These parameters control server-wide statistics collection features.
      When statistics collection is enabled, the data that is produced 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 the time when
        that command began execution. This parameter is on by
        default. Note that even when enabled, this information is not
        visible to all users, only 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 can change this setting.
       
track_activity_query_size (integer)
      
      
       Specifies the number of bytes reserved to track the currently
       executing command for each active session, for the
       pg_stat_activity.query field.
       The default value is 1024. 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 can change this setting.
track_io_timing (boolean)
      
      
        Enables timing of database I/O calls.  This parameter is off by
        default, because 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, and by pg_stat_statements.  Only superusers 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 can change this setting.
       
SQL-language functions that are simple enough to be “inlined” into the calling query will not be tracked, regardless of this setting.
stats_temp_directory (string)
      
      
        Sets the directory to store temporary statistics data in. This can be
        a path relative to the data directory or an absolute path. The default
        is pg_stat_tmp. Pointing this at a RAM-based
        file system will decrease physical I/O requirements and can lead to
        improved performance.
        This parameter can only be set in the postgresql.conf
        file or on the server command line.
       
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 can change these settings.