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Richard Guo a8ccf4e93a Reordering DISTINCT keys to match input path's pathkeys 
The ordering of DISTINCT items is semantically insignificant, so we
can reorder them as needed.  In fact, in the parser, we absorb the
sorting semantics of the sortClause as much as possible into the
distinctClause, ensuring that one clause is a prefix of the other.
This can help avoid a possible need to re-sort.

In this commit, we attempt to adjust the DISTINCT keys to match the
input path's pathkeys.  This can likewise help avoid re-sorting, or
allow us to use incremental-sort to save efforts.

For DISTINCT ON expressions, the parser already ensures that they
match the initial ORDER BY expressions.  When reordering the DISTINCT
keys, we must ensure that the resulting pathkey list matches the
initial distinctClause pathkeys.

This introduces a new GUC, enable_distinct_reordering, which allows
the optimization to be disabled if needed.

Author: Richard Guo
Reviewed-by: Andrei Lepikhov
Discussion: https://postgr.es/m/CAMbWs48dR26cCcX0f=8bja2JKQPcU64136kHk=xekHT9xschiQ@mail.gmail.com
2024-11-26 09:25:18 +09:00
..
access Revert pg_wal_replay_wait() stored procedure 2024-11-04 22:47:57 +02:00
archive Add macro for customizing an archiving WARNING message. 2024-03-04 15:41:42 -06:00
backup Align blocks in incremental backups to BLCKSZ 2024-04-05 16:30:01 +02:00
bootstrap Update copyright for 2024 2024-01-03 20:49:05 -05:00
catalog Add two attributes to pg_stat_database for parallel workers activity 2024-11-11 10:40:48 +09:00
commands doc: Add better description for rewrite functions in event triggers 2024-10-29 15:35:01 +09:00
common Unify src/common/'s definitions of MaxAllocSize. 2024-10-28 14:39:01 -04:00
datatype Update copyright for 2024 2024-01-03 20:49:05 -05:00
executor Fix NULLIF()'s handling of read-write expanded objects. 2024-11-25 18:09:09 -05:00
fe_utils pg_verifybackup: Verify tar-format backups. 2024-09-27 08:40:24 -04:00
foreign Clean up more indent breakage from 6377e12a5. 2024-04-16 13:00:40 -04:00
jit jit: Remove obsolete LLVM version guard. 2024-11-11 12:07:24 +13:00
lib Revert pg_wal_replay_wait() stored procedure 2024-11-04 22:47:57 +02:00
libpq Make the memory layout of Port struct independent of USE_OPENSSL 2024-11-22 17:43:04 +02:00
mb Inline basic UTF-8 functions. 2024-03-20 09:40:57 -07:00
nodes Add pg_constraint rows for not-null constraints 2024-11-08 13:28:48 +01:00
optimizer Reordering DISTINCT keys to match input path's pathkeys 2024-11-26 09:25:18 +09:00
parser Track more precisely query locations for nested statements 2024-10-24 09:29:54 +09:00
partitioning Revert support for ALTER TABLE ... MERGE/SPLIT PARTITION(S) commands 2024-08-24 18:48:48 +03:00
pch Update copyright for 2024 2024-01-03 20:49:05 -05:00
port Fix sign-compare warnings in pg_iovec.h. 2024-11-08 16:11:08 -06:00
portability Fix datatypes in comments in instr_time.h 2024-08-06 22:15:55 +03:00
postmaster Pass MyPMChildSlot as an explicit argument to child process 2024-11-14 16:12:32 +02:00
regex Avoid assertion due to disconnected NFA sub-graphs in regex parsing. 2024-11-15 18:23:38 -05:00
replication Doc: Clarify the inactive_since field description. 2024-11-25 11:12:32 +05:30
rewrite Support MERGE into updatable views. 2024-02-29 15:56:59 +00:00
snowball Update copyright for 2024 2024-01-03 20:49:05 -05:00
statistics Add functions pg_restore_relation_stats(), pg_restore_attribute_stats(). 2024-10-24 12:08:00 -07:00
storage Assign a child slot to every postmaster child process 2024-11-14 16:12:28 +02:00
tcop Restrict accesses to non-system views and foreign tables during pg_dump. 2024-08-05 06:05:33 -07:00
tsearch Constify fields and parameters in spell.c 2024-08-06 23:04:51 +03:00
utils Add write_to_file to PgStat_KindInfo for pgstats kinds 2024-11-22 10:12:26 +09:00
.gitignore Refactor dlopen() support 2018-09-06 11:33:04 +02:00
c.h Assume that <stdbool.h> conforms to the C standard. 2024-11-25 20:54:28 +13:00
fmgr.h Remove _PG_fini() 2024-08-21 07:24:03 +09:00
funcapi.h Update copyright for 2024 2024-01-03 20:49:05 -05:00
getopt_long.h Update copyright for 2024 2024-01-03 20:49:05 -05:00
Makefile Put genbki.pl output into src/include/catalog/ directly 2024-03-14 07:11:21 +01:00
meson.build meson: Restore implicit warning/debug/optimize flags for extensions 2024-06-07 09:36:26 +02:00
miscadmin.h Replace postmaster.c's own backend type codes with BackendType 2024-11-14 16:06:16 +02:00
pg_config.h.in Assume that <stdbool.h> conforms to the C standard. 2024-11-25 20:54:28 +13:00
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.meson meson: Add initial version of meson based build system 2022-09-21 22:37:17 -07:00
pg_config_manual.h Add prefetching support on macOS 2024-08-28 07:28:27 +02:00
pg_getopt.h Update copyright for 2024 2024-01-03 20:49:05 -05:00
pg_trace.h Update copyright for 2024 2024-01-03 20:49:05 -05:00
pgstat.h Add two attributes to pg_stat_database for parallel workers activity 2024-11-11 10:40:48 +09:00
pgtar.h Update copyright for 2024 2024-01-03 20:49:05 -05:00
pgtime.h Update copyright for 2024 2024-01-03 20:49:05 -05:00
port.h More use of getpwuid_r() directly 2024-09-02 09:04:30 +02:00
postgres.h Update copyright for 2024 2024-01-03 20:49:05 -05:00
postgres_ext.h Move RelFileNumber declarations to common/relpath.h. 2022-09-27 12:01:57 -04:00
postgres_fe.h Update copyright for 2024 2024-01-03 20:49:05 -05:00
varatt.h Update copyright for 2024 2024-01-03 20:49:05 -05:00
windowapi.h Update copyright for 2024 2024-01-03 20:49:05 -05:00