0f5738202b
This speeds up obtaining hash values for GROUP BY and hashed SubPlans by using the ExprState support for hashing, thus allowing JIT compilation for obtaining hash values for these operations. This, even without JIT compilation, has been shown to improve Hash Aggregate performance in some cases by around 15% and hashed NOT IN queries in one case by over 30%, however, real-world cases are likely to see smaller gains as the test cases used were purposefully designed to have high hashing overheads by keeping the hash table small to prevent additional memory overheads that would be a factor when working with large hash tables. In passing, fix a hypothetical bug in ExecBuildHash32Expr() so that the initial value is stored directly in the ExprState's result field if there are no expressions to hash. None of the current users of this function use an initial value, so the bug is only hypothetical. Reviewed-by: Andrei Lepikhov <lepihov@gmail.com> Discussion: https://postgr.es/m/CAApHDvpYSO3kc9UryMevWqthTBrxgfd9djiAjKHMPUSQeX9vdQ@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/.