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Since we taught btree to handle ScalarArrayOpExpr quals natively (commit 9e8da0f75731aaa7605cf4656c21ea09e84d2eb1), the planner has always included ScalarArrayOpExpr quals in index conditions if possible. However, if the qual is for a non-first index column, this could result in an inferior plan because we can no longer take advantage of index ordering (cf. commit 807a40c551dd30c8dd5a0b3bd82f5bbb1e7fd285). It can be better to omit the ScalarArrayOpExpr qual from the index condition and let it be done as a filter, so that the output doesn't need to get sorted. Indeed, this is true for the query introduced as a test case by the latter commit. To fix, restructure get_index_paths and build_index_paths so that we consider paths both with and without ScalarArrayOpExpr quals in non-first index columns. Redesign the API of build_index_paths so that it reports what it found, saving useless second or third calls. Report and patch by Andrew Gierth (though rather heavily modified by me). Back-patch to 9.2 where this code was introduced, since the issue can result in significant performance regressions compared to plans produced by 9.1 and earlier.
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: http://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 http://www.postgresql.org/download/. For more information look at our web site located at http://www.postgresql.org/.