From 6c9f320853decdfe59853b113968d5700e116600 Mon Sep 17 00:00:00 2001 From: Ewan Young Date: Wed, 15 Jul 2026 18:54:16 +0800 Subject: [PATCH v2] Remove redundant null-treatment check in window function dedup Commit 25a30bbd423 (IGNORE NULLS / RESPECT NULLS for window functions) made ExecInitWindowAgg() treat two otherwise-equal window functions as duplicates only when their ignore_nulls settings also matched: if (i <= wfuncno && wfunc->ignore_nulls == perfunc[i].ignore_nulls) That extra term reads WindowStatePerFuncData.ignore_nulls, but the field was never populated when a per-function entry was filled in, so it stayed zero from palloc0_array(). Consequently a duplicate call carrying IGNORE NULLS or an explicit RESPECT NULLS never matched an identical earlier entry and was needlessly given its own per-function slot and evaluated twice. (Results stayed correct; this was a missed sharing, not a wrong answer.) The extra term is in fact redundant. WindowFunc.ignore_nulls is a plain scalar field with no pg_node_attr, so _equalWindowFunc() already compares it; the preceding equal() call therefore never matches two WindowFuncs that differ only in null treatment. If equal() matches, ignore_nulls necessarily matched too, so the term can never change the outcome, and WindowStatePerFuncData.ignore_nulls existed only to feed it. Rather than populate the shadow field, drop the redundant term and the field (and adjust the now-stale comment) and let equal() do the work. That fixes the same bug while removing the hand-maintained duplicate state that caused it, so it cannot silently drift again. --- 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 f1c524d00df..d6f004de01e 100644 --- a/src/backend/executor/nodeWindowAgg.c +++ b/src/backend/executor/nodeWindowAgg.c @@ -110,7 +110,6 @@ typedef struct WindowStatePerFuncData bool plain_agg; /* is it just a plain aggregate function? */ int aggno; /* if so, index of its WindowStatePerAggData */ - uint8 ignore_nulls; /* ignore nulls */ WindowObject winobj; /* object used in window function API */ } WindowStatePerFuncData; @@ -2738,8 +2737,9 @@ ExecInitWindowAgg(WindowAgg *node, EState *estate, int eflags) wfunc->winref, node->winref); /* - * Look for a previous duplicate window function, which needs the same - * ignore_nulls value + * Look for a previous duplicate window function. equal() compares + * ignore_nulls too, so a call differing only in its null treatment is + * correctly treated as a distinct function. */ for (i = 0; i <= wfuncno; i++) { @@ -2747,7 +2747,7 @@ ExecInitWindowAgg(WindowAgg *node, EState *estate, int eflags) !contain_volatile_functions((Node *) wfunc)) break; } - if (i <= wfuncno && wfunc->ignore_nulls == perfunc[i].ignore_nulls) + if (i <= wfuncno) { /* Found a match to an existing entry, so just mark it */ wfuncstate->wfuncno = i; -- 2.47.3