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performance issue during regular merge passes not only the 'final merge' case. The original design contemplated that there would never be more than about one free block per 'tape', hence no need for an efficient method of keeping the free blocks sorted. But given the later addition of merge preread behavior in tuplesort.c, there is likely to be about work_mem worth of free blocks, which is not so small ... and for that matter the number of tapes isn't necessarily small anymore either. So we'd better get rid of the assumption entirely. Instead, I'm assuming that the usage pattern will involve alternation between merge preread and writing of a new run. This makes it reasonable to just add blocks to the list without sorting during successive ltsReleaseBlock calls, and then do a qsort() when we start getting ltsGetFreeBlock() calls. Experimentation seems to confirm that there aren't many qsort calls relative to the number of ltsReleaseBlock/ltsGetFreeBlock calls. |
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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 including some of the more common listed below: C++ - http://thaiopensource.org/development/libpqxx/ JDBC - http://jdbc.postgresql.org ODBC - http://odbc.postgresql.org Perl - http://search.cpan.org/~dbdpg/ PHP - http://www.php.net Python - http://www.initd.org/ Ruby - http://ruby.scripting.ca/postgres/ Other language binding are available from a variety of contributing parties. PostgreSQL also has a great number of procedural languages available, a short but not complete list is below: pl/c - Included in PostgreSQL core plPgsql - Included in PostgreSQL core - Similar to Oracle PL/sql plPerl - Included in PostgreSQL core plPHP - http://projects.commandprompt.com/projects/public/plphp plPython - Included in PostgreSQL core plJava - http://gborg.postgresql.org/project/pljava/projdisplay.php plTcl - Included in PostgreSQL core 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/.