d5e96520ff
9bdb300de modified the EXPLAIN output for Hash Aggregate to show details from parallel workers. However, it neglected to consider that a given parallel worker may not have assisted with the given Hash Aggregate. This can occur when workers fail to start or during Parallel Append with enable_partitionwise_join enabled when only a single worker is working on a non-parallel aware sub-plan. It could also happen if a worker simply wasn't fast enough to get any work done before other processes went and finished all the work. The bogus output came from the fact that ExplainOpenWorker() skipped showing any details for non-initialized workers but show_hashagg_info() did show details from the worker. This meant that the worker properties that were shown were not properly attributed to the worker that they belong to. In passing, we also now don't show Hash Aggregate properties for the leader process when it did not contribute any work to the Hash Aggregate. This can occur either during Parallel Append when only a parallel worker worked on a given sub plan or with parallel_leader_participation set to off. This aims to make the behavior of Hash Aggregate's EXPLAIN output more similar to Sort's. Reported-by: Justin Pryzby Discussion: https://postgr.es/m/20200805012105.GZ28072%40telsasoft.com Backpatch-through: 13, where the original breakage was introduced
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/.