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Heikki Linnakangas 47ad79122b Fix bugs in Serializable Snapshot Isolation.
Change the way UPDATEs are handled. Instead of maintaining a chain of
tuple-level locks in shared memory, copy any existing locks on the old
tuple to the new tuple at UPDATE. Any existing page-level lock needs to
be duplicated too, as a lock on the new tuple. That was neglected
previously.

Store xmin on tuple-level predicate locks, to distinguish a lock on an old
already-recycled tuple from a new tuple at the same physical location.
Failure to distinguish them caused loops in the tuple-lock chains, as
reported by YAMAMOTO Takashi. Although we don't use the chain representation
of UPDATEs anymore, it seems like a good idea to store the xmin to avoid
some false positives if no other reason.

CheckSingleTargetForConflictsIn now correctly handles the case where a lock
that's being held is not reflected in the local lock table. That happens
if another backend acquires a lock on our behalf due to an UPDATE or a page
split.

PredicateLockPageCombine now retains locks for the page that is being
removed, rather than removing them. This prevents a potentially dangerous
false-positive inconsistency where the local lock table believes that a lock
is held, but it is actually not.

Dan Ports and Kevin Grittner
2011-03-01 19:05:16 +02:00
config Better support for thread-support flag detection with clang 2011-02-16 23:15:54 +02:00
contrib Refactor the executor's API to support data-modifying CTEs better. 2011-02-27 13:44:12 -05:00
doc Update discussion of EXPLAIN to reflect existence of ModifyTable nodes. 2011-03-01 11:37:02 -05:00
src Fix bugs in Serializable Snapshot Isolation. 2011-03-01 19:05:16 +02:00
.gitignore Convert cvsignore to gitignore, and add .gitignore for build targets. 2010-09-22 12:57:04 +02:00
aclocal.m4
configure Add a configure check for Python.h if building with python. 2011-02-26 14:17:57 -05:00
configure.in Add a configure check for Python.h if building with python. 2011-02-26 14:17:57 -05:00
COPYRIGHT Stamp copyrights for year 2011. 2011-01-01 13:18:15 -05:00
GNUmakefile.in Allow make check in PL directories 2011-02-15 06:52:12 +02:00
Makefile Allow make check in PL directories 2011-02-15 06:52:12 +02:00
README Remove useless whitespace at end of lines 2010-11-23 22:34:55 +02:00
README.git

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/.