ccc4c07499
In some corner cases, it is possible for the BRIN index relation to be extended by brin_getinsertbuffer but the new page not be used immediately for anything by its callers; when this happens, the page is initialized and the FSM is updated (by brin_getinsertbuffer) with the info about that page, but these actions are not WAL-logged. A later index insert/update can use the page, but since the page is already initialized, the initialization itself is not WAL-logged then either. Replay of this sequence of events causes recovery to fail altogether. There is a related corner case within brin_getinsertbuffer itself, in which we extend the relation to put a new index tuple there, but later find out that we cannot do so, and do not return the buffer; the page obtained from extension is not even initialized. The resulting page is lost forever. To fix, shuffle the code so that initialization is not the responsibility of brin_getinsertbuffer anymore, in normal cases; instead, the initialization is done by its callers (brin_doinsert and brin_doupdate) once they're certain that the page is going to be used. When either those functions determine that the new page cannot be used, before bailing out they initialize the page as an empty regular page, enter it in FSM and WAL-log all this. This way, the page is usable for future index insertions, and WAL replay doesn't find trying to insert tuples in pages whose initialization didn't make it to the WAL. The same strategy is used in brin_getinsertbuffer when it cannot return the new page. Additionally, add a new step to vacuuming so that all pages of the index are scanned; whenever an uninitialized page is found, it is initialized as empty and WAL-logged. This closes the hole that the relation is extended but the system crashes before anything is WAL-logged about it. We also take this opportunity to update the FSM, in case it has gotten out of date. Thanks to Heikki Linnakangas for finding the problem that kicked some additional analysis of BRIN page assignment code. Backpatch to 9.5, where BRIN was introduced. Discussion: https://www.postgresql.org/message-id/20150723204810.GY5596@postgresql.org |
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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. 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/.