a2e092e1c7
threshold for tuple length. On 4-byte-MAXALIGN machines, the toast code creates tuples that have t_len exactly TOAST_TUPLE_THRESHOLD ... but this number is not itself maxaligned, so if heap_insert maxaligns t_len before comparing to TOAST_TUPLE_THRESHOLD, it'll uselessly recurse back to tuptoaster.c, wasting cycles. (It turns out that this does not happen on 8-byte-MAXALIGN machines, because for them the outer MAXALIGN in the TOAST_MAX_CHUNK_SIZE macro reduces TOAST_MAX_CHUNK_SIZE so that toast tuples will be less than TOAST_TUPLE_THRESHOLD in size. That MAXALIGN is really incorrect, but we can't remove it now, see below.) There isn't any particular value in maxaligning before comparing to the thresholds, so just don't do that, which saves a small number of cycles in itself. These numbers should be rejiggered to minimize wasted space on toast-relation pages, but we can't do that in the back branches because changing TOAST_MAX_CHUNK_SIZE would force an initdb (by changing the contents of toast tables). We can move the toast decision thresholds a bit, though, which is what this patch effectively does. Thanks to Pavan Deolasee for discovering the unintended recursion. Back-patch into 8.2, but not further, pending more testing. (HEAD is about to get a further patch modifying the thresholds, so it won't help much for testing this form of the patch.)
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/pgSQL - included in PostgreSQL source distribution PL/Perl - included in PostgreSQL source distribution PL/PHP - http://projects.commandprompt.com/projects/public/plphp PL/Python - included in PostgreSQL source distribution PL/Java - http://gborg.postgresql.org/project/pljava/projdisplay.php PL/Tcl - included in PostgreSQL source distribution 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/.