From 1de468099d27f44c1998c9c2251cd2aefcfab524 Mon Sep 17 00:00:00 2001 From: Tom Lane Date: Tue, 30 Jun 2026 17:21:23 -0400 Subject: [PATCH] Disallow set-returning functions within window OVER clauses. MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit We previously allowed this, but it leads to odd behaviors, basically because putting a SRF there is inconsistent with the principle that a window function doesn't change the number of rows in the query result. There doesn't seem to be a strong reason to try to make such cases behave consistently. Users should put their SRFs in lateral FROM clauses instead. This issue has been sitting on the back burner for multiple years now, partially because it didn't seem wise to back-patch such a change. Let's squeeze it into v19 before it's too late. Bug: #17502 Bug: #19535 Reported-by: Daniel Farkaš Reported-by: Qifan Liu Author: Tom Lane Reviewed-by: David Rowley Discussion: https://postgr.es/m/17502-281a7aaacfaa872a@postgresql.org Discussion: https://postgr.es/m/19535-376081d7cc07c86d@postgresql.org Backpatch-through: 19 --- src/backend/parser/parse_func.c | 3 --- src/test/regress/expected/tsrf.out | 25 +++++++++++++++---------- src/test/regress/sql/tsrf.sql | 10 +++++++--- 3 files changed, 22 insertions(+), 16 deletions(-) diff --git a/src/backend/parser/parse_func.c b/src/backend/parser/parse_func.c index 9cdbaa542fe..a9b6be7203b 100644 --- a/src/backend/parser/parse_func.c +++ b/src/backend/parser/parse_func.c @@ -2700,9 +2700,6 @@ check_srf_call_placement(ParseState *pstate, Node *last_srf, int location) break; case EXPR_KIND_WINDOW_PARTITION: case EXPR_KIND_WINDOW_ORDER: - /* okay, these are effectively GROUP BY/ORDER BY */ - pstate->p_hasTargetSRFs = true; - break; case EXPR_KIND_WINDOW_FRAME_RANGE: case EXPR_KIND_WINDOW_FRAME_ROWS: case EXPR_KIND_WINDOW_FRAME_GROUPS: diff --git a/src/test/regress/expected/tsrf.out b/src/test/regress/expected/tsrf.out index c4f7b187f5b..005f1268f4b 100644 --- a/src/test/regress/expected/tsrf.out +++ b/src/test/regress/expected/tsrf.out @@ -267,7 +267,21 @@ ERROR: window function calls cannot contain set-returning function calls LINE 1: SELECT min(generate_series(1, 3)) OVER() FROM few; ^ HINT: You might be able to move the set-returning function into a LATERAL FROM item. --- SRFs are normally computed after window functions +--- ... nor in window definitions +SELECT sum(id) OVER (PARTITION BY generate_series(1, 3)) FROM few; +ERROR: set-returning functions are not allowed in window definitions +LINE 1: SELECT sum(id) OVER (PARTITION BY generate_series(1, 3)) FRO... + ^ +SELECT sum(id) OVER (ORDER BY generate_series(1, 3)) FROM few; +ERROR: set-returning functions are not allowed in window definitions +LINE 1: SELECT sum(id) OVER (ORDER BY generate_series(1, 3)) FROM fe... + ^ +SELECT sum(id) OVER (ROWS BETWEEN UNBOUNDED PRECEDING + AND generate_series(1, 3) FOLLOWING) FROM few; +ERROR: set-returning functions are not allowed in window definitions +LINE 2: AND generate_series(1, 3) FOLLOWING) FR... + ^ +-- SRFs are computed after window functions SELECT id,lag(id) OVER(), count(*) OVER(), generate_series(1,3) FROM few; id | lag | count | generate_series ----+-----+-------+----------------- @@ -282,15 +296,6 @@ SELECT id,lag(id) OVER(), count(*) OVER(), generate_series(1,3) FROM few; 3 | 2 | 3 | 3 (9 rows) --- unless referencing SRFs -SELECT SUM(count(*)) OVER(PARTITION BY generate_series(1,3) ORDER BY generate_series(1,3)), generate_series(1,3) g FROM few GROUP BY g; - sum | g ------+--- - 3 | 1 - 3 | 2 - 3 | 3 -(3 rows) - -- sorting + grouping SELECT few.dataa, count(*), min(id), max(id), generate_series(1,3) FROM few GROUP BY few.dataa ORDER BY 5, 1; dataa | count | min | max | generate_series diff --git a/src/test/regress/sql/tsrf.sql b/src/test/regress/sql/tsrf.sql index 7c22529a0db..8442ba9e743 100644 --- a/src/test/regress/sql/tsrf.sql +++ b/src/test/regress/sql/tsrf.sql @@ -82,10 +82,14 @@ SELECT sum((3 = ANY(SELECT lag(x) over(order by x) -- SRFs are not allowed in window function arguments, either SELECT min(generate_series(1, 3)) OVER() FROM few; --- SRFs are normally computed after window functions +--- ... nor in window definitions +SELECT sum(id) OVER (PARTITION BY generate_series(1, 3)) FROM few; +SELECT sum(id) OVER (ORDER BY generate_series(1, 3)) FROM few; +SELECT sum(id) OVER (ROWS BETWEEN UNBOUNDED PRECEDING + AND generate_series(1, 3) FOLLOWING) FROM few; + +-- SRFs are computed after window functions SELECT id,lag(id) OVER(), count(*) OVER(), generate_series(1,3) FROM few; --- unless referencing SRFs -SELECT SUM(count(*)) OVER(PARTITION BY generate_series(1,3) ORDER BY generate_series(1,3)), generate_series(1,3) g FROM few GROUP BY g; -- sorting + grouping SELECT few.dataa, count(*), min(id), max(id), generate_series(1,3) FROM few GROUP BY few.dataa ORDER BY 5, 1;