b62f94c603
The locution "EXISTS(SELECT ... LIMIT 1)" seems to be rather common among people who don't realize that the database already performs optimizations equivalent to putting LIMIT 1 in the sub-select. Unfortunately, this was actually making things worse, because it prevented us from optimizing such EXISTS clauses into semi or anti joins. Teach simplify_EXISTS_query() to suppress constant-positive LIMIT clauses. That fixes the semi/anti-join case, and may help marginally even for cases that have to be left as sub-SELECTs. Marti Raudsepp, reviewed by David Rowley
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. 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/.