sql: use AOST -10s when building crdb_internal.table_row_statistics

This commit updates the query used to build the virtual table
crdb_internal.table_row_statistics so that it is always run at AS OF
SYSTEM TIME '-10s'. This will reduce contention on the
system.table_statistics table and avoid delays when running SHOW TABLES,
which queries crdb_internal.table_row_statistics.

Informs #58189

Release note (performance improvement): Updated the query used to build
the virtual table crdb_internal.table_row_statistics so that it is always
run at AS OF SYSTEM TIME '-10s'. This should reduce contention on
the table and improve performance for transactions that rely on
crdb_internal.table_row_statistics, such as SHOW TABLES.

pkg/sql/catalog/descs/collection.go

@@ -309,7 +309,8 @@ func (tc *Collection) getDescriptorFromStore(
 ) (found bool, desc catalog.Descriptor, err error) {
 	// Bypass the namespace lookup from the store for system tables.
 	descID := bootstrap.LookupSystemTableDescriptorID(ctx, tc.settings, tc.codec(), parentID, name)
-	if descID == descpb.InvalidID {
+	isSystemDescriptor := descID != descpb.InvalidID
+	if !isSystemDescriptor {
 		var found bool
 		var err error
 		found, descID, err = catalogkv.LookupObjectID(ctx, txn, codec, parentID, parentSchemaID, name)
@@ -321,6 +322,10 @@ func (tc *Collection) getDescriptorFromStore(
 	desc, err = catalogkv.GetAnyDescriptorByID(ctx, txn, codec, descID, catalogkv.Mutable)
 	if err != nil {
 		return false, nil, err
+	} else if desc == nil && isSystemDescriptor {
+		// This can happen during startup because we're not actually looking up the
+		// system descriptor IDs in KV.
+		return false, nil, errors.Wrapf(catalog.ErrDescriptorNotFound, "descriptor %d not found", descID)
 	} else if desc == nil {
 		// Having done the namespace lookup, the descriptor must exist.
 		return false, nil, errors.AssertionFailedf("descriptor %d not found", descID)

pkg/sql/crdb_internal.go

@@ -409,30 +409,49 @@ CREATE TABLE crdb_internal.tables (
 	},
 }
 
+// statsAsOfTimeClusterMode controls the cluster setting for the duration which
+// is used to define the AS OF time for querying the system.table_statistics
+// table when building crdb_internal.table_row_statistics.
+var statsAsOfTimeClusterMode = settings.RegisterDurationSetting(
+	"sql.crdb_internal.table_row_statistics.as_of_time",
+	"historical query time used to build the crdb_internal.table_row_statistics table",
+	-10*time.Second,
+)
+
 var crdbInternalTablesTableLastStats = virtualSchemaTable{
-	comment: "the latest stats for all tables accessible by current user in current database (KV scan)",
+	comment: "stats for all tables accessible by current user in current database as of 10s ago",
 	schema: `
 CREATE TABLE crdb_internal.table_row_statistics (
   table_id                   INT         NOT NULL,
   table_name                 STRING      NOT NULL,
   estimated_row_count        INT
 )`,
 	populate: func(ctx context.Context, p *planner, db *dbdesc.Immutable, addRow func(...tree.Datum) error) error {
-		// Collect the latests statistics for all tables.
-		query := `
+		// Collect the statistics for all tables AS OF 10 seconds ago to avoid
+		// contention on the stats table. We pass a nil transaction so that the AS
+		// OF clause can be independent of any outer query.
+		query := fmt.Sprintf(`
            SELECT s."tableID", max(s."rowCount")
              FROM system.table_statistics AS s
              JOIN (
                     SELECT "tableID", max("createdAt") AS last_dt
                       FROM system.table_statistics
                      GROUP BY "tableID"
                   ) AS l ON l."tableID" = s."tableID" AND l.last_dt = s."createdAt"
-            GROUP BY s."tableID"`
+            AS OF SYSTEM TIME '%s'
+            GROUP BY s."tableID"`, statsAsOfTimeClusterMode.String(&p.ExecCfg().Settings.SV))
 		statRows, err := p.ExtendedEvalContext().ExecCfg.InternalExecutor.QueryEx(
-			ctx, "crdb-internal-statistics-table", p.txn,
+			ctx, "crdb-internal-statistics-table", nil,
 			sessiondata.InternalExecutorOverride{User: security.RootUserName()},
 			query)
 		if err != nil {
+			// This query is likely to cause errors due to SHOW TABLES being run less
+			// than 10 seconds after cluster startup (10s is the default AS OF time
+			// for the query), causing the error "descriptor not found". We should
+			// tolerate this error and return nil.
+			if errors.Is(err, catalog.ErrDescriptorNotFound) {
+				return nil
+			}
 			return err
 		}
 

pkg/sql/logictest/logic.go

@@ -1577,6 +1577,14 @@ func (t *logicTest) newCluster(serverArgs TestServerArgs) {
 		if _, err := conn.Exec("SET CLUSTER SETTING sql.defaults.interleaved_tables.enabled = true"); err != nil {
 			t.Fatal(err)
 		}
+
+		// Update the default AS OF time for querying the system.table_statistics
+		// table to create the crdb_internal.table_row_statistics table.
+		if _, err := conn.Exec(
+			"SET CLUSTER SETTING sql.crdb_internal.table_row_statistics.as_of_time = '-1µs'",
+		); err != nil {
+			t.Fatal(err)
+		}
 	}
 
 	if cfg.overrideDistSQLMode != "" {

pkg/sql/logictest/testdata/logic_test/event_log

@@ -470,6 +470,7 @@ ORDER BY "timestamp", info
 0  1  {"EventType": "set_cluster_setting", "SettingName": "kv.range_merge.queue_enabled", "Statement": "SET CLUSTER SETTING \"kv.range_merge.queue_enabled\" = false", "User": "root", "Value": "false"}
 0  1  {"EventType": "set_cluster_setting", "PlaceholderValues": ["5"], "SettingName": "sql.stats.automatic_collection.min_stale_rows", "Statement": "SET CLUSTER SETTING \"sql.stats.automatic_collection.min_stale_rows\" = $1::INT8", "User": "root", "Value": "5"}
 0  1  {"EventType": "set_cluster_setting", "SettingName": "sql.defaults.interleaved_tables.enabled", "Statement": "SET CLUSTER SETTING \"sql.defaults.interleaved_tables.enabled\" = true", "User": "root", "Value": "true"}
+0  1  {"EventType": "set_cluster_setting", "SettingName": "sql.crdb_internal.table_row_statistics.as_of_time", "Statement": "SET CLUSTER SETTING \"sql.crdb_internal.table_row_statistics.as_of_time\" = e'-1\\u00B5s'", "User": "root", "Value": "-00:00:00.000001"}
 0  1  {"EventType": "set_cluster_setting", "SettingName": "kv.allocator.load_based_lease_rebalancing.enabled", "Statement": "SET CLUSTER SETTING \"kv.allocator.load_based_lease_rebalancing.enabled\" = false", "User": "root", "Value": "false"}
 0  1  {"EventType": "set_cluster_setting", "SettingName": "kv.allocator.load_based_lease_rebalancing.enabled", "Statement": "SET CLUSTER SETTING \"kv.allocator.load_based_lease_rebalancing.enabled\" = DEFAULT", "User": "root", "Value": "DEFAULT"}
 0  1  {"EventType": "set_cluster_setting", "PlaceholderValues": ["'some string'"], "SettingName": "cluster.organization", "Statement": "SET CLUSTER SETTING \"cluster.organization\" = $1", "User": "root", "Value": "'some string'"}