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Hashing of a single Var is a very common operation for ExprState to perform. Here we add dedicated ExecJust* functions which helps speed up Hash Joins by removing the interpretation overhead in ExecInterpExpr(). This change currently only affects Hash Joins on a single column. Hash Joins with multiple join keys or an expression still run through ExecInterpExpr(). Some testing has shown up to 10% query performance increases on recent AMD hardware and nearly 7% increase on an Apple M2 for a query performing a hash join with a large number of lookups on a small hash table. This change was extracted from a larger patch which adjusts GROUP BY / hashed subplans / hashed set operations to use ExprState hashing. Discussion: https://postgr.es/m/CAApHDvr8Zc0ZgzVoCZLdHGOFNhiJeQ6vrUcS9V7N23zMWQb-eA@mail.gmail.com
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/.