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* [PATCH v18 2/2] New command ALTER TABLE ALL IN TABLESPACE SET LOGGED/UNLOGGED
@ 2020-11-11 14:21 Kyotaro Horiguchi <[email protected]>
0 siblings, 0 replies; 2+ messages in thread
From: Kyotaro Horiguchi @ 2020-11-11 14:21 UTC (permalink / raw)
To ease invoking ALTER TABLE SET LOGGED/UNLOGGED, this command changes
relation persistence of all tables in the specified tablespace.
---
doc/src/sgml/ref/alter_table.sgml | 15 +++
src/backend/commands/tablecmds.c | 140 +++++++++++++++++++++++
src/backend/nodes/copyfuncs.c | 16 +++
src/backend/nodes/equalfuncs.c | 15 +++
src/backend/parser/gram.y | 42 +++++++
src/backend/tcop/utility.c | 11 ++
src/include/commands/tablecmds.h | 2 +
src/include/nodes/nodes.h | 1 +
src/include/nodes/parsenodes.h | 10 ++
src/test/regress/expected/tablespace.out | 76 ++++++++++++
src/test/regress/sql/tablespace.sql | 41 +++++++
11 files changed, 369 insertions(+)
diff --git a/doc/src/sgml/ref/alter_table.sgml b/doc/src/sgml/ref/alter_table.sgml
index 5c0735e08a..b03d5511a6 100644
--- a/doc/src/sgml/ref/alter_table.sgml
+++ b/doc/src/sgml/ref/alter_table.sgml
@@ -33,6 +33,8 @@ ALTER TABLE [ IF EXISTS ] <replaceable class="parameter">name</replaceable>
SET SCHEMA <replaceable class="parameter">new_schema</replaceable>
ALTER TABLE ALL IN TABLESPACE <replaceable class="parameter">name</replaceable> [ OWNED BY <replaceable class="parameter">role_name</replaceable> [, ... ] ]
SET TABLESPACE <replaceable class="parameter">new_tablespace</replaceable> [ NOWAIT ]
+ALTER TABLE ALL IN TABLESPACE <replaceable class="parameter">name</replaceable> [ OWNED BY <replaceable class="parameter">role_name</replaceable> [, ... ] ]
+ SET { LOGGED | UNLOGGED } [ NOWAIT ]
ALTER TABLE [ IF EXISTS ] <replaceable class="parameter">name</replaceable>
ATTACH PARTITION <replaceable class="parameter">partition_name</replaceable> { FOR VALUES <replaceable class="parameter">partition_bound_spec</replaceable> | DEFAULT }
ALTER TABLE [ IF EXISTS ] <replaceable class="parameter">name</replaceable>
@@ -753,6 +755,19 @@ WITH ( MODULUS <replaceable class="parameter">numeric_literal</replaceable>, REM
(see <xref linkend="sql-createtable-unlogged"/>). It cannot be applied
to a temporary table.
</para>
+
+ <para>
+ All tables in the current database in a tablespace can be changed by using
+ the <literal>ALL IN TABLESPACE</literal> form, which will lock all tables
+ to be changed first and then change each one. This form also supports
+ <literal>OWNED BY</literal>, which will only change tables owned by the
+ roles specified. If the <literal>NOWAIT</literal> option is specified
+ then the command will fail if it is unable to acquire all of the locks
+ required immediately. The <literal>information_schema</literal>
+ relations are not considered part of the system catalogs and will be
+ changed. See also
+ <link linkend="sql-createtablespace"><command>CREATE TABLESPACE</command></link>.
+ </para>
</listitem>
</varlistentry>
diff --git a/src/backend/commands/tablecmds.c b/src/backend/commands/tablecmds.c
index 9e5b77e94a..0724d0e1d2 100644
--- a/src/backend/commands/tablecmds.c
+++ b/src/backend/commands/tablecmds.c
@@ -14770,6 +14770,146 @@ AlterTableMoveAll(AlterTableMoveAllStmt *stmt)
return new_tablespaceoid;
}
+/*
+ * Alter Table ALL ... SET LOGGED/UNLOGGED
+ *
+ * Allows a user to change persistence of all objects in a given tablespace in
+ * the current database. Objects can be chosen based on the owner of the
+ * object also, to allow users to change persistene only their objects. The
+ * main permissions handling is done by the lower-level change persistence
+ * function.
+ *
+ * All to-be-modified objects are locked first. If NOWAIT is specified and the
+ * lock can't be acquired then we ereport(ERROR).
+ */
+void
+AlterTableSetLoggedAll(AlterTableSetLoggedAllStmt *stmt)
+{
+ List *relations = NIL;
+ ListCell *l;
+ ScanKeyData key[1];
+ Relation rel;
+ TableScanDesc scan;
+ HeapTuple tuple;
+ Oid tablespaceoid;
+ List *role_oids = roleSpecsToIds(stmt->roles);
+
+ /* Ensure we were not asked to change something we can't */
+ if (stmt->objtype != OBJECT_TABLE)
+ ereport(ERROR,
+ (errcode(ERRCODE_INVALID_PARAMETER_VALUE),
+ errmsg("only tables can be specified")));
+
+ /* Get the tablespace OID */
+ tablespaceoid = get_tablespace_oid(stmt->tablespacename, false);
+
+ /*
+ * Now that the checks are done, check if we should set either to
+ * InvalidOid because it is our database's default tablespace.
+ */
+ if (tablespaceoid == MyDatabaseTableSpace)
+ tablespaceoid = InvalidOid;
+
+ /*
+ * Walk the list of objects in the tablespace to pick up them. This will
+ * only find objects in our database, of course.
+ */
+ ScanKeyInit(&key[0],
+ Anum_pg_class_reltablespace,
+ BTEqualStrategyNumber, F_OIDEQ,
+ ObjectIdGetDatum(tablespaceoid));
+
+ rel = table_open(RelationRelationId, AccessShareLock);
+ scan = table_beginscan_catalog(rel, 1, key);
+ while ((tuple = heap_getnext(scan, ForwardScanDirection)) != NULL)
+ {
+ Form_pg_class relForm = (Form_pg_class) GETSTRUCT(tuple);
+ Oid relOid = relForm->oid;
+
+ /*
+ * Do not pick-up objects in pg_catalog as part of this, if an admin
+ * really wishes to do so, they can issue the individual ALTER
+ * commands directly.
+ *
+ * Also, explicitly avoid any shared tables, temp tables, or TOAST
+ * (TOAST will be changed with the main table).
+ */
+ if (IsCatalogNamespace(relForm->relnamespace) ||
+ relForm->relisshared ||
+ isAnyTempNamespace(relForm->relnamespace) ||
+ IsToastNamespace(relForm->relnamespace))
+ continue;
+
+ /* Only pick up the object type requested */
+ if (relForm->relkind != RELKIND_RELATION)
+ continue;
+
+ /* Check if we are only picking-up objects owned by certain roles */
+ if (role_oids != NIL && !list_member_oid(role_oids, relForm->relowner))
+ continue;
+
+ /*
+ * Handle permissions-checking here since we are locking the tables
+ * and also to avoid doing a bunch of work only to fail part-way. Note
+ * that permissions will also be checked by AlterTableInternal().
+ *
+ * Caller must be considered an owner on the table of which we're going
+ * to change persistence.
+ */
+ if (!pg_class_ownercheck(relOid, GetUserId()))
+ aclcheck_error(ACLCHECK_NOT_OWNER, get_relkind_objtype(get_rel_relkind(relOid)),
+ NameStr(relForm->relname));
+
+ if (stmt->nowait &&
+ !ConditionalLockRelationOid(relOid, AccessExclusiveLock))
+ ereport(ERROR,
+ (errcode(ERRCODE_OBJECT_IN_USE),
+ errmsg("aborting because lock on relation \"%s.%s\" is not available",
+ get_namespace_name(relForm->relnamespace),
+ NameStr(relForm->relname))));
+ else
+ LockRelationOid(relOid, AccessExclusiveLock);
+
+ /*
+ * Add to our list of objects of which we're going to change
+ * persistence.
+ */
+ relations = lappend_oid(relations, relOid);
+ }
+
+ table_endscan(scan);
+ table_close(rel, AccessShareLock);
+
+ if (relations == NIL)
+ ereport(NOTICE,
+ (errcode(ERRCODE_NO_DATA_FOUND),
+ errmsg("no matching relations in tablespace \"%s\" found",
+ tablespaceoid == InvalidOid ? "(database default)" :
+ get_tablespace_name(tablespaceoid))));
+
+ /*
+ * Everything is locked, loop through and change persistence of all of the
+ * relations.
+ */
+ foreach(l, relations)
+ {
+ List *cmds = NIL;
+ AlterTableCmd *cmd = makeNode(AlterTableCmd);
+
+ if (stmt->logged)
+ cmd->subtype = AT_SetLogged;
+ else
+ cmd->subtype = AT_SetUnLogged;
+
+ cmds = lappend(cmds, cmd);
+
+ EventTriggerAlterTableStart((Node *) stmt);
+ /* OID is set by AlterTableInternal */
+ AlterTableInternal(lfirst_oid(l), cmds, false);
+ EventTriggerAlterTableEnd();
+ }
+}
+
static void
index_copy_data(Relation rel, RelFileNode newrnode)
{
diff --git a/src/backend/nodes/copyfuncs.c b/src/backend/nodes/copyfuncs.c
index d4f8455a2b..ba605405a9 100644
--- a/src/backend/nodes/copyfuncs.c
+++ b/src/backend/nodes/copyfuncs.c
@@ -4285,6 +4285,19 @@ _copyAlterTableMoveAllStmt(const AlterTableMoveAllStmt *from)
return newnode;
}
+static AlterTableSetLoggedAllStmt *
+_copyAlterTableSetLoggedAllStmt(const AlterTableSetLoggedAllStmt *from)
+{
+ AlterTableSetLoggedAllStmt *newnode = makeNode(AlterTableSetLoggedAllStmt);
+
+ COPY_STRING_FIELD(tablespacename);
+ COPY_SCALAR_FIELD(objtype);
+ COPY_SCALAR_FIELD(logged);
+ COPY_SCALAR_FIELD(nowait);
+
+ return newnode;
+}
+
static CreateExtensionStmt *
_copyCreateExtensionStmt(const CreateExtensionStmt *from)
{
@@ -5655,6 +5668,9 @@ copyObjectImpl(const void *from)
case T_AlterTableMoveAllStmt:
retval = _copyAlterTableMoveAllStmt(from);
break;
+ case T_AlterTableSetLoggedAllStmt:
+ retval = _copyAlterTableSetLoggedAllStmt(from);
+ break;
case T_CreateExtensionStmt:
retval = _copyCreateExtensionStmt(from);
break;
diff --git a/src/backend/nodes/equalfuncs.c b/src/backend/nodes/equalfuncs.c
index f1002afe7a..b76fc872a5 100644
--- a/src/backend/nodes/equalfuncs.c
+++ b/src/backend/nodes/equalfuncs.c
@@ -1925,6 +1925,18 @@ _equalAlterTableMoveAllStmt(const AlterTableMoveAllStmt *a,
return true;
}
+static bool
+_equalAlterTableSetLoggedAllStmt(const AlterTableSetLoggedAllStmt *a,
+ const AlterTableSetLoggedAllStmt *b)
+{
+ COMPARE_STRING_FIELD(tablespacename);
+ COMPARE_SCALAR_FIELD(objtype);
+ COMPARE_SCALAR_FIELD(logged);
+ COMPARE_SCALAR_FIELD(nowait);
+
+ return true;
+}
+
static bool
_equalCreateExtensionStmt(const CreateExtensionStmt *a, const CreateExtensionStmt *b)
{
@@ -3650,6 +3662,9 @@ equal(const void *a, const void *b)
case T_AlterTableMoveAllStmt:
retval = _equalAlterTableMoveAllStmt(a, b);
break;
+ case T_AlterTableSetLoggedAllStmt:
+ retval = _equalAlterTableSetLoggedAllStmt(a, b);
+ break;
case T_CreateExtensionStmt:
retval = _equalCreateExtensionStmt(a, b);
break;
diff --git a/src/backend/parser/gram.y b/src/backend/parser/gram.y
index a03b33b53b..f8a41de2dd 100644
--- a/src/backend/parser/gram.y
+++ b/src/backend/parser/gram.y
@@ -1985,6 +1985,48 @@ AlterTableStmt:
n->nowait = $13;
$$ = (Node *)n;
}
+ | ALTER TABLE ALL IN_P TABLESPACE name SET LOGGED opt_nowait
+ {
+ AlterTableSetLoggedAllStmt *n =
+ makeNode(AlterTableSetLoggedAllStmt);
+ n->tablespacename = $6;
+ n->objtype = OBJECT_TABLE;
+ n->logged = true;
+ n->nowait = $9;
+ $$ = (Node *)n;
+ }
+ | ALTER TABLE ALL IN_P TABLESPACE name OWNED BY role_list SET LOGGED opt_nowait
+ {
+ AlterTableSetLoggedAllStmt *n =
+ makeNode(AlterTableSetLoggedAllStmt);
+ n->tablespacename = $6;
+ n->objtype = OBJECT_TABLE;
+ n->roles = $9;
+ n->logged = true;
+ n->nowait = $12;
+ $$ = (Node *)n;
+ }
+ | ALTER TABLE ALL IN_P TABLESPACE name SET UNLOGGED opt_nowait
+ {
+ AlterTableSetLoggedAllStmt *n =
+ makeNode(AlterTableSetLoggedAllStmt);
+ n->tablespacename = $6;
+ n->objtype = OBJECT_TABLE;
+ n->logged = false;
+ n->nowait = $9;
+ $$ = (Node *)n;
+ }
+ | ALTER TABLE ALL IN_P TABLESPACE name OWNED BY role_list SET UNLOGGED opt_nowait
+ {
+ AlterTableSetLoggedAllStmt *n =
+ makeNode(AlterTableSetLoggedAllStmt);
+ n->tablespacename = $6;
+ n->objtype = OBJECT_TABLE;
+ n->roles = $9;
+ n->logged = false;
+ n->nowait = $12;
+ $$ = (Node *)n;
+ }
| ALTER INDEX qualified_name alter_table_cmds
{
AlterTableStmt *n = makeNode(AlterTableStmt);
diff --git a/src/backend/tcop/utility.c b/src/backend/tcop/utility.c
index 3780c6e812..80d1e360b3 100644
--- a/src/backend/tcop/utility.c
+++ b/src/backend/tcop/utility.c
@@ -163,6 +163,7 @@ ClassifyUtilityCommandAsReadOnly(Node *parsetree)
case T_AlterTSConfigurationStmt:
case T_AlterTSDictionaryStmt:
case T_AlterTableMoveAllStmt:
+ case T_AlterTableSetLoggedAllStmt:
case T_AlterTableSpaceOptionsStmt:
case T_AlterTableStmt:
case T_AlterTypeStmt:
@@ -1753,6 +1754,12 @@ ProcessUtilitySlow(ParseState *pstate,
commandCollected = true;
break;
+ case T_AlterTableSetLoggedAllStmt:
+ AlterTableSetLoggedAll((AlterTableSetLoggedAllStmt *) parsetree);
+ /* commands are stashed in AlterTableSetLoggedAll */
+ commandCollected = true;
+ break;
+
case T_DropStmt:
ExecDropStmt((DropStmt *) parsetree, isTopLevel);
/* no commands stashed for DROP */
@@ -2675,6 +2682,10 @@ CreateCommandTag(Node *parsetree)
tag = AlterObjectTypeCommandTag(((AlterTableMoveAllStmt *) parsetree)->objtype);
break;
+ case T_AlterTableSetLoggedAllStmt:
+ tag = AlterObjectTypeCommandTag(((AlterTableSetLoggedAllStmt *) parsetree)->objtype);
+ break;
+
case T_AlterTableStmt:
tag = AlterObjectTypeCommandTag(((AlterTableStmt *) parsetree)->objtype);
break;
diff --git a/src/include/commands/tablecmds.h b/src/include/commands/tablecmds.h
index 5d4037f26e..c381dad3e5 100644
--- a/src/include/commands/tablecmds.h
+++ b/src/include/commands/tablecmds.h
@@ -42,6 +42,8 @@ extern void AlterTableInternal(Oid relid, List *cmds, bool recurse);
extern Oid AlterTableMoveAll(AlterTableMoveAllStmt *stmt);
+extern void AlterTableSetLoggedAll(AlterTableSetLoggedAllStmt *stmt);
+
extern ObjectAddress AlterTableNamespace(AlterObjectSchemaStmt *stmt,
Oid *oldschema);
diff --git a/src/include/nodes/nodes.h b/src/include/nodes/nodes.h
index 5d075f0c34..d8e1f223c8 100644
--- a/src/include/nodes/nodes.h
+++ b/src/include/nodes/nodes.h
@@ -430,6 +430,7 @@ typedef enum NodeTag
T_AlterCollationStmt,
T_CallStmt,
T_AlterStatsStmt,
+ T_AlterTableSetLoggedAllStmt,
/*
* TAGS FOR PARSE TREE NODES (parsenodes.h)
diff --git a/src/include/nodes/parsenodes.h b/src/include/nodes/parsenodes.h
index 1617702d9d..4fa9d9360f 100644
--- a/src/include/nodes/parsenodes.h
+++ b/src/include/nodes/parsenodes.h
@@ -2352,6 +2352,16 @@ typedef struct AlterTableMoveAllStmt
bool nowait;
} AlterTableMoveAllStmt;
+typedef struct AlterTableSetLoggedAllStmt
+{
+ NodeTag type;
+ char *tablespacename;
+ ObjectType objtype; /* Object type to move */
+ List *roles; /* List of roles to change objects of */
+ bool logged;
+ bool nowait;
+} AlterTableSetLoggedAllStmt;
+
/* ----------------------
* Create/Alter Extension Statements
* ----------------------
diff --git a/src/test/regress/expected/tablespace.out b/src/test/regress/expected/tablespace.out
index 2dfbcfdebe..c02afdcb68 100644
--- a/src/test/regress/expected/tablespace.out
+++ b/src/test/regress/expected/tablespace.out
@@ -943,5 +943,81 @@ drop cascades to table testschema.asexecute
drop cascades to table testschema.part
drop cascades to table testschema.atable
drop cascades to table testschema.tablespace_acl
+--
+-- Check persistence change in a tablespace
+CREATE SCHEMA testschema;
+GRANT CREATE ON SCHEMA testschema TO regress_tablespace_user1;
+CREATE TABLESPACE regress_tablespace LOCATION '';
+GRANT CREATE ON TABLESPACE regress_tablespace TO regress_tablespace_user1;
+CREATE TABLE testschema.lsu(a int) TABLESPACE regress_tablespace;
+CREATE UNLOGGED TABLE testschema.usu(a int) TABLESPACE regress_tablespace;
+CREATE TABLE testschema._lsu(a int) TABLESPACE pg_default;
+CREATE UNLOGGED TABLE testschema._usu(a int) TABLESPACE pg_default;
+SET ROLE regress_tablespace_user1;
+CREATE TABLE testschema.lu1(a int) TABLESPACE regress_tablespace;
+CREATE UNLOGGED TABLE testschema.uu1(a int) TABLESPACE regress_tablespace;
+CREATE TABLE testschema._lu1(a int) TABLESPACE pg_default;
+CREATE UNLOGGED TABLE testschema._uu1(a int) TABLESPACE pg_default;
+SELECT relname, t.spcname, relpersistence
+ FROM pg_class c LEFT JOIN pg_tablespace t ON (c.reltablespace = t.oid)
+ WHERE relnamespace = 'testschema'::regnamespace ORDER BY spcname, c.oid;
+ relname | spcname | relpersistence
+---------+--------------------+----------------
+ lsu | regress_tablespace | p
+ usu | regress_tablespace | u
+ lu1 | regress_tablespace | p
+ uu1 | regress_tablespace | u
+ _lsu | | p
+ _usu | | u
+ _lu1 | | p
+ _uu1 | | u
+(8 rows)
+
+ALTER TABLE ALL IN TABLESPACE regress_tablespace
+ OWNED BY regress_tablespace_user1 SET LOGGED;
+SELECT relname, t.spcname, relpersistence
+ FROM pg_class c LEFT JOIN pg_tablespace t ON (c.reltablespace = t.oid)
+ WHERE relnamespace = 'testschema'::regnamespace ORDER BY spcname, c.oid;
+ relname | spcname | relpersistence
+---------+--------------------+----------------
+ lsu | regress_tablespace | p
+ usu | regress_tablespace | u
+ lu1 | regress_tablespace | p
+ uu1 | regress_tablespace | p
+ _lsu | | p
+ _usu | | u
+ _lu1 | | p
+ _uu1 | | u
+(8 rows)
+
+RESET ROLE;
+ALTER TABLE ALL IN TABLESPACE regress_tablespace SET UNLOGGED;
+SELECT relname, t.spcname, relpersistence
+ FROM pg_class c LEFT JOIN pg_tablespace t ON (c.reltablespace = t.oid)
+ WHERE relnamespace = 'testschema'::regnamespace ORDER BY spcname, c.oid;
+ relname | spcname | relpersistence
+---------+--------------------+----------------
+ lsu | regress_tablespace | u
+ usu | regress_tablespace | u
+ lu1 | regress_tablespace | u
+ uu1 | regress_tablespace | u
+ _lsu | | p
+ _usu | | u
+ _lu1 | | p
+ _uu1 | | u
+(8 rows)
+
+-- Should succeed
+DROP SCHEMA testschema CASCADE;
+NOTICE: drop cascades to 8 other objects
+DETAIL: drop cascades to table testschema.lsu
+drop cascades to table testschema.usu
+drop cascades to table testschema._lsu
+drop cascades to table testschema._usu
+drop cascades to table testschema.lu1
+drop cascades to table testschema.uu1
+drop cascades to table testschema._lu1
+drop cascades to table testschema._uu1
+DROP TABLESPACE regress_tablespace;
DROP ROLE regress_tablespace_user1;
DROP ROLE regress_tablespace_user2;
diff --git a/src/test/regress/sql/tablespace.sql b/src/test/regress/sql/tablespace.sql
index 896f05cea3..4e407eb8c0 100644
--- a/src/test/regress/sql/tablespace.sql
+++ b/src/test/regress/sql/tablespace.sql
@@ -419,5 +419,46 @@ DROP TABLESPACE regress_tblspace_renamed;
DROP SCHEMA testschema CASCADE;
+
+--
+-- Check persistence change in a tablespace
+CREATE SCHEMA testschema;
+GRANT CREATE ON SCHEMA testschema TO regress_tablespace_user1;
+CREATE TABLESPACE regress_tablespace LOCATION '';
+GRANT CREATE ON TABLESPACE regress_tablespace TO regress_tablespace_user1;
+
+CREATE TABLE testschema.lsu(a int) TABLESPACE regress_tablespace;
+CREATE UNLOGGED TABLE testschema.usu(a int) TABLESPACE regress_tablespace;
+CREATE TABLE testschema._lsu(a int) TABLESPACE pg_default;
+CREATE UNLOGGED TABLE testschema._usu(a int) TABLESPACE pg_default;
+SET ROLE regress_tablespace_user1;
+CREATE TABLE testschema.lu1(a int) TABLESPACE regress_tablespace;
+CREATE UNLOGGED TABLE testschema.uu1(a int) TABLESPACE regress_tablespace;
+CREATE TABLE testschema._lu1(a int) TABLESPACE pg_default;
+CREATE UNLOGGED TABLE testschema._uu1(a int) TABLESPACE pg_default;
+
+SELECT relname, t.spcname, relpersistence
+ FROM pg_class c LEFT JOIN pg_tablespace t ON (c.reltablespace = t.oid)
+ WHERE relnamespace = 'testschema'::regnamespace ORDER BY spcname, c.oid;
+
+ALTER TABLE ALL IN TABLESPACE regress_tablespace
+ OWNED BY regress_tablespace_user1 SET LOGGED;
+
+SELECT relname, t.spcname, relpersistence
+ FROM pg_class c LEFT JOIN pg_tablespace t ON (c.reltablespace = t.oid)
+ WHERE relnamespace = 'testschema'::regnamespace ORDER BY spcname, c.oid;
+
+RESET ROLE;
+
+ALTER TABLE ALL IN TABLESPACE regress_tablespace SET UNLOGGED;
+
+SELECT relname, t.spcname, relpersistence
+ FROM pg_class c LEFT JOIN pg_tablespace t ON (c.reltablespace = t.oid)
+ WHERE relnamespace = 'testschema'::regnamespace ORDER BY spcname, c.oid;
+
+-- Should succeed
+DROP SCHEMA testschema CASCADE;
+DROP TABLESPACE regress_tablespace;
+
DROP ROLE regress_tablespace_user1;
DROP ROLE regress_tablespace_user2;
--
2.27.0
----Next_Part(Tue_Mar__1_14_14_13_2022_434)----
^ permalink raw reply [nested|flat] 2+ messages in thread
* RE: Exit walsender before confirming remote flush in logical replication
@ 2023-01-27 04:11 Hayato Kuroda (Fujitsu) <[email protected]>
0 siblings, 0 replies; 2+ messages in thread
From: Hayato Kuroda (Fujitsu) @ 2023-01-27 04:11 UTC (permalink / raw)
To: 'Dilip Kumar' <[email protected]>; Amit Kapila <[email protected]>; +Cc: Andres Freund <[email protected]>; Michael Paquier <[email protected]>; Peter Eisentraut <[email protected]>; Kyotaro Horiguchi <[email protected]>; pgsql-hackers
Dear Dilip, hackers,
Thanks for giving your opinion. I analyzed the relation with the given commit,
and I thought I could keep my patch. How do you think?
# Abstract
* Some modifications should be needed.
* We cannot rollback the shutdown if walsenders are stuck
* We don't have a good way to detect stuck
# Discussion
Compared to physical replication, it is likely to happen that logical replication is stuck.
I think the risk should be avoided as much as possible by fixing codes.
Then, if it leads another failure, we can document the caution to users.
While shutting down the server, checkpointer sends SIGUSR1 signal to wansenders.
It is done after being exited other processes, so we cannot raise ERROR and rollback
the operation if checkpointer recognize the process stuck at that time.
We don't have any features that postmaster can check whether this node is
publisher or not. So if we want to add the mechanism that can check the health
of walsenders before shutting down, we must do that at the top of
process_pm_shutdown_request() even if we are not in logical replication.
I think it affects the basis of postgres largely, and in the first place,
PostgreSQL does not have a mechanism to check the health of process.
Therefore, I want to adopt the approach that walsender itself exits immediately when they get signals.
## About patch - Were fixes correct?
In ProcessPendingWrites(), my patch, wansender calls WalSndDone() when it gets
SIGUSR1 signal. I think this should be. From the patch [1]:
```
@@ -1450,6 +1450,10 @@ ProcessPendingWrites(void)
/* Try to flush pending output to the client */
if (pq_flush_if_writable() != 0)
WalSndShutdown();
+
+ /* If we got shut down requested, try to exit the process */
+ if (got_STOPPING)
+ WalSndDone(XLogSendLogical);
}
/* reactivate latch so WalSndLoop knows to continue */
```
Per my analysis, in case of logical replication, walsenders exit with following
steps. Note that logical walsender does not receive SIGUSR2 signal, set flag by
themselves instead:
1. postmaster sends shutdown requests to checkpointer
2. checkpointer sends SIGUSR1 to walsenders and wait
3. when walsenders accept SIGUSR1, they turn got_SIGUSR1 on.
4. walsenders consume all WALs. @XLogSendLogical
5. walsenders turn got_SIGUSR2 on by themselves @XLogSendLogical
6. walsenders recognize the flag is on, so call WalSndDone() @ WalSndLoop
7. proc_exit(0)
8. checkpoitner writes shutdown record
...
Type (i) stuck, I reported in -hackers[1], means that processes stop at step 6
and Type (ii) stuck means that processes stop at 4. In step4, got_SIGUSR2 is never set to on, so
we must use got_STOPPING flag.
[1]: https://www.postgresql.org/message-id/[email protected]....
Best Regards,
Hayato Kuroda
FUJITSU LIMITED
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2020-11-11 14:21 [PATCH v18 2/2] New command ALTER TABLE ALL IN TABLESPACE SET LOGGED/UNLOGGED Kyotaro Horiguchi <[email protected]>
2023-01-27 04:11 RE: Exit walsender before confirming remote flush in logical replication Hayato Kuroda (Fujitsu) <[email protected]>
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