rdelaage/postgresql
1
0
Fork 0
mirror of https://git.postgresql.org/git/postgresql.git synced 2024-09-30 00:51:31 +02:00
Code Issues Packages Projects Releases Wiki Activity
30,829 Commits 36 Branches 606 Tags 423 MiB
C 86%
PLpgSQL 5.5%
Perl 4.1%
Yacc 1.3%
Makefile 0.7%
Other 2.3%
244407a710
Go to file
Tom Lane 244407a710 Fix efficiency problems in tuplestore_trim(). 
The original coding in tuplestore_trim() was only meant to work efficiently
in cases where each trim call deleted most of the tuples in the store.
Which, in fact, was the pattern of the original usage with a Material node
supporting mark/restore operations underneath a MergeJoin.  However,
WindowAgg now uses tuplestores and it has considerably less friendly
trimming behavior.  In particular it can attempt to trim one tuple at a
time off a large tuplestore.  tuplestore_trim() had O(N^2) runtime in this
situation because of repeatedly shifting its tuple pointer array.  Fix by
avoiding shifting the array until a reasonably large number of tuples have
been deleted.  This can waste some pointer space, but we do still reclaim
the tuples themselves, so the percentage wastage should be pretty small.

Per Jie Li's report of slow percent_rank() evaluation.  cume_dist() and
ntile() would certainly be affected as well, along with any other window
function that has a moving frame start and requires reading substantially
ahead of the current row.

Back-patch to 8.4, where window functions were introduced.  There's no
need to tweak it before that.
2010-12-10 11:33:38 -05:00
config Remove useless whitespace at end of lines 2010-11-23 22:34:55 +02:00
contrib Add KNNGIST support to contrib/pg_trgm. 2010-12-04 00:16:21 -05:00
doc Force default wal_sync_method to be fdatasync on Linux. 2010-12-08 20:01:09 -05:00
src Fix efficiency problems in tuplestore_trim(). 2010-12-10 11:33:38 -05:00
.gitignore Convert cvsignore to gitignore, and add .gitignore for build targets. 2010-09-22 12:57:04 +02:00
aclocal.m4 Remove cvs keywords from all files. 2010-09-20 22:08:53 +02:00
configure Add/fix caching on some configure checks 2010-09-29 22:38:04 +03:00
configure.in Remove useless whitespace at end of lines 2010-11-23 22:34:55 +02:00
COPYRIGHT
GNUmakefile.in Improved parallel make support 2010-11-12 22:15:16 +02:00
Makefile
README Remove useless whitespace at end of lines 2010-11-23 22:34:55 +02:00
README.git Trivial typo fix. 2010-09-21 14:16:00 -04:00

README 

PostgreSQL Database Management System
=====================================

This directory contains the source code distribution of the PostgreSQL
database management system.

PostgreSQL is an advanced object-relational database management system
that supports an extended subset of the SQL standard, including
transactions, foreign keys, subqueries, triggers, user-defined types
and functions.  This distribution also contains C language bindings.

PostgreSQL has many language interfaces, many of which are listed here:

	http://www.postgresql.org/download

See the file INSTALL for instructions on how to build and install
PostgreSQL.  That file also lists supported operating systems and
hardware platforms and contains information regarding any other
software packages that are required to build or run the PostgreSQL
system.  Changes between all PostgreSQL releases are recorded in the
file HISTORY.  Copyright and license information can be found in the
file COPYRIGHT.  A comprehensive documentation set is included in this
distribution; it can be read as described in the installation
instructions.

The latest version of this software may be obtained at
http://www.postgresql.org/download/.  For more information look at our
web site located at http://www.postgresql.org/.