Tom Lane 8ec5429e2f Reduce "X = X" to "X IS NOT NULL", if it's easy to do so. ... If the operator is a strict btree equality operator, and X isn't volatile, then the clause must yield true for any non-null value of X, or null if X is null. At top level of a WHERE clause, we can ignore the distinction between false and null results, so it's valid to simplify the clause to "X IS NOT NULL". This is a useful improvement mainly because we'll get a far better selectivity estimate in most cases. Because such cases seldom arise in well-written queries, it is unappetizing to expend a lot of planner cycles looking for them ... but it turns out that there's a place we can shoehorn this in practically for free, because equivclass.c already has to detect and reject candidate equivalences of the form X = X. That doesn't catch every place that it would be valid to simplify to X IS NOT NULL, but it catches the typical case. Working harder doesn't seem justified. Patch by me, reviewed by Petr Jelinek Discussion: https://postgr.es/m/CAMjNa7cC4X9YR-vAJS-jSYCajhRDvJQnN7m2sLH1wLh-_Z2bsw@mail.gmail.com		2017-10-08 12:23:32 -04:00
..
access	Fix traversal of half-frozen update chains	2017-10-06 17:20:01 +02:00
bootstrap	Phase 2 of pgindent updates.	2017-06-21 15:19:25 -04:00
catalog	Copy information from the relcache instead of pointing to it.	2017-10-06 15:28:07 -04:00
commands	Allow multiple tables to be specified in one VACUUM or ANALYZE command.	2017-10-03 18:53:44 -04:00
common	Increase SCRAM salt length	2017-08-24 14:04:28 -04:00
datatype	Phase 2 of pgindent updates.	2017-06-21 15:19:25 -04:00
executor	Fix crash when logical decoding is invoked from a PL function.	2017-10-06 19:18:58 -04:00
fe_utils	Provide a test for variable existence in psql	2017-09-21 19:02:23 -04:00
foreign	Basic partition-wise join functionality.	2017-10-06 11:11:10 -04:00
lib	Remove pre-order and post-order traversal logic for red-black trees.	2017-09-10 13:19:11 -04:00
libpq	Allow custom search filters to be configured for LDAP auth	2017-09-12 09:49:04 -04:00
mb	Phase 3 of pgindent updates.	2017-06-21 15:35:54 -04:00
nodes	Basic partition-wise join functionality.	2017-10-06 11:11:10 -04:00
optimizer	Reduce "X = X" to "X IS NOT NULL", if it's easy to do so.	2017-10-08 12:23:32 -04:00
parser	Support arrays over domains.	2017-09-30 13:40:56 -04:00
port	Remove redundant stdint.h include.	2017-10-01 15:24:58 -07:00
portability	Phase 2 of pgindent updates.	2017-06-21 15:19:25 -04:00
postmaster	Add background worker type	2017-09-29 11:08:24 -04:00
regex	Phase 2 of pgindent updates.	2017-06-21 15:19:25 -04:00
replication	Fix race condition with unprotected use of a latch pointer variable.	2017-10-03 14:00:56 -04:00
rewrite	Teach map_partition_varattnos to handle whole-row expressions.	2017-08-03 11:21:29 -04:00
snowball	Phase 2 of pgindent updates.	2017-06-21 15:19:25 -04:00
statistics	Phase 2 of pgindent updates.	2017-06-21 15:19:25 -04:00
storage	Refactor new file permission handling	2017-09-23 10:16:18 -04:00
tcop	Phase 3 of pgindent updates.	2017-06-21 15:35:54 -04:00
tsearch	Assume wcstombs(), towlower(), and sibling functions are always present.	2017-09-22 11:00:58 -04:00
utils	Msvc doesn't know UINT16_MAX, replace with PG_UINT16_MAX.	2017-10-04 10:01:02 -07:00
.gitignore	Autoconfiscate selection of 64-bit int type for 64-bit large object API.	2012-10-07 21:52:43 -04:00
c.h	Assume wcstombs(), towlower(), and sibling functions are always present.	2017-09-22 11:00:58 -04:00
fmgr.h	Introduce 64-bit hash functions with a 64-bit seed.	2017-08-31 22:21:21 -04:00
funcapi.h	Phase 2 of pgindent updates.	2017-06-21 15:19:25 -04:00
getaddrinfo.h	Phase 2 of pgindent updates.	2017-06-21 15:19:25 -04:00
getopt_long.h	Phase 2 of pgindent updates.	2017-06-21 15:19:25 -04:00
Makefile	Add statistics subdirectory to Makefile.	2017-06-08 11:29:50 -04:00
miscadmin.h	Remove replacement selection sort.	2017-09-29 10:25:44 -04:00
pg_config.h.in	Extend & revamp pg_bswap.h infrastructure.	2017-09-29 17:24:39 -07:00
pg_config.h.win32	Extend & revamp pg_bswap.h infrastructure.	2017-09-29 17:24:39 -07:00
pg_config_ext.h.in	Autoconfiscate selection of 64-bit int type for 64-bit large object API.	2012-10-07 21:52:43 -04:00
pg_config_ext.h.win32	Autoconfiscate selection of 64-bit int type for 64-bit large object API.	2012-10-07 21:52:43 -04:00
pg_config_manual.h	Fix s/intidb/initdb/ typo.	2017-09-22 11:35:26 -07:00
pg_getopt.h	Phase 2 of pgindent updates.	2017-06-21 15:19:25 -04:00
pg_trace.h	Phase 2 of pgindent updates.	2017-06-21 15:19:25 -04:00
pgstat.h	Avoid use of non-portable strnlen() in pgstat_clip_activity().	2017-09-19 14:25:47 -07:00
pgtar.h	Phase 3 of pgindent updates.	2017-06-21 15:35:54 -04:00
pgtime.h	Phase 2 of pgindent updates.	2017-06-21 15:19:25 -04:00
port.h	Change pg_ctl to detect server-ready by watching status in postmaster.pid.	2017-06-28 17:31:32 -04:00
postgres.h	Phase 3 of pgindent updates.	2017-06-21 15:35:54 -04:00
postgres_ext.h	Phase 2 of pgindent updates.	2017-06-21 15:19:25 -04:00
postgres_fe.h	Phase 2 of pgindent updates.	2017-06-21 15:19:25 -04:00
rusagestub.h	Phase 2 of pgindent updates.	2017-06-21 15:19:25 -04:00
windowapi.h	Phase 2 of pgindent updates.	2017-06-21 15:19:25 -04:00