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We must set the visibility map bit before releasing our exclusive lock on the heap page; otherwise, someone might clear the heap page bit before we set the visibility map bit, leading to a situation where the visibility map thinks the page is all-visible but it's really not. This problem has existed since 8.4, but it wasn't critical before we had index-only scans, since the worst case scenario was that the page wouldn't get vacuumed until the next scan_all vacuum. Along the way, a couple of minor, related improvements: (1) if we pause the heap scan to do an index vac cycle, release any visibility map page we're holding, since really long-running pins are not good for a variety of reasons; and (2) warn if we see a page that's marked all-visible in the visibility map but not on the page level, since that should never happen any more (it was allowed in previous releases, but not in 9.2).
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/.