57664ed25e
Add PlaceHolderVar wrappers as needed to make UNION ALL sub-select output expressions appear non-constant and distinct from each other. This makes the world safe for add_child_rel_equivalences to do what it does. Before, it was possible for that function to add identical expressions to different EquivalenceClasses, which logically should imply merging such ECs, which would be wrong; or to improperly add a constant to an EquivalenceClass, drastically changing its behavior. Per report from Teodor Sigaev. The only currently known consequence of this bug is "MergeAppend child's targetlist doesn't match MergeAppend" planner failures in 9.1 and later. I am suspicious that there may be other failure modes that could affect older release branches; but in the absence of any hard evidence, I'll refrain from back-patching further than 9.1.
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/.