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7505da2f45
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Peter Geoghegan 7505da2f45 Reverse order of newitem nbtree candidate splits. 
Commit fab25024, which taught nbtree to choose candidate split points
more carefully, had _bt_findsplitloc() record all possible split points
in an initial pass over a page that is about to be split.  The order
that candidate split points were processed and stored in was assumed to
match the offset number order of split points on an imaginary version of
the page that contains the same items as the original, but also fits
newitem (the item that provoked the split precisely because it didn't
fit).

However, the order of split points in the final array was not quite what
was expected: the split point that makes newitem the firstright item
came after the split point that makes newitem the lastleft item -- not
before.  As a result, _bt_findsplitloc() could get confused about the
leftmost and rightmost tuples among all possible split points recorded
for the page.  This seems to have no appreciable impact on the quality
of the final split point chosen by _bt_findsplitloc(), but it's still
wrong.

To fix, switch the order in which newitem candidate splits are recorded
in.  This also makes it possible to describe candidate split points in
terms of which pair of adjoining tuples enclose the split point within
_bt_findsplitloc(), making it clearer why it's generally safe for
_bt_split() to expect lastleft and firstright tuples.
2019-05-15 12:22:07 -07:00
config Update config.guess and config.sub 2019-04-27 14:25:00 +02:00
contrib Standardize ItemIdData terminology. 2019-05-13 15:53:39 -07:00
doc docs: properly indent PG 12 release notes 2019-05-15 12:44:59 -04:00
src Reverse order of newitem nbtree candidate splits. 2019-05-15 12:22:07 -07:00
.dir-locals.el Make Emacs perl-mode indent more like perltidy. 2019-01-13 11:32:31 -08:00
.gitattributes doc: Add some images 2019-03-27 23:10:23 +01:00
.gitignore Support for optimizing and emitting code in LLVM JIT provider. 2018-03-22 11:05:22 -07:00
aclocal.m4 Fix configure's AC_CHECK_DECLS tests to work correctly with clang. 2018-11-19 12:01:47 -05:00
configure Reorder configure tests for accept() in Windows 2019-03-04 14:42:12 -05:00
configure.in Fix PERMIT_DECLARATION_AFTER_STATEMENT initialization. 2019-02-16 13:12:28 -08:00
COPYRIGHT Update copyright for 2019 2019-01-02 12:44:25 -05:00
GNUmakefile.in Process EXTRA_INSTALL serially, during the first temp-install. 2018-12-31 13:54:38 -08:00
HISTORY Change documentation references to PG website to use https: not http: 2017-05-20 21:50:47 -04:00
Makefile Fix non-GNU makefiles for AIX make. 2017-11-30 00:57:22 -08:00
README Change documentation references to PG website to use https: not http: 2017-05-20 21:50:47 -04:00
README.git Change documentation references to PG website to use https: not http: 2017-05-20 21:50:47 -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:

	https://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.  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
https://www.postgresql.org/download/.  For more information look at our
web site located at https://www.postgresql.org/.