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MIN/MAX not be converted to use an index if the query WHERE clause contains any volatile functions or subplans. I had originally feared that the conversion might alter the behavior of such a query with respect to a volatile function. Well, so it might, but only in the sense that the function would get evaluated at a subset of the table rows rather than all of them --- and we have never made any such guarantee anyway. (For instance, we don't refuse to use an index for an ordinary non-aggregate query when one of the non-indexable filter conditions contains a volatile function.) The prohibition against subplans was because of worry that that case wasn't adequately tested, which it wasn't, but it turns out to be possible to make 8.1 fail anyway: regression=# select o.ten, (select max(unique2) from tenk1 i where ten = o.ten or ten = (select f1 from int4_tbl limit 1)) from tenk1 o; ERROR: direct correlated subquery unsupported as initplan This is due to bogus code in SS_make_initplan_from_plan (it's an initplan, ergo it can't have any parParams). Having fixed that, we might as well allow subplans as well as initplans. |
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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/.