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ALTER TABLE ... SET EXPRESSION AS removes statistics for the target column, so running ANALYZE afterward is recommended. But this was previously not documented, even though a similar recommendation exists for ALTER TABLE ... SET DATA TYPE, which also clears the column's statistics. This commit updates the documentation to include the ANALYZE recommendation for SET EXPRESSION AS. Since v18, virtual generated columns are supported, and these columns never have statistics. Therefore, ANALYZE is not needed after SET DATA TYPE or SET EXPRESSION AS when used on virtual generated columns. This commit also updates the documentation to clarify that ANALYZE is unnecessary in such cases. Back-patch the ANALYZE recommendation for SET EXPRESSION AS to v17 where the feature was introduced, and the note about virtual generated columns to v18 where those columns were added. Author: Yugo Nagata <nagata@sraoss.co.jp> Reviewed-by: Fujii Masao <masao.fujii@gmail.com> Discussion: https://postgr.es/m/20250804151418.0cf365bd2855d606763443fe@sraoss.co.jp Backpatch-through: 17
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/.