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Allow negative aggtransspace to indicate unbounded state size

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This patch reuses the existing aggtransspace in pg_aggregate to
signal that an aggregate's transition state can grow unboundedly.  If
aggtransspace is set to a negative value, it now indicates that the
transition state may consume unpredictable or large amounts of memory,
such as in aggregates like array_agg or string_agg that accumulate
input rows.

This information can be used by the planner to avoid applying
memory-sensitive optimizations (e.g., eager aggregation) when there is
a risk of excessive memory usage during partial aggregation.

Bump catalog version.

Per idea from Robert Haas, though applied differently than originally
suggested.

Discussion: https://postgr.es/m/CA+TgmoYbkvYwLa+1vOP7RDY7kO2=A7rppoPusoRXe44VDOGBPg@mail.gmail.com
This commit is contained in:
Richard Guo
2025-10-08 17:01:48 +09:00
parent 138da727a1
commit 185e304263
6 changed files with 21 additions and 11 deletions
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2
src/test/regress/expected/opr_sanity.out
View File

@@ -1470,7 +1470,7 @@ WHERE aggfnoid = 0 OR aggtransfn = 0 OR
(aggkind = 'n' AND aggnumdirectargs > 0) OR
aggfinalmodify NOT IN ('r', 's', 'w') OR
aggmfinalmodify NOT IN ('r', 's', 'w') OR
aggtranstype = 0 OR aggtransspace < 0 OR aggmtransspace < 0;
aggtranstype = 0 OR aggmtransspace < 0;
ctid | aggfnoid
------+----------
(0 rows)

2
src/test/regress/sql/opr_sanity.sql
View File

@@ -847,7 +847,7 @@ WHERE aggfnoid = 0 OR aggtransfn = 0 OR
(aggkind = 'n' AND aggnumdirectargs > 0) OR
aggfinalmodify NOT IN ('r', 's', 'w') OR
aggmfinalmodify NOT IN ('r', 's', 'w') OR
aggtranstype = 0 OR aggtransspace < 0 OR aggmtransspace < 0;
aggtranstype = 0 OR aggmtransspace < 0;
-- Make sure the matching pg_proc entry is sensible, too.