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We're seeing occasional instability in the plans generated for parallel queries on the "a_star" table hierarchy. This suggests that something is changing the planner's stats for those tables, but that should not be happening within a regression test run. To try to gather some information about what's happening, insert additional queries to check the basic page/tuple counts for these tables, as well as whether any vacuums or analyzes have happened on them. (We expect that only the database-wide VACUUM in sanity_check.sql will have touched them.) I added the probes not only in select_parallel.sql itself, but also in stats.sql, bearing in mind that the stats collector's lag may prevent the initial query from reporting current truth. If any extra vacuum/analyze has happened, the recheck in stats.sql definitely ought to see it. This commit can be reverted once we figure out what's going on. Per suggestion from David Rowley, though I changed the queries around. Discussion: https://postgr.es/m/CA+hUKG+0CxrKRWRMf5ymN3gm+BECHna2B-q1w8onKBep4HasUw@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/.