787514b30b
custom_query_jumble (introduced in5ac462e2b7as a node field attribute) is now assigned to the expanded reference name "eref" of RangeTblEntry, adding in the query jumble computation the non-qualified aliased relation name, without the list of column names. The relation OID is removed from the query jumbling. The effects of this change can be seen in the tests added by3430215fe3, where pg_stat_statements (PGSS) entries are now grouped using the relation name, ignoring the relation search_path may point at. For example, these two relations are different, but are now grouped in a single PGSS entry as they are assigned the same query ID: CREATE TABLE foo1.tab (a int); CREATE TABLE foo2.tab (b int); SET search_path = 'foo1'; SELECT count(*) FROM tab; SET search_path = 'foo2'; SELECT count(*) FROM tab; SELECT count(*) FROM foo1.tab; SELECT count(*) FROM foo2.tab; SELECT query, calls FROM pg_stat_statements WHERE query ~ 'FROM tab'; query | calls --------------------------+------- SELECT count(*) FROM tab | 4 (1 row) It is still possible to use an alias in the FROM clause to split these. This behavior is useful for relations re-created with the same name, where queries based on such relations would be grouped in the same PGSS entry. For permanent schemas, it should not really matter in practice. The main benefit is for workloads that use a lot of temporary relations, which are usually re-created with the same name continuously. These can be a heavy source of bloat in PGSS depending on the workload. Such entries can now be grouped together, improving the user experience. The original idea from Christoph Berg used catalog lookups to find temporary relations, something that the query jumble has never done, and it could cause some performance regressions. The idea to use RangeTblEntry.eref and the relation name, applying the same rules for all relations, temporary and not temporary, has been proposed by Tom Lane. The documentation additions have been suggested by Sami Imseih. Author: Michael Paquier <michael@paquier.xyz> Co-authored-by: Sami Imseih <samimseih@gmail.com> Reviewed-by: Christoph Berg <myon@debian.org> Reviewed-by: Lukas Fittl <lukas@fittl.com> Reviewed-by: Sami Imseih <samimseih@gmail.com> Discussion: https://postgr.es/m/Z9iWXKGwkm8RAC93@msg.df7cb.de
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/.