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gistBuildCallback tried to fetch the size of an index tuple that might have already been freed by gistProcessEmptyingQueue. While this seems to usually be harmless in production builds, in principle it could result in a SIGSEGV, or more likely a bogus value for indtuplesSize leading to poor page-split decisions later in the build. The memory management here is confusing and could stand to be refactored, but for the moment it seems to be enough to fetch the tuple size sooner. AFAICT the indtuples[Size] totals aren't used in between these places; even if they were, the updated values shouldn't be any worse to use. So just move the incrementing of the totals up. It's not very clear why our valgrind-using buildfarm animals haven't noticed this problem, because the relevant code path does seem to be exercised according to the code coverage report. I think the reason that we didn't fix this bug after the first report is that I'd wanted to try to understand that better. However, now that it's been re-discovered let's just be pragmatic and fix it already. Original report by Alexander Lakhin (bug #16329), later rediscovered by Egor Chindyaskin (bug #17874). Patch by Alexander Lakhin (commentary by Pavel Borisov and me). Back-patch to all supported branches. Discussion: https://postgr.es/m/16329-7a6aa9b6fa1118a1@postgresql.org Discussion: https://postgr.es/m/17874-63ca6c7ce42d2103@postgresql.org |
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| README.git | ||
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: https://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 https://www.postgresql.org/download/. For more information look at our web site located at https://www.postgresql.org/.