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We have to be sure that we have revalidated each nailed-in-cache relcache entry before we try to use it to load data for some other relcache entry. The introduction of "mapped relations" in 9.0 broke this, because although we updated the state kept in relmapper.c early enough, we failed to propagate that information into relcache entries soon enough; in particular, we could try to fetch pg_class rows out of pg_class before we'd updated its relcache entry's rd_node.relNode value from the map. This bug accounts for Dave Gould's report of failures after "vacuum full pg_class", and I believe that there is risk for other system catalogs as well. The core part of the fix is to copy relmapper data into the relcache entries during "phase 1" in RelationCacheInvalidate(), before they'll be used in "phase 2". To try to future-proof the code against other similar bugs, I also rearranged the order in which nailed relations are visited during phase 2: now it's pg_class first, then pg_class_oid_index, then other nailed relations. This should ensure that RelationClearRelation can apply RelationReloadIndexInfo to all nailed indexes without risking use of not-yet-revalidated relcache entries. Back-patch to 9.0 where the relation mapper was introduced. |
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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/.