Fixes cockroachdb#40989 Previously, there was no way to enable or disable automatic statistics collection at the table level. It could only be turned on or off via the `sql.stats.automatic_collection.enabled` cluster setting. This was inadequate because statistics collection can be expensive for large tables, and it would be desirable to defer collection until after data is finished loading, or in off hours. Also, small tables which are frequently updated may trigger statistics collection leading to unnecessary overhead and/or unpredictable query plan changes. To address this, this patch adds support for setting of the following cluster settings at the table level: ``` sql_stats_automatic_collection_enabled sql_stats_automatic_collection_min_stale_rows sql_stats_automatic_collection_fraction_stale_rows ``` which correspond to the similarly-named cluster settings: ``` sql.stats.automatic_collection.enabled sql.stats.automatic_collection.min_stale_rows sql.stats.automatic_collection.fraction_stale_rows ``` for example: ``` ALTER TABLE t1 SET (sql_stats_automatic_collection_enabled = true); ALTER TABLE t1 SET (sql_stats_automatic_collection_fraction_stale_rows = 0.1, sql_stats_automatic_collection_min_stale_rows = 2000); ``` The table-level setting takes precedence over the cluster setting. Release justification: Low risk fix for missing fine-grained control over automatic statistics collection. Release note (sql change): Automatic statistics collection can now be enabled or disabled for individual tables, taking precedence over the cluster setting, for example: ``` ALTER TABLE t1 SET (sql_stats_automatic_collection_enabled = true); ALTER TABLE t1 SET (sql_stats_automatic_collection_enabled = false); ALTER TABLE t1 RESET (sql_stats_automatic_collection_enabled); ``` RESET removes the setting value entirely, in which case the similarly-name cluster setting, `sql.stats.automatic_collection.enabled`, is in effect for the table. Cluster settings `sql.stats.automatic_collection.fraction_stale_rows` and `sql.stats.automatic_collection.min_stale_rows` now also have table setting counterparts: ``` sql_stats_automatic_collection_fraction_stale_rows sql_stats_automatic_collection_min_stale_rows ``` The table settings may be set at table creation time, or later via ALTER TABLE ... SET, independent of whether auto stats is enabled: ``` ALTER TABLE t1 SET (sql_stats_automatic_collection_fraction_stale_rows = 0.1, sql_stats_automatic_collection_min_stale_rows = 2000); CREATE TABLE t1 (a INT, b INT) WITH (sql_stats_automatic_collection_enabled = true, sql_stats_automatic_collection_min_stale_rows = 1000000, sql_stats_automatic_collection_fraction_stale_rows= 0.05 ); ``` The current table settings (storage parameters) are shown in the `WITH` clause output of `SHOW CREATE TABLE`. Note, any row mutations which have occurred a minute or two before disabling auto stats collection via `ALTER TABLE ... SET` may trigger stats collection, though DML submitted after the setting change will not.

Commits

Commits on May 3, 2022

stats: table setting to turn auto stats collection on/off