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Base de données relationnelle
fe5d62951b
The planner has two optimizations that move a qual clause across a
grouping boundary: subquery_planner transfers HAVING clauses to WHERE
so they can be evaluated before aggregation, and qual_is_pushdown_safe
pushes outer restriction clauses into a subquery past its DISTINCT,
DISTINCT ON, window PARTITION BY, or set-operation grouping layer.
Both produce wrong results when the moved clause's equivalence
relation disagrees with the grouping's, since the clause then filters
rows the grouping would have merged.
The disagreement has two forms. A type may belong to multiple btree
opfamilies whose equality operators disagree (e.g. record_ops vs
record_image_ops); or the grouping may use a nondeterministic
collation, where comparing the column under a different collation, or
wrapping it in a function or operator, can distinguish values the
collation considers equal. Because we cannot prove an arbitrary
expression preserves that equality, a grouping column with a
nondeterministic collation is safe to push only as a direct operand of
a comparison under its own collation.
Fix both call sites through a shared walker parameterized by a
callback that maps each Var to the grouping equality operator for its
column (or InvalidOid for non-grouping Vars). For HAVING, the
callback recovers the SortGroupClause's eqop via the GROUP Var's
varattno, which requires running before flatten_group_exprs while
havingQual still contains GROUP Vars. For subquery pushdown, the
callback recovers the eqop from subquery->distinctClause, a window's
partitionClause, or any grouping node in the SetOperationStmt tree.
The walker fires only when there is an equivalence boundary to cross,
gated by either the existing UNSAFE_NOTIN_DISTINCTON_CLAUSE and
UNSAFE_NOTIN_PARTITIONBY_CLAUSE flags or by a recursive check for any
grouping node in the set-op tree.
Back-patch to v18 only. The HAVING half relies on the RTE_GROUP
mechanism introduced in v18 (commit
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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/18/. In particular, information about building PostgreSQL from the source code can be found at https://www.postgresql.org/docs/18/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/.