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We may process relcache flush requests during transaction startup or shutdown. In general it's not terribly safe to do catalog access at those times, so the code's habit of trying to immediately revalidate unflushable relcache entries is risky. Although there are no field trouble reports that are positively traceable to this, we have been able to demonstrate failure of the assertions recently added in RelationIdGetRelation() and SearchCatCache(). On the other hand, it seems safe to just postpone revalidation of the cache entry until we're inside a valid transaction. The one case where this is questionable is where we're exiting a subtransaction and the outer transaction is holding the relcache entry open --- but if we made any significant changes to the rel inside such a subtransaction, we've got problems anyway. There are mechanisms in place to prevent that (to wit, locks for cross-session cases and CheckTableNotInUse() for intra-session cases), so let's trust to those mechanisms to keep us out of trouble.
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/.