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This patch improves performance of most built-in aggregates that formerly used a NUMERIC or NUMERIC array as their transition type; this includes not only aggregates on numeric inputs, but some aggregates on integer inputs where overflow of an int8 value is a possibility. The code now uses a special-purpose data structure to avoid array construction and deconstruction overhead, as well as packing and unpacking overhead for numeric values. These aggregates' transition type is now declared as INTERNAL, since it doesn't correspond to any SQL data type. To keep the planner from thinking that that means a lot of storage will be used, we make use of the just-added pg_aggregate.aggtransspace feature. The space estimate is set to 128 bytes, which is at least in the right ballpark. Hadi Moshayedi, reviewed by Pavel Stehule and Tomas Vondra
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/.