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Up to now, there's been hard-wired assumptions that normal aggregates' final functions never modify their transition states, while ordered-set aggregates' final functions always do. This has always been a bit limiting, and in particular it's getting in the way of improving the built-in ordered-set aggregates to allow merging of transition states. Therefore, let's introduce catalog and CREATE AGGREGATE infrastructure that lets the finalfn's behavior be declared explicitly. There are now three possibilities for the finalfn behavior: it's purely read-only, it trashes the transition state irrecoverably, or it changes the state in such a way that no more transfn calls are possible but the state can still be passed to other, compatible finalfns. There are no examples of this third case today, but we'll shortly make the built-in OSAs act like that. This change allows user-defined aggregates to explicitly disclaim support for use as window functions, and/or to prevent transition state merging, if their implementations cannot handle that. While it was previously possible to handle the window case with a run-time error check, there was not any way to prevent transition state merging, which in retrospect is something commit 804163bc2 should have provided for. But better late than never. In passing, split out pg_aggregate.c's extern function declarations into a new header file pg_aggregate_fn.h, similarly to what we've done for some other catalog headers, so that pg_aggregate.h itself can be safe for frontend files to include. This lets pg_dump use the symbolic names for relevant constants. Discussion: https://postgr.es/m/4834.1507849699@sss.pgh.pa.us
PostgreSQL tests ================ This directory contains a variety of test infrastructure as well as some of the tests in PostgreSQL. Not all tests are here -- in particular, there are more in individual contrib/ modules and in src/bin. Not all these tests get run by "make check". Check src/test/Makefile to see which tests get run automatically. authentication/ Tests for authentication examples/ Demonstration programs for libpq that double as regression tests via "make check" isolation/ Tests for concurrent behavior at the SQL level locale/ Sanity checks for locale data, encodings, etc mb/ Tests for multibyte encoding (UTF-8) support modules/ Extensions used only or mainly for test purposes, generally not suitable for installing in production databases perl/ Infrastructure for Perl-based TAP tests recovery/ Test suite for recovery and replication regress/ PostgreSQL's main regression test suite, pg_regress ssl/ Tests to exercise and verify SSL certificate handling subscription/ Tests for logical replication thread/ A thread-safety-testing utility used by configure