postgres

History

Tom Lane 9fa6f00b13 Rethink MemoryContext creation to improve performance. This patch makes a number of interrelated changes to reduce the overhead involved in creating/deleting memory contexts. The key ideas are: * Include the AllocSetContext header of an aset.c context in its first malloc request, rather than allocating it separately in TopMemoryContext. This means that we now always create an initial or "keeper" block in an aset, even if it never receives any allocation requests. * Create freelists in which we can save and recycle recently-destroyed asets (this idea is due to Robert Haas). * In the common case where the name of a context is a constant string, just store a pointer to it in the context header, rather than copying the string. The first change eliminates a palloc/pfree cycle per context, and also avoids bloat in TopMemoryContext, at the price that creating a context now involves a malloc/free cycle even if the context never receives any allocations. That would be a loser for some common usage patterns, but recycling short-lived contexts via the freelist eliminates that pain. Avoiding copying constant strings not only saves strlen() and strcpy() overhead, but is an essential part of the freelist optimization because it makes the context header size constant. Currently we make no attempt to use the freelist for contexts with non-constant names. (Perhaps someday we'll need to think harder about that, but in current usage, most contexts with custom names are long-lived anyway.) The freelist management in this initial commit is pretty simplistic, and we might want to refine it later --- but in common workloads that will never matter because the freelists will never get full anyway. To create a context with a non-constant name, one is now required to call AllocSetContextCreateExtended and specify the MEMCONTEXT_COPY_NAME option. AllocSetContextCreate becomes a wrapper macro, and it includes a test that will complain about non-string-literal context name parameters on gcc and similar compilers. An unfortunate side effect of making AllocSetContextCreate a macro is that one is now required to use the size parameter abstraction macros (ALLOCSET_DEFAULT_SIZES and friends) with it; the pre-9.6 habit of writing out individual size parameters no longer works unless you switch to AllocSetContextCreateExtended. Internally to the memory-context-related modules, the context creation APIs are simplified, removing the rather baroque original design whereby a context-type module called mcxt.c which then called back into the context-type module. That saved a bit of code duplication, but not much, and it prevented context-type modules from exercising control over the allocation of context headers. In passing, I converted the test-and-elog validation of aset size parameters into Asserts to save a few more cycles. The original thought was that callers might compute size parameters on the fly, but in practice nobody does that, so it's useless to expend cycles on checking those numbers in production builds. Also, mark the memory context method-pointer structs "const", just for cleanliness. Discussion: https://postgr.es/m/2264.1512870796@sss.pgh.pa.us		8 years ago
..
adminpack	Clean up assorted messiness around AllocateDir() usage.	8 years ago
amcheck	Rethink MemoryContext creation to improve performance.	8 years ago
auth_delay	Phase 3 of pgindent updates.	8 years ago
auto_explain	Phase 3 of pgindent updates.	8 years ago
bloom	Tighten test in contrib/bloom/t/001_wal.pl.	8 years ago
btree_gin	Phase 3 of pgindent updates.	8 years ago
btree_gist	Consistently use PG_INT(16\|32\|64)_(MIN\|MAX).	8 years ago
citext	Disable multi-byte citext tests	8 years ago
cube	Support index-only scans in contrib/cube and contrib/seg GiST indexes.	8 years ago
dblink	Change TRUE/FALSE to true/false	8 years ago
dict_int	Update copyright via script for 2017	9 years ago
dict_xsyn	Add some const decorations to prototypes	8 years ago
earthdistance	Phase 3 of pgindent updates.	8 years ago
file_fdw	Change TRUE/FALSE to true/false	8 years ago
fuzzystrmatch	Update typedefs.list and re-run pgindent	8 years ago
hstore	Avoid formally-undefined use of memcpy() in hstoreUniquePairs().	8 years ago
hstore_plperl	Make DatumGetFoo/PG_GETARG_FOO/PG_RETURN_FOO macro names more consistent.	8 years ago
hstore_plpython	Consistently catch errors from Python _New() functions	8 years ago
intagg	Schema-qualify some references to regprocedure.	9 years ago
intarray	Change TRUE/FALSE to true/false	8 years ago
isn	Update typedefs.list and re-run pgindent	8 years ago
lo	lo: Add test suite	8 years ago
ltree	Change TRUE/FALSE to true/false	8 years ago
ltree_plpython	Consistently catch errors from Python _New() functions	8 years ago
oid2name	Phase 3 of pgindent updates.	8 years ago
pageinspect	Change tupledesc->attrs[n] to TupleDescAttr(tupledesc, n).	8 years ago
passwordcheck	Simplify new test suite handling of passwordcheck	8 years ago
pg_buffercache	Phase 2 of pgindent updates.	8 years ago
pg_freespacemap	Default monitoring roles	8 years ago
pg_prewarm	Add background worker type	8 years ago
pg_standby	Fix assorted infelicities in new SetWALSegSize() function.	8 years ago
pg_stat_statements	pg_stat_statements: Add a comment about the dangers of padding bytes.	8 years ago
pg_trgm	Make pg_trgm tests independ from standard_conforming_string. Tests uses	8 years ago
pg_visibility	Phase 3 of pgindent updates.	8 years ago
pgcrypto	Add some const decorations to prototypes	8 years ago
pgrowlocks	Teach pgrowlocks to check relkind before scanning	8 years ago
pgstattuple	Minor code-cleanliness improvements for btree.	8 years ago
postgres_fdw	postgres_fdw: Fix failing regression test.	8 years ago
seg	Support index-only scans in contrib/cube and contrib/seg GiST indexes.	8 years ago
sepgsql	Phase 3 of pgindent updates.	8 years ago
spi	Document and use SPI_result_code_string()	8 years ago
sslinfo	Phase 3 of pgindent updates.	8 years ago
start-scripts	Remove contrib/start-scripts/osx/.	8 years ago
tablefunc	Change tupledesc->attrs[n] to TupleDescAttr(tupledesc, n).	8 years ago
tcn	Change tupledesc->attrs[n] to TupleDescAttr(tupledesc, n).	8 years ago
test_decoding	Fix crash when logical decoding is invoked from a PL function.	8 years ago
tsm_system_rows	Update copyright via script for 2017	9 years ago
tsm_system_time	Update copyright via script for 2017	9 years ago
unaccent	Add some const decorations to prototypes	8 years ago
uuid-ossp	Add some const decorations to prototypes	8 years ago
vacuumlo	Initial pgindent run with pg_bsd_indent version 2.0.	8 years ago
xml2	Phase 3 of pgindent updates.	8 years ago
Makefile	Remove contrib/chkpass	8 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.