90c885cdab
Snapshot caching, introduced in 623a9ba79b, did not increment xactCompletionCount during subtransaction abort. That could lead to an older snapshot being reused. That is, at least as far as I can see, not a correctness issue (for MVCC snapshots there's no difference between "in progress" and "aborted"). The only difference between the old and new snapshots would be a newer ->xmax. While HeapTupleSatisfiesMVCC makes the same visibility determination, reusing the old snapshot leads HeapTupleSatisfiesMVCC to not set HEAP_XMIN_INVALID. Which subsequently causes the kill_prior_tuple optimization to not kick in (via HeapTupleIsSurelyDead() returning false). The performance effects of doing the same index-lookups over and over again is how the issue was discovered... Fix the issue by incrementing xactCompletionCount in XidCacheRemoveRunningXids. It already acquires ProcArrayLock exclusively, making that an easy proposition. Add a test to ensure that kill_prior_tuple prevents index growth when it involves aborted subtransaction of the current transaction. Author: Andres Freund Discussion: https://postgr.es/m/20210406043521.lopeo7bbigad3n6t@alap3.anarazel.de Discussion: https://postgr.es/m/20210317055718.v6qs3ltzrformqoa%40alap3.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/.