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This fixes a bug in the edge case where, for a temp table, heap_page_prune() can end up with a different horizon than heap_vacuum_rel(). Which can trigger errors like "ERROR: cannot freeze committed xmax ...". The bug was introduced due to interaction of a7212be8b9e "Set cutoff xmin more aggressively when vacuuming a temporary table." with dc7420c2c92 "snapshot scalability: Don't compute global horizons while building snapshots.". The problem is caused by lazy_scan_heap() assuming that the only reason its HeapTupleSatisfiesVacuum() call would return HEAPTUPLE_DEAD is if the tuple is a HOT tuple, or if the tuple's inserting transaction has aborted since the heap_page_prune() call. But after a7212be8b9e that was also possible in other cases for temp tables, because heap_page_prune() uses a different visibility test after dc7420c2c92. The fix is fairly simple: Move the special case logic for temp tables from vacuum_set_xid_limits() to the infrastructure introduced in dc7420c2c92. That ensures that the horizon used for pruning is at least as aggressive as the one used by lazy_scan_heap(). The concrete horizon used for temp tables is slightly different than the logic in dc7420c2c92, but should always be as aggressive as before (see comments). A significant benefit to centralizing the logic procarray.c is that now the more aggressive horizons for temp tables does not just apply to VACUUM but also to e.g. HOT pruning and the nbtree killtuples logic. Because isTopLevel is not needed by vacuum_set_xid_limits() anymore, I undid the the related changes from a7212be8b9e. This commit also adds an isolation test ensuring that the more aggressive vacuuming and pruning of temp tables keeps working. Debugged-By: Amit Kapila <amit.kapila16@gmail.com> Debugged-By: Tom Lane <tgl@sss.pgh.pa.us> Debugged-By: Ashutosh Sharma <ashu.coek88@gmail.com> Author: Andres Freund <andres@anarazel.de> Discussion: https://postgr.es/m/20201014203103.72oke6hqywcyhx7s@alap3.anarazel.de Discussion: https://postgr.es/m/20201015083735.derdzysdtqdvxshp@alap3.anarazel.de
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/.