From: Richard Guo <rguo@postgresql.org>
To: pgsql-committers@lists.postgresql.org
Subject: pgsql: Allow negative aggtransspace to indicate unbounded state size
Date: Wed, 08 Oct 2025 08:06:06 +0000
Message-ID: <E1v6PBW-000dzm-2S@gemulon.postgresql.org> (raw)
Allow negative aggtransspace to indicate unbounded state size
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
Branch
------
master
Details
-------
https://git.postgresql.org/pg/commitdiff/185e304263347d0979832f7a08a812872d136b18
Modified Files
--------------
doc/src/sgml/catalogs.sgml | 5 ++++-
doc/src/sgml/ref/create_aggregate.sgml | 11 ++++++++---
src/include/catalog/catversion.h | 2 +-
src/include/catalog/pg_aggregate.dat | 10 ++++++----
src/test/regress/expected/opr_sanity.out | 2 +-
src/test/regress/sql/opr_sanity.sql | 2 +-
6 files changed, 21 insertions(+), 11 deletions(-)
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To: pgsql-committers@postgresql.org
Cc: rguo@postgresql.org, pgsql-committers@lists.postgresql.org
Subject: Re: pgsql: Allow negative aggtransspace to indicate unbounded state size
In-Reply-To: <E1v6PBW-000dzm-2S@gemulon.postgresql.org>
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