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Andres Freund fc4b3dea29 User narrower representative tuples in the hash-agg hashtable. 
So far the hashtable stored representative tuples in the form of its
input slot, with all columns in the hashtable that are not
needed (i.e. not grouped upon or functionally dependent) set to NULL.

Thats good for saving memory, but it turns out that having tuples full
of NULL isn't free. slot_deform_tuple is faster if there's no NULL
bitmap even if no NULLs are encountered, and skipping over leading NULLs
isn't free.

So compute a separate tuple descriptor that only contains the needed
columns. As columns have already been moved in/out the slot for the
hashtable that does not imply additional per-row overhead.

Author: Andres Freund
Reviewed-By: Heikki Linnakangas
Discussion: https://postgr.es/m/20161103110721.h5i5t5saxfk5eeik@alap3.anarazel.de
 		2016-11-30 17:30:09 -08:00
config Fix python shlib probe for Cygwin. 2016-10-07 11:27:34 -04:00
contrib Remove dead stuff from pgcrypto. 2016-11-30 13:04:16 +02:00
doc Doc: improve description of trim() and related functions. 2016-11-30 13:34:13 -05:00
src User narrower representative tuples in the hash-agg hashtable. 2016-11-30 17:30:09 -08:00
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COPYRIGHT Update copyright for 2016 2016-01-02 13:33:40 -05:00
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HISTORY Improve text of stub HISTORY file. 2014-02-12 18:16:17 -05:00
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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.  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/.