e01b23b84e
We've long had enable_hashagg to discourage hashed aggregation, but there was no equivalent for grouping that works by reading presorted input. That's handy when investigating planner cost misestimates, and as an escape hatch when a sorted grouping plan is chosen over a much cheaper hashed one. enable_groupagg (on by default) covers the GroupAggregate and Group nodes, the sort-based Unique step used for DISTINCT and semijoin unique-ification, and the sorted mode of SetOp. It isn't a hard switch; it only bumps disabled_nodes, so plans with no other choice are still produced. Several regression and module tests had been setting enable_sort off, and one enable_indexscan off, only to force a hashed plan. Use enable_groupagg there instead, where that was the real intent. In union.sql this also lets us test the hashed UNION path, which we had no way to reach before. Author: Tatsuro Yamada <yamatattsu@gmail.com> Co-authored-by: Richard Guo <guofenglinux@gmail.com> Reviewed-by: Ashutosh Bapat <ashutosh.bapat.oss@gmail.com> Reviewed-by: David Rowley <dgrowleyml@gmail.com> Discussion: https://postgr.es/m/CAOKkKFvYHSEsFazkrf9bRH14p-H27XMaqbZfRYjS6EHBruvZMQ@mail.gmail.com |
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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/.