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Some buildfarm members using CLOBBER_CACHE_ALWAYS have been having OOM problems of late. Commit 2455ab488 addressed this problem by recovering space transiently used within RelationBuildPartitionDesc, but it turns out that leaves quite a lot on the table, because other subroutines of RelationBuildDesc also leak memory like mad. Let's move the temp-context management into RelationBuildDesc so that leakage from the other subroutines is also recovered. I examined this issue by arranging for postgres.c to dump the size of MessageContext just before resetting it in each command cycle, and then running the update.sql regression test (which is one of the two that are seeing buildfarm OOMs) with and without CLOBBER_CACHE_ALWAYS. Before 2455ab488, the peak space usage with CCA was as much as 250MB. That patch got it down to ~80MB, but with this patch it's about 0.5MB, and indeed the space usage now seems nearly indistinguishable from a non-CCA build. RelationBuildDesc's traditional behavior of not worrying about leaking transient data is of many years' standing, so I'm pretty hesitant to change that without more evidence that it'd be useful in a normal build. (So far as I can see, non-CCA memory consumption is about the same with or without this change, whuch if anything suggests that it isn't useful.) Hence, configure the patch so that we recover space only when CLOBBER_CACHE_ALWAYS or CLOBBER_CACHE_RECURSIVELY is defined. However, that choice can be overridden at compile time, in case somebody would like to do some performance testing and try to develop evidence for changing that decision. It's possible that we ought to back-patch this change, but in the absence of back-branch OOM problems in the buildfarm, I'm not in a hurry to do that. Discussion: https://postgr.es/m/CA+TgmoY3bRmGB6-DUnoVy5fJoreiBJ43rwMrQRCdPXuKt4Ykaw@mail.gmail.com
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/.