5ead85fbc8
Expose the count of index searches/index descents in EXPLAIN ANALYZE's output for index scan nodes. This information is particularly useful with scans that use ScalarArrayOp quals, where the number of index scans isn't predictable in advance (at least not with optimizations like the one added to nbtree by Postgres 17 commit 5bf748b8). It will also be useful when EXPLAIN ANALYZE shows details of an nbtree index scan that uses skip scan optimizations set to be introduced by an upcoming patch. The instrumentation works by teaching index AMs to increment a new nsearches counter whenever a new index search begins. The counter is incremented at exactly the same point that index AMs must already increment the index's pg_stat_*_indexes.idx_scan counter (we're counting the same event, but at the scan level rather than the relation level). The new counter is stored in the scan descriptor (IndexScanDescData), which explain.c reaches by going through the scan node's PlanState. This approach doesn't match the approach used when tracking other index scan specific costs (e.g., "Rows Removed by Filter:"). It is similar to the approach used in other cases where we must track costs that are only readily accessible inside an access method, and not from the executor (e.g., "Heap Blocks:" output for a Bitmap Heap Scan). It is inherently necessary to maintain a counter that can be incremented multiple times during a single amgettuple call (or amgetbitmap call), and directly exposing PlanState.instrument to index access methods seems unappealing. Author: Peter Geoghegan <pg@bowt.ie> Reviewed-By: Tomas Vondra <tomas@vondra.me> Reviewed-By: Robert Haas <robertmhaas@gmail.com> Reviewed-By: Masahiro Ikeda <ikedamsh@oss.nttdata.com> Reviewed-By: Matthias van de Meent <boekewurm+postgres@gmail.com> Discussion: https://postgr.es/m/CAH2-Wz=PKR6rB7qbx+Vnd7eqeB5VTcrW=iJvAsTsKbdG+kW_UA@mail.gmail.com Discussion: https://postgr.es/m/CAH2-WzkRqvaqR2CTNqTZP0z6FuL4-3ED6eQB0yx38XBNj1v-4Q@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.
Copyright and license information can be found in the file COPYRIGHT.
General documentation about this version of PostgreSQL can be found at https://www.postgresql.org/docs/devel/. In particular, information about building PostgreSQL from the source code can be found at https://www.postgresql.org/docs/devel/installation.html.
The latest version of this software, and related software, may be obtained at https://www.postgresql.org/download/. For more information look at our web site located at https://www.postgresql.org/.