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Robert Haas d31e2a495b Teach ALTER TABLE .. SET DATA TYPE to avoid some table rewrites. 
When the old type is binary coercible to the new type and the using
clause does not change the column contents, we can avoid a full table
rewrite, though any indexes on the affected columns will still need
to be rebuilt.  This applies, for example, when changing a varchar
column to be of type text.

The prior coding assumed that the set of operations that force a
rewrite is identical to the set of operations that must be propagated
to tables making use of the affected table's rowtype.  This is
no longer true: even though the tuples in those tables wouldn't
need to be modified, the data type change invalidate indexes built
using those composite type columns.  Indexes on the table we're
actually modifying can be invalidated too, of course, but the
existing machinery is sufficient to handle that case.

Along the way, add some debugging messages that make it possible
to understand what operations ALTER TABLE is actually performing
in these cases.

Noah Misch and Robert Haas
2011-02-12 08:27:55 -05:00
config Per-column collation support 2011-02-08 23:04:18 +02:00
contrib Add support for multiple versions of an extension and ALTER EXTENSION UPDATE. 2011-02-11 21:25:57 -05:00
doc Teach ALTER TABLE .. SET DATA TYPE to avoid some table rewrites. 2011-02-12 08:27:55 -05:00
src Teach ALTER TABLE .. SET DATA TYPE to avoid some table rewrites. 2011-02-12 08:27:55 -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 Per-column collation support 2011-02-08 23:04:18 +02:00
configure.in Per-column collation support 2011-02-08 23:04:18 +02:00
COPYRIGHT Stamp copyrights for year 2011. 2011-01-01 13:18:15 -05:00
GNUmakefile.in Improved parallel make support 2010-11-12 22:15:16 +02:00
Makefile Add new make targets "world", "install-world" and "installcheck-world" to build, install and check just about everything. 2010-01-28 23:59:52 +00:00
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/.