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Forced cache invalidation (CLOBBER_CACHE_ALWAYS) has been impractical to use for testing in PostgreSQL because it's so slow and because it's toggled on/off only at build time. It is helpful when hunting bugs in any code that uses the sycache/relcache because causes cache invalidations to be injected whenever it would be possible for an invalidation to occur, whether or not one was really pending. Address this by providing run-time control over cache clobber behaviour using the new debug_invalidate_system_caches_always GUC. Support is not compiled in at all unless assertions are enabled or CLOBBER_CACHE_ENABLED is explicitly defined at compile time. It defaults to 0 if compiled in, so it has negligible effect on assert build performance by default. When support is compiled in, test code can now set debug_invalidate_system_caches_always=1 locally to a backend to test specific queries, functions, extensions, etc. Or tests can toggle it globally for a specific test case while retaining normal performance during test setup and teardown. For backwards compatibility with existing test harnesses and scripts, debug_invalidate_system_caches_always defaults to 1 if CLOBBER_CACHE_ALWAYS is defined, and to 3 if CLOBBER_CACHE_RECURSIVE is defined. CLOBBER_CACHE_ENABLED is now visible in pg_config_manual.h, as is the related RECOVER_RELATION_BUILD_MEMORY setting for the relcache. Author: Craig Ringer <craig.ringer@2ndquadrant.com> Discussion: https://www.postgresql.org/message-id/flat/CAMsr+YF=+ctXBZj3ywmvKNUjWpxmuTuUKuv-rgbHGX5i5pLstQ@mail.gmail.com
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/.