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Tom Lane ad434473eb This patch addresses some issues in TOAST compression strategy that 
were discussed last year, but we felt it was too late in the 8.3 cycle to
change the code immediately.  Specifically, the patch:

* Reduces the minimum datum size to be considered for compression from
256 to 32 bytes, as suggested by Greg Stark.

* Increases the required compression rate for compressed storage from
20% to 25%, again per Greg's suggestion.

* Replaces force_input_size (size above which compression is forced)
with a maximum size to be considered for compression.  It was agreed
that allowing large inputs to escape the minimum-compression-rate
requirement was not bright, and that indeed we'd rather have a knob
that acted in the other direction.  I set this value to 1MB for the
moment, but it could use some performance studies to tune it.

* Adds an early-failure path to the compressor as suggested by Jan:
if it's been unable to find even one compressible substring in the
first 1KB (parameterizable), assume we're looking at incompressible
input and give up.  (Possibly this logic can be improved, but I'll
commit it as-is for now.)

* Improves the toasting heuristics so that when we have very large
fields with attstorage 'x' or 'e', we will push those out to toast
storage before considering inline compression of shorter fields.
This also responds to a suggestion of Greg's, though my original
proposal for a solution was a bit off base because it didn't fix
the problem for large 'e' fields.

There was some discussion in the earlier threads of exposing some
of the compression knobs to users, perhaps even on a per-column
basis.  I have not done anything about that here.  It seems to me
that if we are changing around the parameters, we'd better get some
experience and be sure we are happy with the design before we set
things in stone by providing user-visible knobs.
2008-03-07 23:20:21 +00:00
config Backport fixed AC_FUNC_FSEEKO 2008-02-19 18:02:30 +00:00
contrib Replace time_t with pg_time_t (same values, but always int64) in on-disk 2008-02-17 02:09:32 +00:00
doc Add: 2008-03-07 20:38:59 +00:00
src This patch addresses some issues in TOAST compression strategy that 2008-03-07 23:20:21 +00:00
aclocal.m4
configure Use our own getopt() and getopt_long() on Solaris, because that platform's 2008-02-24 05:21:54 +00:00
configure.in Use our own getopt() and getopt_long() on Solaris, because that platform's 2008-02-24 05:21:54 +00:00
COPYRIGHT Update copyrights in source tree to 2008. 2008-01-01 19:46:01 +00:00
GNUmakefile.in Replace useless uses of := by = in makefiles. 2007-02-09 15:56:00 +00:00
Makefile
README Update libpqxx URL in top-level README, per Gurjeet Singh. 2008-03-05 17:04:24 +00:00
README.CVS

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 including some of the more
common listed below:

C++ - http://pqxx.org/development/libpqxx/
JDBC - http://jdbc.postgresql.org
ODBC - http://odbc.postgresql.org
Perl - http://search.cpan.org/~dbdpg/
PHP - http://www.php.net
Python - http://www.initd.org/
Ruby - http://ruby.scripting.ca/postgres/

Other language binding are available from a variety of contributing
parties.

PostgreSQL also has a great number of procedural languages available,
a short, incomplete list is below:

PL/pgSQL - included in PostgreSQL source distribution
PL/Perl - included in PostgreSQL source distribution
PL/PHP - http://projects.commandprompt.com/projects/public/plphp
PL/Python - included in PostgreSQL source distribution
PL/Java - http://pgfoundry.org/projects/pljava/
PL/Tcl - included in PostgreSQL source distribution

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/.