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The planner has to special-case indexes on boolean columns, because what we need for an indexscan on such a column is a qual of the shape of "boolvar = pseudoconstant". For plain bool constants, previous simplification will have reduced this to "boolvar" or "NOT boolvar", and we have to reverse that if we want to make an indexqual. There is existing code to do so, but it only fires when the index's opfamily is BOOL_BTREE_FAM_OID or BOOL_HASH_FAM_OID. Thus extension AMs, or extension opclasses such as contrib/btree_gin, are out in the cold. The reason for hard-wiring the set of relevant opfamilies was mostly to avoid a catalog lookup in a hot code path. We can improve matters while not taking much of a performance hit by relying on the hard-wired set when the opfamily OID is visibly built-in, and only checking the catalogs when dealing with an extension opfamily. While here, rename IsBooleanOpfamily to IsBuiltinBooleanOpfamily to remind future users of that macro of its limitations. At some point we might want to make indxpath.c's improved version of the test globally accessible, but it's not presently needed elsewhere. Zongliang Quan and Tom Lane Discussion: https://postgr.es/m/f293b91d-1d46-d386-b6bb-4b06ff5c667b@yeah.net
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/.