mirror of
https://git.postgresql.org/git/postgresql.git
synced 2024-09-28 22:51:53 +02:00
25a9e54d2d
Formerly we only applied extended statistics to an OR clause as part of the clauselist_selectivity() code path for an OR clause appearing in an implicitly-ANDed list of clauses. This meant that it could only use extended statistics if all sub-clauses of the OR clause were covered by a single extended statistics object. Instead, teach clause_selectivity() how to apply extended statistics to an OR clause by handling its ORed list of sub-clauses in a similar manner to an implicitly-ANDed list of sub-clauses, but with different combination rules. This allows one or more extended statistics objects to be used to estimate all or part of the list of sub-clauses. Any remaining sub-clauses are then treated as if they are independent. Additionally, to avoid double-application of extended statistics, this introduces "extended" versions of clause_selectivity() and clauselist_selectivity(), which include an option to ignore extended statistics. This replaces the old clauselist_selectivity_simple() function which failed to completely ignore extended statistics when called from the extended statistics code. A known limitation of the current infrastructure is that an AND clause under an OR clause is not treated as compatible with extended statistics (because we don't build RestrictInfos for such sub-AND clauses). Thus, for example, "(a=1 AND b=1) OR (a=2 AND b=2)" will currently be treated as two independent AND clauses (each of which may be estimated using extended statistics), but extended statistics will not currently be used to account for any possible overlap between those clauses. Improving that is left as a task for the future. Original patch by Tomas Vondra, with additional improvements by me. Discussion: https://postgr.es/m/20200113230008.g67iyk4cs3xbnjju@development |
||
|---|---|---|
| config | ||
| contrib | ||
| doc | ||
| src | ||
| .dir-locals.el | ||
| .editorconfig | ||
| .gitattributes | ||
| .gitignore | ||
| aclocal.m4 | ||
| configure | ||
| configure.ac | ||
| COPYRIGHT | ||
| GNUmakefile.in | ||
| HISTORY | ||
| Makefile | ||
| README | ||
| README.git | ||
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/.