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Commit 09cb5c0e7d6fbc9dee26dc429e4fc0f2a88e5272 added a similar optimization to btree back in 2006, but nobody bothered to implement the same thing for hash indexes, probably because they weren't WAL-logged and had lots of other performance problems as well. As with the corresponding btree case, this eliminates the problem of potentially needing to refind our position within the page, and cuts down on pin/unpin traffic as well. Ashutosh Sharma, reviewed by Alexander Korotkov, Jesper Pedersen, Amit Kapila, and me. Some final edits to comments and README by me. Discussion: http://postgr.es/m/CAE9k0Pm3KTx93K8_5j6VMzG4h5F+SyknxUwXrN-zqSZ9X8ZS3w@mail.gmail.com
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/.