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031cc55bbe
The pglz compressor has a significant startup cost, because it has to initialize to zeros the history-tracking hash table. On a 64-bit system, the hash table was 64kB in size. While clearing memory is pretty fast, for very short inputs the relative cost of that was quite large. This patch alleviates that in two ways. First, instead of storing pointers in the hash table, store 16-bit indexes into the hist_entries array. That slashes the size of the hash table to 1/2 or 1/4 of the original, depending on the pointer width. Secondly, adjust the size of the hash table based on input size. For very small inputs, you don't need a large hash table to avoid collisions. Review by Amit Kapila. |
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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/.