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ec94bc1473
One of the changes I made in commit 8703059c6b55c427 turns out not to have been such a good idea: we still need the exception in join_is_legal() that allows a join if both inputs already overlap the RHS of the special join we're checking. Otherwise we can miss valid plans, and might indeed fail to find a plan at all, as in recent report from Andreas Seltenreich. That code was added way back in commit c17117649b9ae23d, but I failed to include a regression test case then; my bad. Put it back with a better explanation, and a test this time. The logic does end up a bit different than before though: I now believe it's appropriate to make this check first, thereby allowing such a case whether or not we'd consider the previous SJ(s) to commute with this one. (Presumably, we already decided they did; but it was confusing to have this consideration in the middle of the code that was handling the other case.) Back-patch to all active branches, like the previous 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, 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/.