postgres.git / summary / log / commit / refs
commit a94f51a7bfc9e65ce3799d8cb12945bd596c5ba8
Author: Tom Lane <tgl@sss.pgh.pa.us>
Date: Wed Mar 27 17:39:03 2024 +0000
First released in: 17.0, 12.19, 13.15, 14.12, 15.7, 16.3
Fix unnecessary use of moving-aggregate mode with non-moving frame.
When a plain aggregate is used as a window function, and the window
frame start is specified as UNBOUNDED PRECEDING, the frame's head
cannot move so we do not need to use moving-aggregate mode. The check
for that was put into initialize_peragg(), failing to notice that
ExecInitWindowAgg() calls that function before it's filled in
winstate->frameOptions. Since makeNode() would have zeroed the field,
this didn't provoke uninitialized-value complaints, nor would the
erroneous decision have resulted in more than a little inefficiency.
Still, it's wrong, so move the initialization of
winstate->frameOptions earlier to make it work properly.
While here, also fix a thinko in a comment. Both errors crept in in
commit a9d9acbf2 which introduced the moving-aggregate mode.
Spotted by Vallimaharajan G. Back-patch to all supported branches.
Discussion: https://postgr.es/m/18e7f2a5167.fe36253866818.977923893562469143@zohocorp.com
src/backend/executor/nodeWindowAgg.c | 8 ++++----
1 file changed, 4 insertions(+), 4 deletions(-)
diff --git a/src/backend/executor/nodeWindowAgg.c b/src/backend/executor/nodeWindowAgg.c
index 310ac23e3a1..7b5707996c1 100644
--- a/src/backend/executor/nodeWindowAgg.c
+++ b/src/backend/executor/nodeWindowAgg.c
@@ -2399,6 +2399,9 @@ ExecInitWindowAgg(WindowAgg *node, EState *estate, int eflags)
winstate->ss.ps.state = estate;
winstate->ss.ps.ExecProcNode = ExecWindowAgg;
+ /* copy frame options to state node for easy access */
+ winstate->frameOptions = frameOptions;
+
/*
* Create expression contexts. We need two, one for per-input-tuple
* processing and one for per-output-tuple processing. We cheat a little
@@ -2649,9 +2652,6 @@ ExecInitWindowAgg(WindowAgg *node, EState *estate, int eflags)
/* Set the status to running */
winstate->status = WINDOWAGG_RUN;
- /* copy frame options to state node for easy access */
- winstate->frameOptions = frameOptions;
-
/* initialize frame bound offset expressions */
winstate->startOffset = ExecInitExpr((Expr *) node->startOffset,
(PlanState *) winstate);
@@ -2802,7 +2802,7 @@ initialize_peragg(WindowAggState *winstate, WindowFunc *wfunc,
/*
* Figure out whether we want to use the moving-aggregate implementation,
- * and collect the right set of fields from the pg_attribute entry.
+ * and collect the right set of fields from the pg_aggregate entry.
*
* It's possible that an aggregate would supply a safe moving-aggregate
* implementation and an unsafe normal one, in which case our hand is
[parent: f5d0e866404a]