20.9. Run-time Statistics

20.9. Run-time Statistics
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20.9.1. Cumulative Query and Index Statistics
20.9.2. Statistics Monitoring

20.9.1. Cumulative Query and Index Statistics

+ These parameters control the server-wide cumulative statistics system. + When enabled, the data that is collected can be accessed via the + pg_stat and pg_statio + family of system views. Refer to Chapter 28 for more + information. +

track_activities (boolean) + +: + Enables the collection of information on the currently + executing command of each session, along with its identifier and the + time when that command began execution. This parameter is on by + default. Note that even when enabled, this information is only + visible to superusers, roles with privileges of the + pg_read_all_stats role and the user owning the + sessions being reported on (including sessions belonging to a role they + have the privileges of), so it should not represent a security risk. + Only superusers and users with the appropriate SET + privilege can change this setting. +
track_activity_query_size (integer) + +: + Specifies the amount of memory reserved to store the text of the + currently executing command for each active session, for the + pg_stat_activity.query field. + If this value is specified without units, it is taken as bytes. + The default value is 1024 bytes. + This parameter can only be set at server start. +
track_counts (boolean) + +: + Enables collection of statistics on database activity. + This parameter is on by default, because the autovacuum + daemon needs the collected information. + Only superusers and users with the appropriate SET + privilege can change this setting. +
track_io_timing (boolean) + +: + Enables timing of database I/O calls. This parameter is off by + default, as it will repeatedly query the operating system for + the current time, which may cause significant overhead on some + platforms. You can use the pg_test_timing tool to + measure the overhead of timing on your system. + I/O timing information is + displayed in + pg_stat_database, in the output of + EXPLAIN when the BUFFERS option + is used, in the output of VACUUM when + the VERBOSE option is used, by autovacuum + for auto-vacuums and auto-analyzes, when log_autovacuum_min_duration is set and by + pg_stat_statements. + Only superusers and users with the appropriate SET + privilege can change this setting. +
track_wal_io_timing (boolean) + +: + Enables timing of WAL I/O calls. This parameter is off by default, + as it will repeatedly query the operating system for the current time, + which may cause significant overhead on some platforms. + You can use the pg_test_timing tool to + measure the overhead of timing on your system. + I/O timing information is + displayed in + pg_stat_wal. + Only superusers and users with the appropriate SET + privilege can change this setting. +
track_functions (enum) + +: + Enables tracking of function call counts and time used. Specify + pl to track only procedural-language functions, + all to also track SQL and C language functions. + The default is none, which disables function + statistics tracking. + Only superusers and users with the appropriate SET + privilege can change this setting. +
Note
+ SQL-language functions that are simple enough to be “inlined” + into the calling query will not be tracked, regardless of this + setting. +
stats_fetch_consistency (enum) + +: + Determines the behavior when cumulative statistics are accessed + multiple times within a transaction. When set to + none, each access re-fetches counters from shared + memory. When set to cache, the first access to + statistics for an object caches those statistics until the end of the + transaction unless pg_stat_clear_snapshot() is + called. When set to snapshot, the first statistics + access caches all statistics accessible in the current database, until + the end of the transaction unless + pg_stat_clear_snapshot() is called. Changing this + parameter in a transaction discards the statistics snapshot. + The default is cache. +
Note
+ none is most suitable for monitoring systems. If + values are only accessed once, it is the most + efficient. cache ensures repeat accesses yield the + same values, which is important for queries involving + e.g. self-joins. snapshot can be useful when + interactively inspecting statistics, but has higher overhead, + particularly if many database objects exist. +

20.9.2. Statistics Monitoring

compute_query_id (enum) + +: + Enables in-core computation of a query identifier. + Query identifiers can be displayed in the pg_stat_activity + view, using EXPLAIN, or emitted in the log if + configured via the log_line_prefix parameter. + The pg_stat_statements extension also requires a query + identifier to be computed. Note that an external module can + alternatively be used if the in-core query identifier computation + method is not acceptable. In this case, in-core computation + must be always disabled. + Valid values are off (always disabled), + on (always enabled), auto, + which lets modules such as pg_stat_statements + automatically enable it, and regress which + has the same effect as auto, except that the + query identifier is not shown in the EXPLAIN output + in order to facilitate automated regression testing. + The default is auto. +
Note
+ To ensure that only one query identifier is calculated and + displayed, extensions that calculate query identifiers should + throw an error if a query identifier has already been computed. +
log_statement_stats (boolean) + + log_parser_stats (boolean) + + log_planner_stats (boolean) + + log_executor_stats (boolean) + +: + For each query, output performance statistics of the respective + module to the server log. This is a crude profiling + instrument, similar to the Unix getrusage() operating + system facility. log_statement_stats reports total + statement statistics, while the others report per-module statistics. + log_statement_stats cannot be enabled together with + any of the per-module options. All of these options are disabled by + default. + Only superusers and users with the appropriate SET + privilege can change these settings. +

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20.8. Error Reporting and Logging	Home	20.10. Automatic Vacuuming

20.9. Run-time Statistics

20.9.1. Cumulative Query and Index Statistics

Note

Note

20.9.2. Statistics Monitoring

Note