postgres

History

Peter Geoghegan dd299df818 Make heap TID a tiebreaker nbtree index column. Make nbtree treat all index tuples as having a heap TID attribute. Index searches can distinguish duplicates by heap TID, since heap TID is always guaranteed to be unique. This general approach has numerous benefits for performance, and is prerequisite to teaching VACUUM to perform "retail index tuple deletion". Naively adding a new attribute to every pivot tuple has unacceptable overhead (it bloats internal pages), so suffix truncation of pivot tuples is added. This will usually truncate away the "extra" heap TID attribute from pivot tuples during a leaf page split, and may also truncate away additional user attributes. This can increase fan-out, especially in a multi-column index. Truncation can only occur at the attribute granularity, which isn't particularly effective, but works well enough for now. A future patch may add support for truncating "within" text attributes by generating truncated key values using new opclass infrastructure. Only new indexes (BTREE_VERSION 4 indexes) will have insertions that treat heap TID as a tiebreaker attribute, or will have pivot tuples undergo suffix truncation during a leaf page split (on-disk compatibility with versions 2 and 3 is preserved). Upgrades to version 4 cannot be performed on-the-fly, unlike upgrades from version 2 to version 3. contrib/amcheck continues to work with version 2 and 3 indexes, while also enforcing stricter invariants when verifying version 4 indexes. These stricter invariants are the same invariants described by "3.1.12 Sequencing" from the Lehman and Yao paper. A later patch will enhance the logic used by nbtree to pick a split point. This patch is likely to negatively impact performance without smarter choices around the precise point to split leaf pages at. Making these two mostly-distinct sets of enhancements into distinct commits seems like it might clarify their design, even though neither commit is particularly useful on its own. The maximum allowed size of new tuples is reduced by an amount equal to the space required to store an extra MAXALIGN()'d TID in a new high key during leaf page splits. The user-facing definition of the "1/3 of a page" restriction is already imprecise, and so does not need to be revised. However, there should be a compatibility note in the v12 release notes. Author: Peter Geoghegan Reviewed-By: Heikki Linnakangas, Alexander Korotkov Discussion: https://postgr.es/m/CAH2-WzkVb0Kom=R+88fDFb=JSxZMFvbHVC6Mn9LJ2n=X=kS-Uw@mail.gmail.com		6 years ago
..
adminpack	Update copyright for 2019	7 years ago
amcheck	Make heap TID a tiebreaker nbtree index column.	6 years ago
auth_delay	Update copyright for 2019	7 years ago
auto_explain	Update copyright for 2019	7 years ago
bloom	Refactor index cost estimation functions in view of IndexClause changes.	6 years ago
btree_gin	Provide separate header file for built-in float types	7 years ago
btree_gist	Change floating-point output format for improved performance.	6 years ago
citext	Move hash_any prototype from access/hash.h to utils/hashutils.h	6 years ago
cube	Change floating-point output format for improved performance.	6 years ago
dblink	Remove superfluous tqual.h includes.	7 years ago
dict_int	Update copyright for 2019	7 years ago
dict_xsyn	Update copyright for 2019	7 years ago
earthdistance	Fix earthdistance test suite function name typo.	7 years ago
file_fdw	Split create_foreignscan_path() into three functions.	6 years ago
fuzzystrmatch	Update copyright for 2019	7 years ago
hstore	Move hash_any prototype from access/hash.h to utils/hashutils.h	6 years ago
hstore_plperl	Still further rethinking of build changes for macOS Mojave.	7 years ago
hstore_plpython	Fix volatile vs. pointer confusion	6 years ago
intagg	Schema-qualify some references to regprocedure.	9 years ago
intarray	Make use of compiler builtins and/or assembly for CLZ, CTZ, POPCNT.	6 years ago
isn	Update copyright for 2019	7 years ago
jsonb_plperl	Still further rethinking of build changes for macOS Mojave.	7 years ago
jsonb_plpython	Fix volatile vs. pointer confusion	6 years ago
lo	lo: Add test suite	8 years ago
ltree	Make use of compiler builtins and/or assembly for CLZ, CTZ, POPCNT.	6 years ago
ltree_plpython	Fix out-of-tree build for transform modules.	7 years ago
oid2name	Replace @postgresql.org with @lists.postgresql.org for mailinglists	7 years ago
pageinspect	Make heap TID a tiebreaker nbtree index column.	6 years ago
passwordcheck	Update copyright for 2019	7 years ago
pg_buffercache	Remove WITH OIDS support, change oid catalog column visibility.	7 years ago
pg_freespacemap	Replace heapam.h includes with {table, relation}.h where applicable.	7 years ago
pg_prewarm	Don't auto-restart per-database autoprewarm workers.	6 years ago
pg_standby	Replace @postgresql.org with @lists.postgresql.org for mailinglists	7 years ago
pg_stat_statements	Move hash_any prototype from access/hash.h to utils/hashutils.h	6 years ago
pg_trgm	Make use of compiler builtins and/or assembly for CLZ, CTZ, POPCNT.	6 years ago
pg_visibility	Move remaining code from tqual.[ch] to heapam.h / heapam_visibility.c.	7 years ago
pgcrypto	Suppress another case of MSVC warning 4146.	6 years ago
pgrowlocks	tableam: Add and use scan APIs.	6 years ago
pgstattuple	Make heap TID a tiebreaker nbtree index column.	6 years ago
postgres_fdw	Use slots in trigger infrastructure, except for the actual invocation.	6 years ago
seg	Change floating-point output format for improved performance.	6 years ago
sepgsql	Move hash_any prototype from access/hash.h to utils/hashutils.h	6 years ago
spi	Remove timetravel extension.	7 years ago
sslinfo	Phase 3 of pgindent updates.	8 years ago
start-scripts	Remove contrib/start-scripts/osx/.	8 years ago
tablefunc	Update copyright for 2019	7 years ago
tcn	Update copyright for 2019	7 years ago
test_decoding	Relax overly strict assertion	6 years ago
tsm_system_rows	tableam: Add and use scan APIs.	6 years ago
tsm_system_time	tableam: Add and use scan APIs.	6 years ago
unaccent	Add combining characters to unaccent.rules.	7 years ago
uuid-ossp	Update copyright for 2019	7 years ago
vacuumlo	Remove leftover reference to oid column.	6 years ago
xml2	Phase 3 of pgindent updates.	8 years ago
Makefile	Transforms for jsonb to PL/Perl	7 years ago
README	Rename 'gmake' to 'make' in docs and recommended commands	12 years ago
contrib-global.mk	Respect TEMP_CONFIG when pg_regress_check and friends are called	9 years ago

README

The PostgreSQL contrib tree
---------------------------

This subtree contains porting tools, analysis utilities, and plug-in
features that are not part of the core PostgreSQL system, mainly
because they address a limited audience or are too experimental to be
part of the main source tree.  This does not preclude their
usefulness.

User documentation for each module appears in the main SGML
documentation.

When building from the source distribution, these modules are not
built automatically, unless you build the "world" target.  You can
also build and install them all by running "make all" and "make
install" in this directory; or to build and install just one selected
module, do the same in that module's subdirectory.

Some directories supply new user-defined functions, operators, or
types.  To make use of one of these modules, after you have installed
the code you need to register the new SQL objects in the database
system by executing a CREATE EXTENSION command.  In a fresh database,
you can simply do

    CREATE EXTENSION module_name;

See the PostgreSQL documentation for more information about this
procedure.