From 3fdd05e3c584efec56a049c501f1973735c15e66 Mon Sep 17 00:00:00 2001 From: Andrey Rachitskiy Date: Wed, 30 Sep 2026 18:04:07 +0500 Subject: [PATCH v2] Fix first_value, nth_value, and last_value with EXCLUDE TIES. WinGetFuncArgInFrame remaps the first overlapping peer to currentpos for EXCLUDE TIES, and the last overlapping peer when seeking from the frame tail. That is only valid when the current row is in the frame. With a ROWS frame that starts on a peer, such as 1 FOLLOWING AND UNBOUNDED FOLLOWING, the remap lands on the current row, which is then rejected as out of frame. first_value and nth_value return NULL even though later in-frame rows remain. last_value has the same hole when the frame ends on a peer. Aggregates over the same window already saw those rows, because they walk the frame with row_is_in_frame. If the current row is before the frame head, skip the overlapping peer group as EXCLUDE GROUP does. Do the same from the tail when the current row is at or after the frame tail. Author: Andrey Rachitskiy Reported-by: Shallow Discussion: https://www.postgresql.org/message-id/19732-d4eed889e3021ef8@postgresql.org --- src/backend/executor/nodeWindowAgg.c | 29 +++++++++++++++++----------- src/test/regress/expected/window.out | 23 ++++++++++++++++++++++ src/test/regress/sql/window.sql | 11 +++++++++++ 3 files changed, 52 insertions(+), 11 deletions(-) diff --git a/src/backend/executor/nodeWindowAgg.c b/src/backend/executor/nodeWindowAgg.c index b86dcbba055..0b41eb4739e 100644 --- a/src/backend/executor/nodeWindowAgg.c +++ b/src/backend/executor/nodeWindowAgg.c @@ -4062,11 +4062,8 @@ WinGetFuncArgInFrame(WindowObject winobj, int argno, * row's peer group from resulting in trying to fetch a row before * some previous mark position. * - * Note that in some corner cases such as current row being - * outside frame, these calculations are theoretically too simple, - * but it doesn't matter because we'll end up deciding the row is - * out of frame. We do not attempt to avoid fetching rows past - * end of frame; that would happen in some cases anyway. + * We do not attempt to avoid fetching rows past end of frame. + * That would happen in some cases anyway. */ switch (winstate->frameOptions & FRAMEOPTION_EXCLUSION) { @@ -4097,10 +4094,15 @@ WinGetFuncArgInFrame(WindowObject winobj, int argno, int64 overlapstart = Max(winstate->groupheadpos, winstate->frameheadpos); - if (abs_pos == overlapstart) - abs_pos = winstate->currentpos; + if (winstate->currentpos >= winstate->frameheadpos) + { + if (abs_pos == overlapstart) + abs_pos = winstate->currentpos; + else + abs_pos += winstate->grouptailpos - overlapstart - 1; + } else - abs_pos += winstate->grouptailpos - overlapstart - 1; + abs_pos += winstate->grouptailpos - overlapstart; } break; default: @@ -4163,10 +4165,15 @@ WinGetFuncArgInFrame(WindowObject winobj, int argno, int64 overlapend = Min(winstate->grouptailpos, winstate->frametailpos); - if (abs_pos == overlapend - 1) - abs_pos = winstate->currentpos; + if (winstate->currentpos < winstate->frametailpos) + { + if (abs_pos == overlapend - 1) + abs_pos = winstate->currentpos; + else + abs_pos -= overlapend - 1 - winstate->groupheadpos; + } else - abs_pos -= overlapend - 1 - winstate->groupheadpos; + abs_pos -= overlapend - winstate->groupheadpos; } update_frameheadpos(winstate); if (abs_pos < winstate->frameheadpos) diff --git a/src/test/regress/expected/window.out b/src/test/regress/expected/window.out index c0bde1c5eec..d64060a91b1 100644 --- a/src/test/regress/expected/window.out +++ b/src/test/regress/expected/window.out @@ -1037,6 +1037,29 @@ FROM tenk1 WHERE unique1 < 10; 7 | 7 | 3 (10 rows) +-- first_value/last_value with EXCLUDE TIES when the frame edge is a peer +SELECT k, first_value(k) OVER w +FROM (VALUES (0), (0), (1)) t(k) +WINDOW w AS (ORDER BY k ROWS BETWEEN 1 FOLLOWING AND UNBOUNDED FOLLOWING + EXCLUDE TIES); + k | first_value +---+------------- + 0 | 1 + 0 | 1 + 1 | +(3 rows) + +SELECT k, last_value(k) OVER w +FROM (VALUES (0), (1), (1)) t(k) +WINDOW w AS (ORDER BY k ROWS BETWEEN UNBOUNDED PRECEDING AND 1 PRECEDING + EXCLUDE TIES); + k | last_value +---+------------ + 0 | + 1 | 0 + 1 | 0 +(3 rows) + SELECT sum(unique1) over (rows between 2 preceding and 1 preceding), unique1, four FROM tenk1 WHERE unique1 < 10; diff --git a/src/test/regress/sql/window.sql b/src/test/regress/sql/window.sql index 8e6f92d94c7..e74c00d668f 100644 --- a/src/test/regress/sql/window.sql +++ b/src/test/regress/sql/window.sql @@ -235,6 +235,17 @@ SELECT last_value(unique1) over (ORDER BY four rows between current row and 2 fo unique1, four FROM tenk1 WHERE unique1 < 10; +-- first_value/last_value with EXCLUDE TIES when the frame edge is a peer +SELECT k, first_value(k) OVER w +FROM (VALUES (0), (0), (1)) t(k) +WINDOW w AS (ORDER BY k ROWS BETWEEN 1 FOLLOWING AND UNBOUNDED FOLLOWING + EXCLUDE TIES); + +SELECT k, last_value(k) OVER w +FROM (VALUES (0), (1), (1)) t(k) +WINDOW w AS (ORDER BY k ROWS BETWEEN UNBOUNDED PRECEDING AND 1 PRECEDING + EXCLUDE TIES); + SELECT sum(unique1) over (rows between 2 preceding and 1 preceding), unique1, four FROM tenk1 WHERE unique1 < 10; -- 2.53.0