520bcd9c9b
If we find a DELETE_IN_PROGRESS HOT-updated tuple, it is impossible to know whether to index it or not except by waiting to see if the deleting transaction commits. If it doesn't, the tuple might again be LIVE, meaning we have to index it. So wait and recheck in that case. Also, we must not rely on ii_BrokenHotChain to decide that it's possible to omit tuples from the index. That could result in omitting tuples that we need, particularly in view of yesterday's fixes to not necessarily set indcheckxmin (but it's broken even without that, as per my analysis today). Since this is just an extremely marginal performance optimization, dropping the test shouldn't hurt. These cases are only expected to happen in system catalogs (they're possible there due to early release of RowExclusiveLock in most catalog-update code paths). Since reindexing of a system catalog isn't a particularly performance-critical operation anyway, there's no real need to be concerned about possible performance degradation from these changes. The worst aspects of this bug were introduced in 9.0 --- 8.x will always wait out a DELETE_IN_PROGRESS tuple. But I think dropping index entries on the strength of ii_BrokenHotChain is dangerous even without that, so back-patch removal of that optimization to 8.3 and 8.4. |
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README
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/.