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This commit adds the infrastructure for more detailed IO statistics. The calls to actually count IOs, a system view to access the new statistics, documentation and tests will be added in subsequent commits, to make review easier. While we already had some IO statistics, e.g. in pg_stat_bgwriter and pg_stat_database, they did not provide sufficient detail to understand what the main sources of IO are, or whether configuration changes could avoid IO. E.g., pg_stat_bgwriter.buffers_backend does contain the number of buffers written out by a backend, but as that includes extending relations (always done by backends) and writes triggered by the use of buffer access strategies, it cannot easily be used to tune background writer or checkpointer. Similarly, pg_stat_database.blks_read cannot easily be used to tune shared_buffers / compute a cache hit ratio, as the use of buffer access strategies will often prevent a large fraction of the read blocks to end up in shared_buffers. The new IO statistics count IO operations (evict, extend, fsync, read, reuse, and write), and are aggregated for each combination of backend type (backend, autovacuum worker, bgwriter, etc), target object of the IO (relations, temp relations) and context of the IO (normal, vacuum, bulkread, bulkwrite). What is tracked in this series of patches, is sufficient to perform the aforementioned analyses. Further details, e.g. tracking the number of buffer hits, would make that even easier, but was left out for now, to keep the scope of the already large patchset manageable. Bumps PGSTAT_FILE_FORMAT_ID. Author: Melanie Plageman <melanieplageman@gmail.com> Reviewed-by: Andres Freund <andres@anarazel.de> Reviewed-by: Justin Pryzby <pryzby@telsasoft.com> Reviewed-by: Kyotaro Horiguchi <horikyota.ntt@gmail.com> Discussion: https://postgr.es/m/20200124195226.lth52iydq2n2uilq@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/.