f36e82072c
The planner is in fact willing to use hash aggregation when work_mem is not set high enough for everything to fit in memory. This has been the case since commit 1f39bce0, which added disk-based hash aggregation. There are a few remaining cases in which hash aggregation is avoided as a matter of policy when the planner surmises that spilling will be necessary. For example, callers of choose_hashed_setop() still conservatively avoid hash aggregation when spilling is anticipated. That doesn't seem like a good enough reason to mention hash aggregation in this context. Backpatch: 13-, where disk-based hash aggregation was introduced.
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. PostgreSQL has many language interfaces, many of which are listed here: https://www.postgresql.org/download/ See the file INSTALL for instructions on how to build and install PostgreSQL. That file also lists supported operating systems and hardware platforms and contains information regarding any other software packages that are required to build or run the PostgreSQL system. Copyright and license information can be found in the file COPYRIGHT. A comprehensive documentation set is included in this distribution; it can be read as described in the installation instructions. The latest version of this software may be obtained at https://www.postgresql.org/download/. For more information look at our web site located at https://www.postgresql.org/.