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Presently, parallel restores spend a lot of time sorting this list so that we pick the largest items first. With many tables, this sorting can become a significant bottleneck. There are a couple of reports from the field about this, and it is easy to reproduce. This commit improves the performance of parallel pg_restore with many tables by converting its ready_list to a priority queue, i.e., a binary heap. We will first try to run the highest priority item, but if it cannot be chosen due to the lock heuristic, we'll do a sequential scan through the heap nodes until we find one that is runnable. This means that we might end up picking an item with a much lower priority. However, we expect that we will typically be able to pick one of the first few items, which should usually have a relatively high priority. Suggested-by: Tom Lane Tested-by: Pierre Ducroquet Reviewed-by: Tom Lane Discussion: https://postgr.es/m/3612876.1689443232%40sss.pgh.pa.us
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/.