Runtime Rule Examples ​

Runtime rules take actions during actual query execution on the workers. These rules are evaluated only for queries with a duration of at least 5 seconds and are evaluated repetitively at 5-second intervals after queries enter the run state.

Set Priority to Critical for Queries Against Specific Tables ​

The following runtime rule makes sure that CPU resources are available to queries against tables that contain matchstats in their names. The rule action sets the priority of these queries to critical:

Rule Preview:
if (w.referencedTables.contains('matchstats') &&
   w.priority === 'low' ||
   w.priority === 'normal' ||
   w.priority === 'high') {
	w.priority = 'critical';
}

Note that if only one query is running on the system, it could be allocated 100% of the available CPU, regardless of its priority. Setting the priority only has an effect when concurrent queries are running.

Log an INFO Message for Large DELETE Queries ​

The following runtime rule, runtime_log_info_msg, logs an INFO message when more than 1 million rows are deleted from any table:

Rule Preview:
if (w.stats.rowsDeleted > 1000000) {
	log.info('More than 1 million rows deleted');
}

The ybsql user sees, for example:

premdb=> delete from newmatchstats where seasonid=7;
DELETE 849801600

The DELETE succeeded, but an INFO message is logged as expected:

More than 1 million rows deleted

Note that runtime rules are processed at 5-second intervals.

Do Not Store Stats for a Database ​

The following runtime rule, runtime_no_stats_for_premdb, turns off statistics logging for queries against the premdb database. This means that sys.log_query will not have a record of these queries.

Rule Preview:
if (w.database === 'premdb') {
	w.statsStored = false;
	log.info('No stats for a premdb query!');
}