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is unique and is not referenced above the join. In this case the inner side doesn't affect the query result and can be thrown away entirely. Although perhaps nobody would ever write such a thing by hand, it's a reasonably common case in machine-generated SQL. The current implementation only recognizes the case where the inner side is a simple relation with a unique index matching the query conditions. This is enough for the use-cases that have been shown so far, but we might want to try to handle other cases later. Robert Haas, somewhat rewritten by Tom
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/.