From a767cdc84c9a4cba1f92854de55fb8b5f2de4598 Mon Sep 17 00:00:00 2001 From: Tom Lane Date: Wed, 27 Mar 2024 13:39:03 -0400 Subject: [PATCH] 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 62d028379b..3221fa1522 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); @@ -2785,7 +2785,7 @@ 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