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though it is an inner rather than outer join type. This essentially means that we don't bother to separate "pushed down" qual conditions from actual join quals at a semijoin plan node; which is okay because the restrictions of SQL syntax make it impossible to have a pushed-down qual that references the inner side of a semijoin. This allows noticeably better optimization of IN/EXISTS cases than we had before, since the equivalence-class machinery can now use those quals. Also fix a couple of other mistakes that had essentially disabled the ability to unique-ify the inner relation and then join it to just a subset of the left-hand relations. An example case using the regression database is select * from tenk1 a, tenk1 b where (a.unique1,b.unique2) in (select unique1,unique2 from tenk1 c); which is planned reasonably well by 8.3 and earlier but had been forcing a cartesian join of a/b in CVS HEAD. |
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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/.