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When we are doing GEQO join planning, the current memory context is a short-lived context that will be reset at the end of geqo_eval(). However, the RelOptInfos for base relations are set up before that and then re-used across many GEQO cycles. Hence, any code that modifies a baserel during join planning has to be careful not to put pointers to the short-lived context into the baserel struct. mark_dummy_rel got this wrong, leading to easy-to-reproduce-once-you-know-how crashes in 8.4, as reported off-list by Leo Carson of SDSC. Some improvements made in 9.0 make it difficult to demonstrate the crash in 9.0 or HEAD; but there's no doubt that there's still a risk factor here, so patch all branches that have the function. (Note: 8.3 has a similar function, but it's only applied to joinrels and thus is not a hazard.)
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/.