mirror of
https://github.com/postgres/postgres.git
synced 2026-03-01 12:50:55 -05:00
7ca25b7de6
Previously, this function estimated the selectivity as 1 minus eqjoinsel() for the negator equality operator, regardless of join type (I think there was an expectation that eqjoinsel would handle the join type). But actually this is completely wrong for semijoin cases: the fraction of the LHS that has a non-matching row is not one minus the fraction of the LHS that has a matching row. In reality a semijoin with <> will nearly always succeed: it can only fail when the RHS is empty, or it contains a single distinct value that is equal to the particular LHS value, or the LHS value is null. The only one of those things we should have much confidence in estimating is the fraction of LHS values that are null, so let's just take the selectivity as 1 minus outer nullfrac. Per coding convention, antijoin should be estimated the same as semijoin. Arguably this is a bug fix, but in view of the lack of field complaints and the risk of destabilizing plans, no back-patch. Thomas Munro, reviewed by Ashutosh Bapat Discussion: https://postgr.es/m/CAEepm=270ze2hVxWkJw-5eKzc3AB4C9KpH3L2kih75R5pdSogg@mail.gmail.com |
||
|---|---|---|
| .. | ||
| authentication | ||
| examples | ||
| isolation | ||
| ldap | ||
| locale | ||
| mb | ||
| modules | ||
| perl | ||
| recovery | ||
| regress | ||
| ssl | ||
| subscription | ||
| thread | ||
| Makefile | ||
| README | ||
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