x000000010526b134
> postgres`make_subplan(root=0x000000013080cc38,
> orig_subquery=0x000000013080ff58, subLinkType=ANY_SUBLINK,
> subLinkId=0, testexpr=0x000000013080d848, isTopQual=true) at
> subselect.c:221:12
> frame #7: 0x0000000105268b8c
> postgres`process_sublinks_mutator(node=0x000000013080d6d8,
> context=0x000000016b0998f8) at subselect.c:1950:10
> frame #8: 0x0000000105268ad8
> postgres`SS_process_sublinks(root=0x000000013080cc38,
> expr=0x000000013080d6d8, isQual=true) at subselect.c:1923:9
> frame #9: 0x00000001052527b8
> postgres`preprocess_expression(root=0x000000013080cc38,
> expr=0x000000013080d6d8, kind=0) at planner.c:1169:10
> frame #10: 0x0000000105252954
> postgres`preprocess_qual_conditions(root=0x000000013080cc38,
> jtnode=0x000000013080d108) at planner.c:1214:14
> frame #11: 0x0000000105251580
> postgres`subquery_planner(glob=0x00000001308188d8,
> parse=0x0000000137010d68, parent_root=0x0000000000000000,
> hasRecursion=false, tuple_fraction=0) at planner.c:832:2
> frame #12: 0x000000010525042c
> postgres`standard_planner(parse=0x0000000137010d68,
> query_string="explain (costs off)\nselect * from pg_description t1
> where objoid in\n (select objoid from pg_description t2 where
> t2.description = t1.description);", cursorOptions=2048,
> boundParams=0x0000000000000000) at planner.c:411:9
>
> There aren't any lateral markings on the rels. Additionally the
> partial path has param_info=null (I found out from Tom in a separate
> thread [1] that this is only set for outer relations from the same
> query level).
>
> The only param that I could easily find at first was a single param of
> type PARAM_EXTERN in root->plan_params in make_subplan().
>
> I spent a lot of time trying to figure out where we could find the
> PARAM_EXEC param that's being fed into the subplan, but it doesn't
> seem like we have access to any of these things at the point in the
> path creation process that it's interesting to us when inserting the
> gather nodes.
>
> Given all of that I settled on this approach:
> 1. Modify is_parallel_safe() to by default ignore PARAM_EXEC params.
> 2. Add is_parallel_safe_with_params() that checks for the existence of
> such params.
> 3. Store the required params in a bitmapset on each base rel.
> 4. Union the bitmapset on join rels.
> 5. Only insert a gather node if that bitmapset is empty.
>
> I have an intuition that there's some spot (e.g. joins) that we should
> be removing params from this set (e.g., when we've satisfied them),
> but I haven't been able to come up with such a scenario as yet.
>
> The attached v11 fixes the issue you reported.
One of the tests has failed in CFBot at [1] with:
+++ /tmp/cirrus-ci-build/build/testrun/pg_upgrade/002_pg_upgrade/data/results/select_parallel.out
2023-12-20 20:08:42.480004000 +0000
@@ -137,23 +137,24 @@
explain (costs off)
select (select max((select pa1.b from part_pa_test pa1 where pa1.a = pa2.a)))
from part_pa_test pa2;
- QUERY PLAN
---------------------------------------------------------------
- Aggregate
+ QUERY PLAN
+--------------------------------------------------------------------
+ Finalize Aggregate
-> Gather
Workers Planned: 3
- -> Parallel Append
- -> Parallel Seq Scan on part_pa_test_p1 pa2_1
- -> Parallel Seq Scan on part_pa_test_p2 pa2_2
+ -> Partial Aggregate
+ -> Parallel Append
+ -> Parallel Seq Scan on part_pa_test_p1 pa2_1
+ -> Parallel Seq Scan on part_pa_test_p2 pa2_2
+ SubPlan 1
+ -> Append
+ -> Seq Scan on part_pa_test_p1 pa1_1
+ Filter: (a = pa2.a)
+ -> Seq Scan on part_pa_test_p2 pa1_2
+ Filter: (a = pa2.a)
SubPlan 2
-> Result
- SubPlan 1
- -> Append
- -> Seq Scan on part_pa_test_p1 pa1_1
- Filter: (a = pa2.a)
- -> Seq Scan on part_pa_test_p2 pa1_2
- Filter: (a = pa2.a)
-(14 rows)
+(15 rows)
More details of the failure is available at [2].
[1] - https://cirrus-ci.com/task/5685696451575808
[2] - https://api.cirrus-ci.com/v1/artifact/task/5685696451575808/testrun/build/testrun/pg_upgrade/002_pg_...
Regards,
Vignesh
^ permalink raw reply [nested|flat] 35+ messages in thread
* Re: Parallelize correlated subqueries that execute within each worker
@ 2024-01-23 14:33 Akshat Jaimini <[email protected]>
parent: vignesh C <[email protected]>
1 sibling, 1 reply; 35+ messages in thread
From: Akshat Jaimini @ 2024-01-23 14:33 UTC (permalink / raw)
To: [email protected]; +Cc: James Coleman <[email protected]>
Hello!
I was going through the previous conversations for this particular patch and it seems that this patch failed some tests previously?
Imo we should move it to the next CF so that the remaining issues can be resolved accordingly.
^ permalink raw reply [nested|flat] 35+ messages in thread
* Re: Parallelize correlated subqueries that execute within each worker
@ 2024-01-23 20:20 Robert Haas <[email protected]>
parent: Akshat Jaimini <[email protected]>
0 siblings, 1 reply; 35+ messages in thread
From: Robert Haas @ 2024-01-23 20:20 UTC (permalink / raw)
To: Akshat Jaimini <[email protected]>; +Cc: [email protected]; James Coleman <[email protected]>
On Tue, Jan 23, 2024 at 9:34 AM Akshat Jaimini <[email protected]> wrote:
> Hello!
> I was going through the previous conversations for this particular patch and it seems that this patch failed some tests previously?
> Imo we should move it to the next CF so that the remaining issues can be resolved accordingly.
So I guess the question here is whether this is thought to be ready
for serious review or whether it is still thought to need work. If the
latter, it should be marked RwF until that happens -- if the former,
then we should try to review it rather than letting it languish
forever.
--
Robert Haas
EDB: http://www.enterprisedb.com
^ permalink raw reply [nested|flat] 35+ messages in thread
* Re: Parallelize correlated subqueries that execute within each worker
@ 2024-01-30 16:16 Akshat Jaimini <[email protected]>
parent: Robert Haas <[email protected]>
0 siblings, 1 reply; 35+ messages in thread
From: Akshat Jaimini @ 2024-01-30 16:16 UTC (permalink / raw)
To: [email protected]; +Cc: James Coleman <[email protected]>
I think we should move this patch to the next CF as I believe that work is still going on resolving the last reported bug.
^ permalink raw reply [nested|flat] 35+ messages in thread
* Re: Parallelize correlated subqueries that execute within each worker
@ 2024-01-30 16:54 Robert Haas <[email protected]>
parent: Akshat Jaimini <[email protected]>
0 siblings, 1 reply; 35+ messages in thread
From: Robert Haas @ 2024-01-30 16:54 UTC (permalink / raw)
To: Akshat Jaimini <[email protected]>; +Cc: [email protected]; James Coleman <[email protected]>
On Tue, Jan 30, 2024 at 11:17 AM Akshat Jaimini <[email protected]> wrote:
> I think we should move this patch to the next CF as I believe that work is still going on resolving the last reported bug.
We shouldn't just keep pushing this forward to the next CF. It's been
idle since July. If it needs more work, mark it RwF and it can be
reopened when there's something for a reviewer to do.
--
Robert Haas
EDB: http://www.enterprisedb.com
^ permalink raw reply [nested|flat] 35+ messages in thread
* Re: Parallelize correlated subqueries that execute within each worker
@ 2024-01-31 02:51 James Coleman <[email protected]>
parent: vignesh C <[email protected]>
1 sibling, 1 reply; 35+ messages in thread
From: James Coleman @ 2024-01-31 02:51 UTC (permalink / raw)
To: vignesh C <[email protected]>; +Cc: Richard Guo <[email protected]>; Tomas Vondra <[email protected]>; Andres Freund <[email protected]>; Robert Haas <[email protected]>; pgsql-hackers; Amit Kapila <[email protected]>; Tom Lane <[email protected]>
On Tue, Jan 9, 2024 at 2:09 AM vignesh C <[email protected]> wrote:
> ...
> > Given all of that I settled on this approach:
> > 1. Modify is_parallel_safe() to by default ignore PARAM_EXEC params.
> > 2. Add is_parallel_safe_with_params() that checks for the existence of
> > such params.
> > 3. Store the required params in a bitmapset on each base rel.
> > 4. Union the bitmapset on join rels.
> > 5. Only insert a gather node if that bitmapset is empty.
> >
> > I have an intuition that there's some spot (e.g. joins) that we should
> > be removing params from this set (e.g., when we've satisfied them),
> > but I haven't been able to come up with such a scenario as yet.
> >
> > The attached v11 fixes the issue you reported.
>
> One of the tests has failed in CFBot at [1] with:
> +++ /tmp/cirrus-ci-build/build/testrun/pg_upgrade/002_pg_upgrade/data/results/select_parallel.out
> 2023-12-20 20:08:42.480004000 +0000
> @@ -137,23 +137,24 @@
> explain (costs off)
> select (select max((select pa1.b from part_pa_test pa1 where pa1.a = pa2.a)))
> from part_pa_test pa2;
> - QUERY PLAN
> ---------------------------------------------------------------
> - Aggregate
> + QUERY PLAN
> +--------------------------------------------------------------------
> + Finalize Aggregate
> -> Gather
> Workers Planned: 3
> - -> Parallel Append
> - -> Parallel Seq Scan on part_pa_test_p1 pa2_1
> - -> Parallel Seq Scan on part_pa_test_p2 pa2_2
> + -> Partial Aggregate
> + -> Parallel Append
> + -> Parallel Seq Scan on part_pa_test_p1 pa2_1
> + -> Parallel Seq Scan on part_pa_test_p2 pa2_2
> + SubPlan 1
> + -> Append
> + -> Seq Scan on part_pa_test_p1 pa1_1
> + Filter: (a = pa2.a)
> + -> Seq Scan on part_pa_test_p2 pa1_2
> + Filter: (a = pa2.a)
> SubPlan 2
> -> Result
> - SubPlan 1
> - -> Append
> - -> Seq Scan on part_pa_test_p1 pa1_1
> - Filter: (a = pa2.a)
> - -> Seq Scan on part_pa_test_p2 pa1_2
> - Filter: (a = pa2.a)
> -(14 rows)
> +(15 rows)
>
> More details of the failure is available at [2].
>
> [1] - https://cirrus-ci.com/task/5685696451575808
> [2] - https://api.cirrus-ci.com/v1/artifact/task/5685696451575808/testrun/build/testrun/pg_upgrade/002_pg_...
Thanks for noting this here.
I've finally had a chance to look at this, and I don't believe there's
any real failure here, merely drift of how the planner works on master
resulting in this query now being eligible for a different plan shape.
I was a bit wary at first because the changing test query is one I'd
previously referenced in [1] as likely exposing the bug I'd fixed
where params where being used across worker boundaries. However
looking at the diff in the patch at that point (v10) that particular
test query formed a different plan shape (there were two gather nodes
being created, and params crossing between them).
But in the current revision of master with the current patch applied
that's no longer true: we have a Gather node, and the Subplan using
the param is properly under that Gather node, and the param should be
being both generated and consumed within the same worker process.
So I've updated the patch to show that plan change as part of the diff.
See attached v12
Regards,
James Coleman
1: https://www.postgresql.org/message-id/CAAaqYe-_TObm5KwmZLYXBJ3BJGh4cUZWM0v1mY1gWTMkRNQXDQ%40mail.gma...
Attachments:
[application/octet-stream] v12-0002-Parallelize-correlated-subqueries.patch (31.3K, ../../CAAaqYe-Ld1q_b9pOf0PRjfQLWCgdkTvnopfeXgmrSvEQu0Ox=A@mail.gmail.com/2-v12-0002-Parallelize-correlated-subqueries.patch)
download | inline diff:
From ac42a4080e002627af2c221591d7c872612a7ce7 Mon Sep 17 00:00:00 2001
From: jcoleman <[email protected]>
Date: Sun, 2 Jul 2023 15:23:49 -0400
Subject: [PATCH v12 2/2] Parallelize correlated subqueries
When params are provided at the current query level (i.e., are generated
within a single worker and not shared across workers) we can safely
execute these in parallel.
We accomplish this by tracking the PARAM_EXEC params that are needed for
a rel to be safely executed in parallel and only inserting a Gather node
if that set is empty.
---
doc/src/sgml/parallel.sgml | 3 +-
src/backend/optimizer/path/allpaths.c | 24 ++-
src/backend/optimizer/util/clauses.c | 73 ++++++--
src/backend/optimizer/util/relnode.c | 1 +
src/include/nodes/pathnodes.h | 6 +
src/include/optimizer/clauses.h | 1 +
.../regress/expected/incremental_sort.out | 41 ++---
src/test/regress/expected/partition_prune.out | 104 +++++------
src/test/regress/expected/select_parallel.out | 161 ++++++++++--------
src/test/regress/sql/select_parallel.sql | 8 +-
10 files changed, 266 insertions(+), 156 deletions(-)
diff --git a/doc/src/sgml/parallel.sgml b/doc/src/sgml/parallel.sgml
index 5acc9537d6..fd32572ec8 100644
--- a/doc/src/sgml/parallel.sgml
+++ b/doc/src/sgml/parallel.sgml
@@ -518,7 +518,8 @@ EXPLAIN SELECT * FROM pgbench_accounts WHERE filler LIKE '%x%';
<listitem>
<para>
- Plan nodes that reference a correlated <literal>SubPlan</literal>.
+ Plan nodes that reference a correlated <literal>SubPlan</literal> where
+ the result is shared between workers.
</para>
</listitem>
</itemizedlist>
diff --git a/src/backend/optimizer/path/allpaths.c b/src/backend/optimizer/path/allpaths.c
index 84c4de488a..37c44d393b 100644
--- a/src/backend/optimizer/path/allpaths.c
+++ b/src/backend/optimizer/path/allpaths.c
@@ -632,7 +632,7 @@ set_rel_consider_parallel(PlannerInfo *root, RelOptInfo *rel,
if (proparallel != PROPARALLEL_SAFE)
return;
- if (!is_parallel_safe(root, (Node *) rte->tablesample->args))
+ if (!is_parallel_safe_with_params(root, (Node *) rte->tablesample->args, &rel->params_req_for_parallel))
return;
}
@@ -698,7 +698,7 @@ set_rel_consider_parallel(PlannerInfo *root, RelOptInfo *rel,
case RTE_FUNCTION:
/* Check for parallel-restricted functions. */
- if (!is_parallel_safe(root, (Node *) rte->functions))
+ if (!is_parallel_safe_with_params(root, (Node *) rte->functions, &rel->params_req_for_parallel))
return;
break;
@@ -708,7 +708,7 @@ set_rel_consider_parallel(PlannerInfo *root, RelOptInfo *rel,
case RTE_VALUES:
/* Check for parallel-restricted functions. */
- if (!is_parallel_safe(root, (Node *) rte->values_lists))
+ if (!is_parallel_safe_with_params(root, (Node *) rte->values_lists, &rel->params_req_for_parallel))
return;
break;
@@ -745,14 +745,14 @@ set_rel_consider_parallel(PlannerInfo *root, RelOptInfo *rel,
* outer join clauses work correctly. It would likely break equivalence
* classes, too.
*/
- if (!is_parallel_safe(root, (Node *) rel->baserestrictinfo))
+ if (!is_parallel_safe_with_params(root, (Node *) rel->baserestrictinfo, &rel->params_req_for_parallel))
return;
/*
* Likewise, if the relation's outputs are not parallel-safe, give up.
* (Usually, they're just Vars, but sometimes they're not.)
*/
- if (!is_parallel_safe(root, (Node *) rel->reltarget->exprs))
+ if (!is_parallel_safe_with_params(root, (Node *) rel->reltarget->exprs, &rel->params_req_for_parallel))
return;
/* We have a winner. */
@@ -3071,6 +3071,13 @@ generate_gather_paths(PlannerInfo *root, RelOptInfo *rel, bool override_rows)
if (rel->partial_pathlist == NIL)
return;
+ /*
+ * Wait to insert Gather nodes until all PARAM_EXEC params are provided
+ * within the current rel since we can't pass them to workers.
+ */
+ if (!bms_is_empty(rel->params_req_for_parallel))
+ return;
+
/* Should we override the rel's rowcount estimate? */
if (override_rows)
rowsp = &rows;
@@ -3209,6 +3216,13 @@ generate_useful_gather_paths(PlannerInfo *root, RelOptInfo *rel, bool override_r
if (rel->partial_pathlist == NIL)
return;
+ /*
+ * Wait to insert Gather nodes until all PARAM_EXEC params are provided
+ * within the current rel since we can't pass them to workers.
+ */
+ if (!bms_is_empty(rel->params_req_for_parallel))
+ return;
+
/* Should we override the rel's rowcount estimate? */
if (override_rows)
rowsp = &rows;
diff --git a/src/backend/optimizer/util/clauses.c b/src/backend/optimizer/util/clauses.c
index 94eb56a1e7..9acad18154 100644
--- a/src/backend/optimizer/util/clauses.c
+++ b/src/backend/optimizer/util/clauses.c
@@ -91,6 +91,8 @@ typedef struct
{
char max_hazard; /* worst proparallel hazard found so far */
char max_interesting; /* worst proparallel hazard of interest */
+ bool check_params;
+ Bitmapset **required_params;
List *safe_param_ids; /* PARAM_EXEC Param IDs to treat as safe */
} max_parallel_hazard_context;
@@ -720,6 +722,7 @@ max_parallel_hazard(Query *parse)
context.max_hazard = PROPARALLEL_SAFE;
context.max_interesting = PROPARALLEL_UNSAFE;
+ context.check_params = true;
context.safe_param_ids = NIL;
(void) max_parallel_hazard_walker((Node *) parse, &context);
return context.max_hazard;
@@ -736,8 +739,6 @@ bool
is_parallel_safe(PlannerInfo *root, Node *node)
{
max_parallel_hazard_context context;
- PlannerInfo *proot;
- ListCell *l;
/*
* Even if the original querytree contained nothing unsafe, we need to
@@ -751,6 +752,43 @@ is_parallel_safe(PlannerInfo *root, Node *node)
/* Else use max_parallel_hazard's search logic, but stop on RESTRICTED */
context.max_hazard = PROPARALLEL_SAFE;
context.max_interesting = PROPARALLEL_RESTRICTED;
+ context.check_params = false;
+ context.required_params = NULL;
+
+ return !max_parallel_hazard_walker(node, &context);
+}
+
+/*
+ * is_parallel_safe_with_params
+ * As above, but additionally tracking what PARAM_EXEC params required to
+ * be provided within a worker for a gather to be inserted at this level
+ * of the query. Those required params are passed to the caller through
+ * the required_params argument.
+ *
+ * Note: required_params is only valid if node is otherwise parallel safe.
+ */
+bool
+is_parallel_safe_with_params(PlannerInfo *root, Node *node, Bitmapset **required_params)
+{
+ max_parallel_hazard_context context;
+ PlannerInfo *proot;
+ ListCell *l;
+
+ /*
+ * Even if the original querytree contained nothing unsafe, we need to
+ * search the expression if we have generated any PARAM_EXEC Params while
+ * planning, because those will have to be provided for the expression to
+ * remain parallel safe and there might be one in this expression. But
+ * otherwise we don't need to look.
+ */
+ if (root->glob->maxParallelHazard == PROPARALLEL_SAFE &&
+ root->glob->paramExecTypes == NIL)
+ return true;
+ /* Else use max_parallel_hazard's search logic, but stop on RESTRICTED */
+ context.max_hazard = PROPARALLEL_SAFE;
+ context.max_interesting = PROPARALLEL_RESTRICTED;
+ context.check_params = false;
+ context.required_params = required_params;
context.safe_param_ids = NIL;
/*
@@ -890,13 +928,22 @@ max_parallel_hazard_walker(Node *node, max_parallel_hazard_context *context)
if (!subplan->parallel_safe &&
max_parallel_hazard_test(PROPARALLEL_RESTRICTED, context))
return true;
- save_safe_param_ids = context->safe_param_ids;
- context->safe_param_ids = list_concat_copy(context->safe_param_ids,
- subplan->paramIds);
+
+ if (context->check_params || context->required_params != NULL)
+ {
+ save_safe_param_ids = context->safe_param_ids;
+ context->safe_param_ids = list_concat_copy(context->safe_param_ids,
+ subplan->paramIds);
+ }
if (max_parallel_hazard_walker(subplan->testexpr, context))
return true; /* no need to restore safe_param_ids */
- list_free(context->safe_param_ids);
- context->safe_param_ids = save_safe_param_ids;
+
+ if (context->check_params || context->required_params != NULL)
+ {
+ list_free(context->safe_param_ids);
+ context->safe_param_ids = save_safe_param_ids;
+ }
+
/* we must also check args, but no special Param treatment there */
if (max_parallel_hazard_walker((Node *) subplan->args, context))
return true;
@@ -915,14 +962,18 @@ max_parallel_hazard_walker(Node *node, max_parallel_hazard_context *context)
{
Param *param = (Param *) node;
- if (param->paramkind == PARAM_EXTERN)
+ if (param->paramkind != PARAM_EXEC || !(context->check_params || context->required_params != NULL))
return false;
- if (param->paramkind != PARAM_EXEC ||
- !list_member_int(context->safe_param_ids, param->paramid))
+ if (!list_member_int(context->safe_param_ids, param->paramid))
{
if (max_parallel_hazard_test(PROPARALLEL_RESTRICTED, context))
- return true;
+ {
+ if (context->required_params != NULL)
+ *context->required_params = bms_add_member(*context->required_params, param->paramid);
+ if (context->check_params)
+ return true;
+ }
}
return false; /* nothing to recurse to */
}
diff --git a/src/backend/optimizer/util/relnode.c b/src/backend/optimizer/util/relnode.c
index 22d01cef5b..58228ff269 100644
--- a/src/backend/optimizer/util/relnode.c
+++ b/src/backend/optimizer/util/relnode.c
@@ -699,6 +699,7 @@ build_join_rel(PlannerInfo *root,
joinrel->consider_startup = (root->tuple_fraction > 0);
joinrel->consider_param_startup = false;
joinrel->consider_parallel = false;
+ joinrel->params_req_for_parallel = bms_union(outer_rel->params_req_for_parallel, inner_rel->params_req_for_parallel);
joinrel->reltarget = create_empty_pathtarget();
joinrel->pathlist = NIL;
joinrel->ppilist = NIL;
diff --git a/src/include/nodes/pathnodes.h b/src/include/nodes/pathnodes.h
index 137da178dc..cb5721963d 100644
--- a/src/include/nodes/pathnodes.h
+++ b/src/include/nodes/pathnodes.h
@@ -871,6 +871,12 @@ typedef struct RelOptInfo
/* consider parallel paths? */
bool consider_parallel;
+ /*
+ * Params, if any, required to be provided when consider_parallel is true.
+ * Note: if consider_parallel is false then this is not meaningful.
+ */
+ Bitmapset *params_req_for_parallel;
+
/*
* default result targetlist for Paths scanning this relation; list of
* Vars/Exprs, cost, width
diff --git a/src/include/optimizer/clauses.h b/src/include/optimizer/clauses.h
index 34b301e537..eb4334f565 100644
--- a/src/include/optimizer/clauses.h
+++ b/src/include/optimizer/clauses.h
@@ -34,6 +34,7 @@ extern bool contain_subplans(Node *clause);
extern char max_parallel_hazard(Query *parse);
extern bool is_parallel_safe(PlannerInfo *root, Node *node);
+extern bool is_parallel_safe_with_params(PlannerInfo *root, Node *node, Bitmapset **required_params);
extern bool contain_nonstrict_functions(Node *clause);
extern bool contain_exec_param(Node *clause, List *param_ids);
extern bool contain_leaked_vars(Node *clause);
diff --git a/src/test/regress/expected/incremental_sort.out b/src/test/regress/expected/incremental_sort.out
index 7fdb685313..df1c52414e 100644
--- a/src/test/regress/expected/incremental_sort.out
+++ b/src/test/regress/expected/incremental_sort.out
@@ -1597,20 +1597,21 @@ explain (costs off) select distinct
unique1,
(select t.unique1 from tenk1 where tenk1.unique1 = t.unique1)
from tenk1 t, generate_series(1, 1000);
- QUERY PLAN
----------------------------------------------------------------------------------
+ QUERY PLAN
+---------------------------------------------------------------------------------------
Unique
- -> Sort
- Sort Key: t.unique1, ((SubPlan 1))
- -> Gather
- Workers Planned: 2
- -> Nested Loop
- -> Parallel Index Only Scan using tenk1_unique1 on tenk1 t
- -> Function Scan on generate_series
- SubPlan 1
- -> Index Only Scan using tenk1_unique1 on tenk1
- Index Cond: (unique1 = t.unique1)
-(11 rows)
+ -> Gather Merge
+ Workers Planned: 2
+ -> Unique
+ -> Sort
+ Sort Key: t.unique1, ((SubPlan 1))
+ -> Nested Loop
+ -> Parallel Index Only Scan using tenk1_unique1 on tenk1 t
+ -> Function Scan on generate_series
+ SubPlan 1
+ -> Index Only Scan using tenk1_unique1 on tenk1
+ Index Cond: (unique1 = t.unique1)
+(12 rows)
explain (costs off) select
unique1,
@@ -1619,16 +1620,16 @@ from tenk1 t, generate_series(1, 1000)
order by 1, 2;
QUERY PLAN
---------------------------------------------------------------------------
- Sort
- Sort Key: t.unique1, ((SubPlan 1))
- -> Gather
- Workers Planned: 2
+ Gather Merge
+ Workers Planned: 2
+ -> Sort
+ Sort Key: t.unique1, ((SubPlan 1))
-> Nested Loop
-> Parallel Index Only Scan using tenk1_unique1 on tenk1 t
-> Function Scan on generate_series
- SubPlan 1
- -> Index Only Scan using tenk1_unique1 on tenk1
- Index Cond: (unique1 = t.unique1)
+ SubPlan 1
+ -> Index Only Scan using tenk1_unique1 on tenk1
+ Index Cond: (unique1 = t.unique1)
(10 rows)
-- Parallel sort but with expression not available until the upper rel.
diff --git a/src/test/regress/expected/partition_prune.out b/src/test/regress/expected/partition_prune.out
index 9a4c48c055..c45590fdfe 100644
--- a/src/test/regress/expected/partition_prune.out
+++ b/src/test/regress/expected/partition_prune.out
@@ -1489,60 +1489,64 @@ EXPLAIN (VERBOSE, COSTS OFF) SELECT * FROM part p(x) ORDER BY x;
--
-- pruning won't work for mc3p, because some keys are Params
explain (costs off) select * from mc2p t1, lateral (select count(*) from mc3p t2 where t2.a = t1.b and abs(t2.b) = 1 and t2.c = 1) s where t1.a = 1;
- QUERY PLAN
------------------------------------------------------------------------
- Nested Loop
- -> Append
- -> Seq Scan on mc2p1 t1_1
- Filter: (a = 1)
- -> Seq Scan on mc2p2 t1_2
- Filter: (a = 1)
- -> Seq Scan on mc2p_default t1_3
- Filter: (a = 1)
- -> Aggregate
- -> Append
- -> Seq Scan on mc3p0 t2_1
- Filter: ((a = t1.b) AND (c = 1) AND (abs(b) = 1))
- -> Seq Scan on mc3p1 t2_2
- Filter: ((a = t1.b) AND (c = 1) AND (abs(b) = 1))
- -> Seq Scan on mc3p2 t2_3
- Filter: ((a = t1.b) AND (c = 1) AND (abs(b) = 1))
- -> Seq Scan on mc3p3 t2_4
- Filter: ((a = t1.b) AND (c = 1) AND (abs(b) = 1))
- -> Seq Scan on mc3p4 t2_5
- Filter: ((a = t1.b) AND (c = 1) AND (abs(b) = 1))
- -> Seq Scan on mc3p5 t2_6
- Filter: ((a = t1.b) AND (c = 1) AND (abs(b) = 1))
- -> Seq Scan on mc3p6 t2_7
- Filter: ((a = t1.b) AND (c = 1) AND (abs(b) = 1))
- -> Seq Scan on mc3p7 t2_8
- Filter: ((a = t1.b) AND (c = 1) AND (abs(b) = 1))
- -> Seq Scan on mc3p_default t2_9
- Filter: ((a = t1.b) AND (c = 1) AND (abs(b) = 1))
-(28 rows)
+ QUERY PLAN
+-----------------------------------------------------------------------------
+ Gather
+ Workers Planned: 2
+ -> Nested Loop
+ -> Parallel Append
+ -> Parallel Seq Scan on mc2p1 t1_1
+ Filter: (a = 1)
+ -> Parallel Seq Scan on mc2p2 t1_2
+ Filter: (a = 1)
+ -> Parallel Seq Scan on mc2p_default t1_3
+ Filter: (a = 1)
+ -> Aggregate
+ -> Append
+ -> Seq Scan on mc3p0 t2_1
+ Filter: ((a = t1.b) AND (c = 1) AND (abs(b) = 1))
+ -> Seq Scan on mc3p1 t2_2
+ Filter: ((a = t1.b) AND (c = 1) AND (abs(b) = 1))
+ -> Seq Scan on mc3p2 t2_3
+ Filter: ((a = t1.b) AND (c = 1) AND (abs(b) = 1))
+ -> Seq Scan on mc3p3 t2_4
+ Filter: ((a = t1.b) AND (c = 1) AND (abs(b) = 1))
+ -> Seq Scan on mc3p4 t2_5
+ Filter: ((a = t1.b) AND (c = 1) AND (abs(b) = 1))
+ -> Seq Scan on mc3p5 t2_6
+ Filter: ((a = t1.b) AND (c = 1) AND (abs(b) = 1))
+ -> Seq Scan on mc3p6 t2_7
+ Filter: ((a = t1.b) AND (c = 1) AND (abs(b) = 1))
+ -> Seq Scan on mc3p7 t2_8
+ Filter: ((a = t1.b) AND (c = 1) AND (abs(b) = 1))
+ -> Seq Scan on mc3p_default t2_9
+ Filter: ((a = t1.b) AND (c = 1) AND (abs(b) = 1))
+(30 rows)
-- pruning should work fine, because values for a prefix of keys (a, b) are
-- available
explain (costs off) select * from mc2p t1, lateral (select count(*) from mc3p t2 where t2.c = t1.b and abs(t2.b) = 1 and t2.a = 1) s where t1.a = 1;
- QUERY PLAN
------------------------------------------------------------------------
- Nested Loop
- -> Append
- -> Seq Scan on mc2p1 t1_1
- Filter: (a = 1)
- -> Seq Scan on mc2p2 t1_2
- Filter: (a = 1)
- -> Seq Scan on mc2p_default t1_3
- Filter: (a = 1)
- -> Aggregate
- -> Append
- -> Seq Scan on mc3p0 t2_1
- Filter: ((c = t1.b) AND (a = 1) AND (abs(b) = 1))
- -> Seq Scan on mc3p1 t2_2
- Filter: ((c = t1.b) AND (a = 1) AND (abs(b) = 1))
- -> Seq Scan on mc3p_default t2_3
- Filter: ((c = t1.b) AND (a = 1) AND (abs(b) = 1))
-(16 rows)
+ QUERY PLAN
+-----------------------------------------------------------------------------
+ Gather
+ Workers Planned: 2
+ -> Nested Loop
+ -> Parallel Append
+ -> Parallel Seq Scan on mc2p1 t1_1
+ Filter: (a = 1)
+ -> Parallel Seq Scan on mc2p2 t1_2
+ Filter: (a = 1)
+ -> Parallel Seq Scan on mc2p_default t1_3
+ Filter: (a = 1)
+ -> Aggregate
+ -> Append
+ -> Seq Scan on mc3p0 t2_1
+ Filter: ((c = t1.b) AND (a = 1) AND (abs(b) = 1))
+ -> Seq Scan on mc3p1 t2_2
+ Filter: ((c = t1.b) AND (a = 1) AND (abs(b) = 1))
+ -> Seq Scan on mc3p_default t2_3
+ Filter: ((c = t1.b) AND (a = 1) AND (abs(b) = 1))
+(18 rows)
-- also here, because values for all keys are provided
explain (costs off) select * from mc2p t1, lateral (select count(*) from mc3p t2 where t2.a = 1 and abs(t2.b) = 1 and t2.c = 1) s where t1.a = 1;
diff --git a/src/test/regress/expected/select_parallel.out b/src/test/regress/expected/select_parallel.out
index b76132ffe4..a6c4d6bf3f 100644
--- a/src/test/regress/expected/select_parallel.out
+++ b/src/test/regress/expected/select_parallel.out
@@ -130,30 +130,48 @@ select sp_test_func() order by 1;
foo
(2 rows)
--- Parallel Append is not to be used when the subpath depends on the outer param
+-- Parallel Append is can be used when the subpath depends on the outer params
+-- when those params are consumed within the worker that generates them.
create table part_pa_test(a int, b int) partition by range(a);
create table part_pa_test_p1 partition of part_pa_test for values from (minvalue) to (0);
create table part_pa_test_p2 partition of part_pa_test for values from (0) to (maxvalue);
-explain (costs off)
+explain (costs off, verbose)
select (select max((select pa1.b from part_pa_test pa1 where pa1.a = pa2.a)))
from part_pa_test pa2;
- QUERY PLAN
---------------------------------------------------------------
- Aggregate
+ QUERY PLAN
+---------------------------------------------------------------------------
+ Finalize Aggregate
+ Output: (SubPlan 2)
-> Gather
+ Output: (PARTIAL max((SubPlan 1)))
Workers Planned: 3
- -> Parallel Append
- -> Parallel Seq Scan on part_pa_test_p1 pa2_1
- -> Parallel Seq Scan on part_pa_test_p2 pa2_2
+ -> Partial Aggregate
+ Output: PARTIAL max((SubPlan 1))
+ -> Parallel Append
+ -> Parallel Seq Scan on public.part_pa_test_p1 pa2_1
+ Output: pa2_1.a
+ -> Parallel Seq Scan on public.part_pa_test_p2 pa2_2
+ Output: pa2_2.a
+ SubPlan 1
+ -> Append
+ -> Seq Scan on public.part_pa_test_p1 pa1_1
+ Output: pa1_1.b
+ Filter: (pa1_1.a = pa2.a)
+ -> Seq Scan on public.part_pa_test_p2 pa1_2
+ Output: pa1_2.b
+ Filter: (pa1_2.a = pa2.a)
SubPlan 2
-> Result
- SubPlan 1
- -> Append
- -> Seq Scan on part_pa_test_p1 pa1_1
- Filter: (a = pa2.a)
- -> Seq Scan on part_pa_test_p2 pa1_2
- Filter: (a = pa2.a)
-(14 rows)
+ Output: max((SubPlan 1))
+(23 rows)
+
+insert into part_pa_test(a, b) values (-1, 1), (1, 3);
+select (select max((select pa1.b from part_pa_test pa1 where pa1.a = pa2.a)))
+from part_pa_test pa2;
+ max
+-----
+ 3
+(1 row)
drop table part_pa_test;
-- test with leader participation disabled
@@ -320,19 +338,19 @@ explain (costs off, verbose) select
QUERY PLAN
----------------------------------------------------------------------------
Gather
- Output: (SubPlan 1)
+ Output: ((SubPlan 1))
Workers Planned: 4
-> Nested Loop
- Output: t.unique1
+ Output: (SubPlan 1)
-> Parallel Index Only Scan using tenk1_unique1 on public.tenk1 t
Output: t.unique1
-> Function Scan on pg_catalog.generate_series
Output: generate_series.generate_series
Function Call: generate_series(1, 10)
- SubPlan 1
- -> Index Only Scan using tenk1_unique1 on public.tenk1
- Output: t.unique1
- Index Cond: (tenk1.unique1 = t.unique1)
+ SubPlan 1
+ -> Index Only Scan using tenk1_unique1 on public.tenk1
+ Output: t.unique1
+ Index Cond: (tenk1.unique1 = t.unique1)
(14 rows)
explain (costs off, verbose) select
@@ -341,63 +359,69 @@ explain (costs off, verbose) select
QUERY PLAN
----------------------------------------------------------------------
Gather
- Output: (SubPlan 1)
+ Output: ((SubPlan 1))
Workers Planned: 4
-> Parallel Index Only Scan using tenk1_unique1 on public.tenk1 t
- Output: t.unique1
- SubPlan 1
- -> Index Only Scan using tenk1_unique1 on public.tenk1
- Output: t.unique1
- Index Cond: (tenk1.unique1 = t.unique1)
+ Output: (SubPlan 1)
+ SubPlan 1
+ -> Index Only Scan using tenk1_unique1 on public.tenk1
+ Output: t.unique1
+ Index Cond: (tenk1.unique1 = t.unique1)
(9 rows)
explain (costs off, verbose) select
(select t.unique1 from tenk1 where tenk1.unique1 = t.unique1)
from tenk1 t
limit 1;
- QUERY PLAN
--------------------------------------------------------------------
+ QUERY PLAN
+----------------------------------------------------------------------------
Limit
Output: ((SubPlan 1))
- -> Seq Scan on public.tenk1 t
- Output: (SubPlan 1)
- SubPlan 1
- -> Index Only Scan using tenk1_unique1 on public.tenk1
- Output: t.unique1
- Index Cond: (tenk1.unique1 = t.unique1)
-(8 rows)
+ -> Gather
+ Output: ((SubPlan 1))
+ Workers Planned: 4
+ -> Parallel Index Only Scan using tenk1_unique1 on public.tenk1 t
+ Output: (SubPlan 1)
+ SubPlan 1
+ -> Index Only Scan using tenk1_unique1 on public.tenk1
+ Output: t.unique1
+ Index Cond: (tenk1.unique1 = t.unique1)
+(11 rows)
explain (costs off, verbose) select t.unique1
from tenk1 t
where t.unique1 = (select t.unique1 from tenk1 where tenk1.unique1 = t.unique1);
- QUERY PLAN
--------------------------------------------------------------
- Seq Scan on public.tenk1 t
+ QUERY PLAN
+----------------------------------------------------------------------
+ Gather
Output: t.unique1
- Filter: (t.unique1 = (SubPlan 1))
- SubPlan 1
- -> Index Only Scan using tenk1_unique1 on public.tenk1
- Output: t.unique1
- Index Cond: (tenk1.unique1 = t.unique1)
-(7 rows)
+ Workers Planned: 4
+ -> Parallel Index Only Scan using tenk1_unique1 on public.tenk1 t
+ Output: t.unique1
+ Filter: (t.unique1 = (SubPlan 1))
+ SubPlan 1
+ -> Index Only Scan using tenk1_unique1 on public.tenk1
+ Output: t.unique1
+ Index Cond: (tenk1.unique1 = t.unique1)
+(10 rows)
explain (costs off, verbose) select *
from tenk1 t
order by (select t.unique1 from tenk1 where tenk1.unique1 = t.unique1);
- QUERY PLAN
-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
- Sort
+ QUERY PLAN
+----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
+ Gather Merge
Output: t.unique1, t.unique2, t.two, t.four, t.ten, t.twenty, t.hundred, t.thousand, t.twothousand, t.fivethous, t.tenthous, t.odd, t.even, t.stringu1, t.stringu2, t.string4, ((SubPlan 1))
- Sort Key: ((SubPlan 1))
- -> Gather
- Output: t.unique1, t.unique2, t.two, t.four, t.ten, t.twenty, t.hundred, t.thousand, t.twothousand, t.fivethous, t.tenthous, t.odd, t.even, t.stringu1, t.stringu2, t.string4, (SubPlan 1)
- Workers Planned: 4
+ Workers Planned: 4
+ -> Sort
+ Output: t.unique1, t.unique2, t.two, t.four, t.ten, t.twenty, t.hundred, t.thousand, t.twothousand, t.fivethous, t.tenthous, t.odd, t.even, t.stringu1, t.stringu2, t.string4, ((SubPlan 1))
+ Sort Key: ((SubPlan 1))
-> Parallel Seq Scan on public.tenk1 t
- Output: t.unique1, t.unique2, t.two, t.four, t.ten, t.twenty, t.hundred, t.thousand, t.twothousand, t.fivethous, t.tenthous, t.odd, t.even, t.stringu1, t.stringu2, t.string4
- SubPlan 1
- -> Index Only Scan using tenk1_unique1 on public.tenk1
- Output: t.unique1
- Index Cond: (tenk1.unique1 = t.unique1)
+ Output: t.unique1, t.unique2, t.two, t.four, t.ten, t.twenty, t.hundred, t.thousand, t.twothousand, t.fivethous, t.tenthous, t.odd, t.even, t.stringu1, t.stringu2, t.string4, (SubPlan 1)
+ SubPlan 1
+ -> Index Only Scan using tenk1_unique1 on public.tenk1
+ Output: t.unique1
+ Index Cond: (tenk1.unique1 = t.unique1)
(12 rows)
-- test subplan in join/lateral join
@@ -409,14 +433,14 @@ explain (costs off, verbose, timing off) select t.unique1, l.*
QUERY PLAN
----------------------------------------------------------------------
Gather
- Output: t.unique1, (SubPlan 1)
+ Output: t.unique1, ((SubPlan 1))
Workers Planned: 4
-> Parallel Index Only Scan using tenk1_unique1 on public.tenk1 t
- Output: t.unique1
- SubPlan 1
- -> Index Only Scan using tenk1_unique1 on public.tenk1
- Output: t.unique1
- Index Cond: (tenk1.unique1 = t.unique1)
+ Output: t.unique1, (SubPlan 1)
+ SubPlan 1
+ -> Index Only Scan using tenk1_unique1 on public.tenk1
+ Output: t.unique1
+ Index Cond: (tenk1.unique1 = t.unique1)
(9 rows)
-- can't put a gather at the top of a subplan that takes a param
@@ -1350,9 +1374,12 @@ SELECT 1 FROM tenk1_vw_sec
Workers Planned: 4
-> Parallel Index Only Scan using tenk1_unique1 on tenk1
SubPlan 1
- -> Aggregate
- -> Seq Scan on int4_tbl
- Filter: (f1 < tenk1_vw_sec.unique1)
-(9 rows)
+ -> Finalize Aggregate
+ -> Gather
+ Workers Planned: 1
+ -> Partial Aggregate
+ -> Parallel Seq Scan on int4_tbl
+ Filter: (f1 < tenk1_vw_sec.unique1)
+(12 rows)
rollback;
diff --git a/src/test/regress/sql/select_parallel.sql b/src/test/regress/sql/select_parallel.sql
index cc752a7d45..3fc24b2b94 100644
--- a/src/test/regress/sql/select_parallel.sql
+++ b/src/test/regress/sql/select_parallel.sql
@@ -53,13 +53,17 @@ $$ select 'foo'::varchar union all select 'bar'::varchar $$
language sql stable;
select sp_test_func() order by 1;
--- Parallel Append is not to be used when the subpath depends on the outer param
+-- Parallel Append is can be used when the subpath depends on the outer params
+-- when those params are consumed within the worker that generates them.
create table part_pa_test(a int, b int) partition by range(a);
create table part_pa_test_p1 partition of part_pa_test for values from (minvalue) to (0);
create table part_pa_test_p2 partition of part_pa_test for values from (0) to (maxvalue);
-explain (costs off)
+explain (costs off, verbose)
select (select max((select pa1.b from part_pa_test pa1 where pa1.a = pa2.a)))
from part_pa_test pa2;
+insert into part_pa_test(a, b) values (-1, 1), (1, 3);
+select (select max((select pa1.b from part_pa_test pa1 where pa1.a = pa2.a)))
+from part_pa_test pa2;
drop table part_pa_test;
-- test with leader participation disabled
--
2.39.3 (Apple Git-145)
[application/octet-stream] v12-0001-Add-tests-before-change.patch (9.3K, ../../CAAaqYe-Ld1q_b9pOf0PRjfQLWCgdkTvnopfeXgmrSvEQu0Ox=A@mail.gmail.com/3-v12-0001-Add-tests-before-change.patch)
download | inline diff:
From 3ba7b7b5a638cd74b5b8d546722514409d9e3fd3 Mon Sep 17 00:00:00 2001
From: jcoleman <[email protected]>
Date: Mon, 26 Sep 2022 20:30:23 -0400
Subject: [PATCH v12 1/2] Add tests before change
---
src/test/regress/expected/select_parallel.out | 137 ++++++++++++++++++
src/test/regress/sql/select_parallel.sql | 33 +++++
2 files changed, 170 insertions(+)
diff --git a/src/test/regress/expected/select_parallel.out b/src/test/regress/expected/select_parallel.out
index d88353d496..b76132ffe4 100644
--- a/src/test/regress/expected/select_parallel.out
+++ b/src/test/regress/expected/select_parallel.out
@@ -311,6 +311,143 @@ select count(*) from tenk1 where (two, four) not in
10000
(1 row)
+-- test parallel plans for queries containing correlated subplans
+-- where the subplan only needs params available from the current
+-- worker's scan.
+explain (costs off, verbose) select
+ (select t.unique1 from tenk1 where tenk1.unique1 = t.unique1)
+ from tenk1 t, generate_series(1, 10);
+ QUERY PLAN
+----------------------------------------------------------------------------
+ Gather
+ Output: (SubPlan 1)
+ Workers Planned: 4
+ -> Nested Loop
+ Output: t.unique1
+ -> Parallel Index Only Scan using tenk1_unique1 on public.tenk1 t
+ Output: t.unique1
+ -> Function Scan on pg_catalog.generate_series
+ Output: generate_series.generate_series
+ Function Call: generate_series(1, 10)
+ SubPlan 1
+ -> Index Only Scan using tenk1_unique1 on public.tenk1
+ Output: t.unique1
+ Index Cond: (tenk1.unique1 = t.unique1)
+(14 rows)
+
+explain (costs off, verbose) select
+ (select t.unique1 from tenk1 where tenk1.unique1 = t.unique1)
+ from tenk1 t;
+ QUERY PLAN
+----------------------------------------------------------------------
+ Gather
+ Output: (SubPlan 1)
+ Workers Planned: 4
+ -> Parallel Index Only Scan using tenk1_unique1 on public.tenk1 t
+ Output: t.unique1
+ SubPlan 1
+ -> Index Only Scan using tenk1_unique1 on public.tenk1
+ Output: t.unique1
+ Index Cond: (tenk1.unique1 = t.unique1)
+(9 rows)
+
+explain (costs off, verbose) select
+ (select t.unique1 from tenk1 where tenk1.unique1 = t.unique1)
+ from tenk1 t
+ limit 1;
+ QUERY PLAN
+-------------------------------------------------------------------
+ Limit
+ Output: ((SubPlan 1))
+ -> Seq Scan on public.tenk1 t
+ Output: (SubPlan 1)
+ SubPlan 1
+ -> Index Only Scan using tenk1_unique1 on public.tenk1
+ Output: t.unique1
+ Index Cond: (tenk1.unique1 = t.unique1)
+(8 rows)
+
+explain (costs off, verbose) select t.unique1
+ from tenk1 t
+ where t.unique1 = (select t.unique1 from tenk1 where tenk1.unique1 = t.unique1);
+ QUERY PLAN
+-------------------------------------------------------------
+ Seq Scan on public.tenk1 t
+ Output: t.unique1
+ Filter: (t.unique1 = (SubPlan 1))
+ SubPlan 1
+ -> Index Only Scan using tenk1_unique1 on public.tenk1
+ Output: t.unique1
+ Index Cond: (tenk1.unique1 = t.unique1)
+(7 rows)
+
+explain (costs off, verbose) select *
+ from tenk1 t
+ order by (select t.unique1 from tenk1 where tenk1.unique1 = t.unique1);
+ QUERY PLAN
+----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
+ Sort
+ Output: t.unique1, t.unique2, t.two, t.four, t.ten, t.twenty, t.hundred, t.thousand, t.twothousand, t.fivethous, t.tenthous, t.odd, t.even, t.stringu1, t.stringu2, t.string4, ((SubPlan 1))
+ Sort Key: ((SubPlan 1))
+ -> Gather
+ Output: t.unique1, t.unique2, t.two, t.four, t.ten, t.twenty, t.hundred, t.thousand, t.twothousand, t.fivethous, t.tenthous, t.odd, t.even, t.stringu1, t.stringu2, t.string4, (SubPlan 1)
+ Workers Planned: 4
+ -> Parallel Seq Scan on public.tenk1 t
+ Output: t.unique1, t.unique2, t.two, t.four, t.ten, t.twenty, t.hundred, t.thousand, t.twothousand, t.fivethous, t.tenthous, t.odd, t.even, t.stringu1, t.stringu2, t.string4
+ SubPlan 1
+ -> Index Only Scan using tenk1_unique1 on public.tenk1
+ Output: t.unique1
+ Index Cond: (tenk1.unique1 = t.unique1)
+(12 rows)
+
+-- test subplan in join/lateral join
+explain (costs off, verbose, timing off) select t.unique1, l.*
+ from tenk1 t
+ join lateral (
+ select (select t.unique1 from tenk1 where tenk1.unique1 = t.unique1 offset 0)
+ ) l on true;
+ QUERY PLAN
+----------------------------------------------------------------------
+ Gather
+ Output: t.unique1, (SubPlan 1)
+ Workers Planned: 4
+ -> Parallel Index Only Scan using tenk1_unique1 on public.tenk1 t
+ Output: t.unique1
+ SubPlan 1
+ -> Index Only Scan using tenk1_unique1 on public.tenk1
+ Output: t.unique1
+ Index Cond: (tenk1.unique1 = t.unique1)
+(9 rows)
+
+-- can't put a gather at the top of a subplan that takes a param
+-- (use a join in the subplan for the harder case)
+explain (costs off, verbose) select * from tenk1 t where t.two in (
+ select t.two
+ from tenk1
+ join tenk1 t3 on t3.stringu1 = tenk1.stringu1
+ where tenk1.four = t.four
+);
+ QUERY PLAN
+---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
+ Seq Scan on public.tenk1 t
+ Output: t.unique1, t.unique2, t.two, t.four, t.ten, t.twenty, t.hundred, t.thousand, t.twothousand, t.fivethous, t.tenthous, t.odd, t.even, t.stringu1, t.stringu2, t.string4
+ Filter: (SubPlan 1)
+ SubPlan 1
+ -> Hash Join
+ Output: t.two
+ Hash Cond: (tenk1.stringu1 = t3.stringu1)
+ -> Seq Scan on public.tenk1
+ Output: tenk1.unique1, tenk1.unique2, tenk1.two, tenk1.four, tenk1.ten, tenk1.twenty, tenk1.hundred, tenk1.thousand, tenk1.twothousand, tenk1.fivethous, tenk1.tenthous, tenk1.odd, tenk1.even, tenk1.stringu1, tenk1.stringu2, tenk1.string4
+ Filter: (tenk1.four = t.four)
+ -> Hash
+ Output: t3.stringu1
+ -> Gather
+ Output: t3.stringu1
+ Workers Planned: 4
+ -> Parallel Seq Scan on public.tenk1 t3
+ Output: t3.stringu1
+(17 rows)
+
-- this is not parallel-safe due to use of random() within SubLink's testexpr:
explain (costs off)
select * from tenk1 where (unique1 + random())::integer not in
diff --git a/src/test/regress/sql/select_parallel.sql b/src/test/regress/sql/select_parallel.sql
index 80c914dc02..cc752a7d45 100644
--- a/src/test/regress/sql/select_parallel.sql
+++ b/src/test/regress/sql/select_parallel.sql
@@ -111,6 +111,39 @@ explain (costs off)
(select hundred, thousand from tenk2 where thousand > 100);
select count(*) from tenk1 where (two, four) not in
(select hundred, thousand from tenk2 where thousand > 100);
+-- test parallel plans for queries containing correlated subplans
+-- where the subplan only needs params available from the current
+-- worker's scan.
+explain (costs off, verbose) select
+ (select t.unique1 from tenk1 where tenk1.unique1 = t.unique1)
+ from tenk1 t, generate_series(1, 10);
+explain (costs off, verbose) select
+ (select t.unique1 from tenk1 where tenk1.unique1 = t.unique1)
+ from tenk1 t;
+explain (costs off, verbose) select
+ (select t.unique1 from tenk1 where tenk1.unique1 = t.unique1)
+ from tenk1 t
+ limit 1;
+explain (costs off, verbose) select t.unique1
+ from tenk1 t
+ where t.unique1 = (select t.unique1 from tenk1 where tenk1.unique1 = t.unique1);
+explain (costs off, verbose) select *
+ from tenk1 t
+ order by (select t.unique1 from tenk1 where tenk1.unique1 = t.unique1);
+-- test subplan in join/lateral join
+explain (costs off, verbose, timing off) select t.unique1, l.*
+ from tenk1 t
+ join lateral (
+ select (select t.unique1 from tenk1 where tenk1.unique1 = t.unique1 offset 0)
+ ) l on true;
+-- can't put a gather at the top of a subplan that takes a param
+-- (use a join in the subplan for the harder case)
+explain (costs off, verbose) select * from tenk1 t where t.two in (
+ select t.two
+ from tenk1
+ join tenk1 t3 on t3.stringu1 = tenk1.stringu1
+ where tenk1.four = t.four
+);
-- this is not parallel-safe due to use of random() within SubLink's testexpr:
explain (costs off)
select * from tenk1 where (unique1 + random())::integer not in
--
2.39.3 (Apple Git-145)
^ permalink raw reply [nested|flat] 35+ messages in thread
* Re: Parallelize correlated subqueries that execute within each worker
@ 2024-01-31 02:56 James Coleman <[email protected]>
parent: Robert Haas <[email protected]>
0 siblings, 1 reply; 35+ messages in thread
From: James Coleman @ 2024-01-31 02:56 UTC (permalink / raw)
To: Robert Haas <[email protected]>; +Cc: Akshat Jaimini <[email protected]>; [email protected]
On Tue, Jan 30, 2024 at 11:54 AM Robert Haas <[email protected]> wrote:
>
> On Tue, Jan 30, 2024 at 11:17 AM Akshat Jaimini <[email protected]> wrote:
> > I think we should move this patch to the next CF as I believe that work is still going on resolving the last reported bug.
>
> We shouldn't just keep pushing this forward to the next CF. It's been
> idle since July. If it needs more work, mark it RwF and it can be
> reopened when there's something for a reviewer to do.
I don't follow the "Idle since July" since it just hasn't received
review since then, so there's been nothing to reply to.
That being said, Vignesh's note in January about a now-failing test is
relevant activity, and I've just today responded to that, so I'm
changing the status back from Waiting on Author to Needs Review.
Regards,
James Coleman
^ permalink raw reply [nested|flat] 35+ messages in thread
* Re: Parallelize correlated subqueries that execute within each worker
@ 2024-01-31 03:34 Tom Lane <[email protected]>
parent: James Coleman <[email protected]>
0 siblings, 1 reply; 35+ messages in thread
From: Tom Lane @ 2024-01-31 03:34 UTC (permalink / raw)
To: James Coleman <[email protected]>; +Cc: vignesh C <[email protected]>; Richard Guo <[email protected]>; Tomas Vondra <[email protected]>; Andres Freund <[email protected]>; Robert Haas <[email protected]>; pgsql-hackers; Amit Kapila <[email protected]>
James Coleman <[email protected]> writes:
> I've finally had a chance to look at this, and I don't believe there's
> any real failure here, merely drift of how the planner works on master
> resulting in this query now being eligible for a different plan shape.
> I was a bit wary at first because the changing test query is one I'd
> previously referenced in [1] as likely exposing the bug I'd fixed
> where params where being used across worker boundaries. However
> looking at the diff in the patch at that point (v10) that particular
> test query formed a different plan shape (there were two gather nodes
> being created, and params crossing between them).
> But in the current revision of master with the current patch applied
> that's no longer true: we have a Gather node, and the Subplan using
> the param is properly under that Gather node, and the param should be
> being both generated and consumed within the same worker process.
Hmm ... so the question this raises for me is: was that test intended
to verify behavior of params being passed across workers? If so,
haven't you broken the point of the test? This doesn't mean that
your code change is wrong; but I think maybe you need to find a way
to modify that test case so that it still tests what it's meant to.
This is a common hazard when changing the planner's behavior.
regards, tom lane
^ permalink raw reply [nested|flat] 35+ messages in thread
* Re: Parallelize correlated subqueries that execute within each worker
@ 2024-01-31 13:53 James Coleman <[email protected]>
parent: Tom Lane <[email protected]>
0 siblings, 0 replies; 35+ messages in thread
From: James Coleman @ 2024-01-31 13:53 UTC (permalink / raw)
To: Tom Lane <[email protected]>; +Cc: vignesh C <[email protected]>; Richard Guo <[email protected]>; Tomas Vondra <[email protected]>; Andres Freund <[email protected]>; Robert Haas <[email protected]>; pgsql-hackers; Amit Kapila <[email protected]>
On Tue, Jan 30, 2024 at 10:34 PM Tom Lane <[email protected]> wrote:
>
> James Coleman <[email protected]> writes:
> > I've finally had a chance to look at this, and I don't believe there's
> > any real failure here, merely drift of how the planner works on master
> > resulting in this query now being eligible for a different plan shape.
>
> > I was a bit wary at first because the changing test query is one I'd
> > previously referenced in [1] as likely exposing the bug I'd fixed
> > where params where being used across worker boundaries. However
> > looking at the diff in the patch at that point (v10) that particular
> > test query formed a different plan shape (there were two gather nodes
> > being created, and params crossing between them).
>
> > But in the current revision of master with the current patch applied
> > that's no longer true: we have a Gather node, and the Subplan using
> > the param is properly under that Gather node, and the param should be
> > being both generated and consumed within the same worker process.
>
> Hmm ... so the question this raises for me is: was that test intended
> to verify behavior of params being passed across workers? If so,
> haven't you broken the point of the test? This doesn't mean that
> your code change is wrong; but I think maybe you need to find a way
> to modify that test case so that it still tests what it's meant to.
> This is a common hazard when changing the planner's behavior.
I'd been thinking it was covered by another test I'd added in 0001,
but looking at it again that test doesn't exercise parallel append
(though it does exercise a different case of cross-worker param
usage), so I'll add another test for the parallel append behavior.
Regards,
James Coleman
^ permalink raw reply [nested|flat] 35+ messages in thread
* Re: Parallelize correlated subqueries that execute within each worker
@ 2024-01-31 20:18 Robert Haas <[email protected]>
parent: James Coleman <[email protected]>
0 siblings, 0 replies; 35+ messages in thread
From: Robert Haas @ 2024-01-31 20:18 UTC (permalink / raw)
To: James Coleman <[email protected]>; +Cc: Akshat Jaimini <[email protected]>; [email protected]
On Tue, Jan 30, 2024 at 9:56 PM James Coleman <[email protected]> wrote:
> I don't follow the "Idle since July" since it just hasn't received
> review since then, so there's been nothing to reply to.
It wasn't clear to me if you thought that the patch was ready for
review since July, or if it was waiting on you since July. Those are
quite different, IMV.
> That being said, Vignesh's note in January about a now-failing test is
> relevant activity, and I've just today responded to that, so I'm
> changing the status back from Waiting on Author to Needs Review.
Sounds good.
--
Robert Haas
EDB: http://www.enterprisedb.com
^ permalink raw reply [nested|flat] 35+ messages in thread
* Re: Parallelize correlated subqueries that execute within each worker
@ 2025-07-03 14:04 Andy Fan <[email protected]>
parent: James Coleman <[email protected]>
1 sibling, 0 replies; 35+ messages in thread
From: Andy Fan @ 2025-07-03 14:04 UTC (permalink / raw)
To: James Coleman <[email protected]>; +Cc: Tomas Vondra <[email protected]>; vignesh C <[email protected]>; Andres Freund <[email protected]>; Robert Haas <[email protected]>; pgsql-hackers; Amit Kapila <[email protected]>; Tom Lane <[email protected]>
Hi James:
Very nice to find this topic, I am recently working on this topic [1] as
well without finding this topic has been discussed before. I just go
through this thread and find it goes with a different direction with mine.
would you mind to check my soluation to see is there any case I can't
cover? I suggested this because my soluation should be much easier than
yours. But I'm not suprised to know I'm miss some obvious keypoint.
>
>> One of the queries in in incremental_sort changed plans a little bit:
>>
>> explain (costs off) select distinct
>> unique1,
>> (select t.unique1 from tenk1 where tenk1.unique1 = t.unique1)
>> from tenk1 t, generate_series(1, 1000);
>>
>> switched from
>>
>> Unique (cost=18582710.41..18747375.21 rows=10000 width=8)
>> -> Gather Merge (cost=18582710.41..18697375.21 rows=10000000 ...)
>> Workers Planned: 2
>> -> Sort (cost=18582710.39..18593127.06 rows=4166667 ...)
>> Sort Key: t.unique1, ((SubPlan 1))
>> ...
>>
>> to
>>
>> Unique (cost=18582710.41..18614268.91 rows=10000 ...)
>> -> Gather Merge (cost=18582710.41..18614168.91 rows=20000 ...)
>> Workers Planned: 2
>> -> Unique (cost=18582710.39..18613960.39 rows=10000 ...)
>> -> Sort (cost=18582710.39..18593127.06 ...)
>> Sort Key: t.unique1, ((SubPlan 1))
>> ...
>>
>> which probably makes sense, as the cost estimate decreases a bit.
>
> Off the cuff that seems fine. I'll read it over again when I send the
> updated series.
I had a detailed explaination for this plan change in [1] and I think
this could be amazing gain no matter which way we go finally.
[1] https://www.postgresql.org/message-id/[email protected]
--
Best Regards
Andy Fan
^ permalink raw reply [nested|flat] 35+ messages in thread
end of thread, other threads:[~2025-07-03 14:04 UTC | newest]
Thread overview: 35+ messages (download: mbox mbox.gz follow: Atom feed)
-- links below jump to the message on this page --
2021-05-07 16:30 Parallelize correlated subqueries that execute within each worker James Coleman <[email protected]>
2021-09-01 11:06 ` Daniel Gustafsson <[email protected]>
2021-09-07 13:16 ` James Coleman <[email protected]>
2021-09-07 15:06 ` Zhihong Yu <[email protected]>
2021-09-08 12:47 ` James Coleman <[email protected]>
2021-11-03 13:46 ` James Coleman <[email protected]>
2021-11-03 14:48 ` Robert Haas <[email protected]>
2021-11-03 15:14 ` Tom Lane <[email protected]>
2021-11-03 16:27 ` Robert Haas <[email protected]>
2021-11-03 16:52 ` Tom Lane <[email protected]>
2021-11-03 17:34 ` James Coleman <[email protected]>
2021-11-15 15:01 ` Robert Haas <[email protected]>
2021-12-03 07:35 ` Michael Paquier <[email protected]>
2022-08-02 20:57 ` Jacob Champion <[email protected]>
2022-09-27 02:56 ` James Coleman <[email protected]>
2023-01-23 14:00 ` James Coleman <[email protected]>
2023-02-06 16:40 ` Antonin Houska <[email protected]>
2023-02-08 13:38 ` James Coleman <[email protected]>
2023-03-08 18:07 ` Antonin Houska <[email protected]>
2023-06-06 09:35 ` Richard Guo <[email protected]>
2023-06-12 02:23 ` James Coleman <[email protected]>
2023-06-26 06:47 ` Richard Guo <[email protected]>
2023-07-04 01:26 ` James Coleman <[email protected]>
2024-01-09 07:08 ` vignesh C <[email protected]>
2024-01-23 14:33 ` Akshat Jaimini <[email protected]>
2024-01-23 20:20 ` Robert Haas <[email protected]>
2024-01-30 16:16 ` Akshat Jaimini <[email protected]>
2024-01-30 16:54 ` Robert Haas <[email protected]>
2024-01-31 02:56 ` James Coleman <[email protected]>
2024-01-31 20:18 ` Robert Haas <[email protected]>
2024-01-31 02:51 ` James Coleman <[email protected]>
2024-01-31 03:34 ` Tom Lane <[email protected]>
2024-01-31 13:53 ` James Coleman <[email protected]>
2025-07-03 14:04 ` Andy Fan <[email protected]>
2023-02-24 20:07 [PATCH 1/4] f!fixes for LZ4 Justin Pryzby <[email protected]>
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