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When either inputs of an INTERSECT [ALL] operator are proven not to return any results (a dummy rel), then mark the entire INTERSECT operation as dummy. Likewise, if an EXCEPT [ALL] operation's left input is proven empty, then mark the entire operation as dummy. With EXCEPT ALL, we can easily handle the right input being dummy as we can return the left input without any processing. That can lead to significant performance gains during query execution. We can't easily handle dummy right inputs for EXCEPT (without ALL), as that would require deduplication of the left input. Wiring up those Paths is likely more complex than it's worth as the gains during execution aren't that great, so let's leave that one to be handled by the normal Path generation code. Author: David Rowley <dgrowleyml@gmail.com> Reviewed-by: Tom Lane <tgl@sss.pgh.pa.us> Discussion: https://postgr.es/m/CAApHDvri53PPF76c3M94_QNWbJfXjyCnjXuj_2=LYM-0m8WZtw@mail.gmail.com |
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| examples | ||
| icu | ||
| isolation | ||
| kerberos | ||
| ldap | ||
| locale | ||
| mb | ||
| modules | ||
| perl | ||
| postmaster | ||
| recovery | ||
| regress | ||
| ssl | ||
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| Makefile | ||
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| 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 (but see also below) examples/ Demonstration programs for libpq that double as regression tests via "make check" isolation/ Tests for concurrent behavior at the SQL level kerberos/ Tests for Kerberos/GSSAPI authentication and encryption ldap/ Tests for LDAP-based authentication 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