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Mirror of the official PostgreSQL GIT repository. Note that this is just a *mirror* - we don't work with pull requests on github. To contribute, please see https://wiki.postgresql.org/wiki/Submitting_a_Patch
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Richard Guo e2debb6438 Reduce "Var IS [NOT] NULL" quals during constant folding 
In commit b262ad440, we introduced an optimization that reduces an IS
[NOT] NULL qual on a NOT NULL column to constant true or constant
false, provided we can prove that the input expression of the NullTest
is not nullable by any outer joins or grouping sets.  This deduction
happens quite late in the planner, during the distribution of quals to
rels in query_planner.  However, this approach has some drawbacks: we
can't perform any further folding with the constant, and it turns out
to be prone to bugs.

Ideally, this deduction should happen during constant folding.
However, the per-relation information about which columns are defined
as NOT NULL is not available at that point.  This information is
currently collected from catalogs when building RelOptInfos for base
or "other" relations.

This patch moves the collection of NOT NULL attribute information for
relations before pull_up_sublinks, storing it in a hash table keyed by
relation OID.  It then uses this information to perform the NullTest
deduction for Vars during constant folding.  This also makes it
possible to leverage this information to pull up NOT IN subqueries.

Note that this patch does not get rid of restriction_is_always_true
and restriction_is_always_false.  Removing them would prevent us from
reducing some IS [NOT] NULL quals that we were previously able to
reduce, because (a) the self-join elimination may introduce new IS NOT
NULL quals after constant folding, and (b) if some outer joins are
converted to inner joins, previously irreducible NullTest quals may
become reducible.

Author: Richard Guo <guofenglinux@gmail.com>
Reviewed-by: Robert Haas <robertmhaas@gmail.com>
Reviewed-by: Tom Lane <tgl@sss.pgh.pa.us>
Discussion: https://postgr.es/m/CAMbWs4-bFJ1At4btk5wqbezdu8PLtQ3zv-aiaY3ry9Ymm=jgFQ@mail.gmail.com
2025-07-22 11:21:36 +09:00
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contrib Reduce "Var IS [NOT] NULL" quals during constant folding 2025-07-22 11:21:36 +09:00
doc doc: Document reopen of output file via SIGHUP in pg_recvlogical. 2025-07-20 11:58:31 +09:00
src Reduce "Var IS [NOT] NULL" quals during constant folding 2025-07-22 11:21:36 +09:00
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README.md

PostgreSQL Database Management System

This directory contains the source code distribution of the PostgreSQL database management system.

PostgreSQL is an advanced object-relational database management system that supports an extended subset of the SQL standard, including transactions, foreign keys, subqueries, triggers, user-defined types and functions. This distribution also contains C language bindings.

Copyright and license information can be found in the file COPYRIGHT.

General documentation about this version of PostgreSQL can be found at https://www.postgresql.org/docs/devel/. In particular, information about building PostgreSQL from the source code can be found at https://www.postgresql.org/docs/devel/installation.html.

The latest version of this software, and related software, may be obtained at https://www.postgresql.org/download/. For more information look at our web site located at https://www.postgresql.org/.