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Commitcfcd57111et al fell over under Valgrind testing. (It seems to be enough to #define USE_VALGRIND, you don't actually need to run it under Valgrind to see failures.) The cause is that remove_rel_from_eclass updates each EquivalenceMember's em_relids, and those can be aliases of the left_relids or right_relids of some RestrictInfo in ec_sources. If the update made em_relids empty then bms_del_member will have pfree'd the relid set, so that the subsequent attempt to clean up ec_sources accesses already-freed memory. We missed seeing ill effects beforecfcd57111because (a) if the pfree happens then we will remove the EquivalenceMember altogether, making the source RestrictInfo no longer of use, and (b) the cleanup of ec_sources didn't touch left/right_relids before that. I'm unclear though on howcfcd57111managed to pass non-USE_VALGRIND testing. Apparently we managed to store another Bitmapset into the freed space before trying to access it, but you'd not think that would happen 100% of the time. I think what USE_VALGRIND changes is that it makes list.c much more memory-hungry, so that the freed space gets claimed by some List node before a Bitmapset can be put there. This failure can be seen in v16, v17, and master, but oddly enough not v18. That's because the SJE patch replaced the simple bms_del_members calls used here with adjust_relid_set, which is careful not to scribble on its input. But commit20efbdffejust recently put back the old coding and thus resurrected the problem. Discussion: https://postgr.es/m/458729.1776724816@sss.pgh.pa.us Backpatch-through: 16, 17, master
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/.