sql: set always_distribute_full_scans for internal validation queries

The validation queries we run after a backfill all use full table scans,
and usually there are no stats available. Since dd57482 was merged, we
need to explicitly isntruct the optimizer to distribute these full
scans.

Release note: None

Author: rafiss

pkg/cmd/roachtest/tests/schemachange.go

@@ -433,13 +433,6 @@ func makeSchemaChangeBulkIngestTest(
 				db := c.Conn(ctx, t.L(), 1)
 				defer db.Close()
 
-				// TODO(152859): Temporarily disable soft limit for distribute scan to
-				// test performance regression fix (see #152295).
-				t.L().Printf("Setting use_soft_limit_for_distribute_scan = false")
-				if _, err := db.Exec("SET use_soft_limit_for_distribute_scan = false"); err != nil {
-					t.Fatal(err)
-				}
-
 				t.L().Printf("Computing table statistics manually")
 				if _, err := db.Exec("CREATE STATISTICS stats from bulkingest.bulkingest"); err != nil {
 					t.Fatal(err)

pkg/sql/backfill.go

@@ -1541,6 +1541,10 @@ func ValidateConstraint(
 	runHistoricalTxn descs.HistoricalInternalExecTxnRunner,
 	execOverride sessiondata.InternalExecutorOverride,
 ) (err error) {
+	// Validation queries use full table scans which we always want to distribute.
+	// See https://github.com/cockroachdb/cockroach/issues/152859.
+	execOverride.AlwaysDistributeFullScans = true
+
 	tableDesc, err = tableDesc.MakeFirstMutationPublic(catalog.IgnoreConstraints)
 	if err != nil {
 		return err
@@ -1666,6 +1670,10 @@ func ValidateInvertedIndexes(
 	execOverride sessiondata.InternalExecutorOverride,
 	protectedTSManager scexec.ProtectedTimestampManager,
 ) (err error) {
+	// Validation queries use full table scans which we always want to distribute.
+	// See https://github.com/cockroachdb/cockroach/issues/152859.
+	execOverride.AlwaysDistributeFullScans = true
+
 	grp := ctxgroup.WithContext(ctx)
 	invalid := make(chan descpb.IndexID, len(indexes))
 
@@ -1769,6 +1777,11 @@ func countExpectedRowsForInvertedIndex(
 ) (int64, error) {
 	desc := tableDesc
 	start := timeutil.Now()
+
+	// Validation queries use full table scans which we always want to distribute.
+	// See https://github.com/cockroachdb/cockroach/issues/152859.
+	execOverride.AlwaysDistributeFullScans = true
+
 	if withFirstMutationPublic {
 		// Make the mutations public in an in-memory copy of the descriptor and
 		// add it to the Collection's synthetic descriptors, so that we can use
@@ -1867,6 +1880,10 @@ func ValidateForwardIndexes(
 	execOverride sessiondata.InternalExecutorOverride,
 	protectedTSManager scexec.ProtectedTimestampManager,
 ) (err error) {
+	// Validation queries use full table scans which we always want to distribute.
+	// See https://github.com/cockroachdb/cockroach/issues/152859.
+	execOverride.AlwaysDistributeFullScans = true
+
 	grp := ctxgroup.WithContext(ctx)
 
 	invalid := make(chan descpb.IndexID, len(indexes))
@@ -1983,6 +2000,10 @@ func populateExpectedCounts(
 	runHistoricalTxn descs.HistoricalInternalExecTxnRunner,
 	execOverride sessiondata.InternalExecutorOverride,
 ) (int64, error) {
+	// Validation queries use full table scans which we always want to distribute.
+	// See https://github.com/cockroachdb/cockroach/issues/152859.
+	execOverride.AlwaysDistributeFullScans = true
+
 	desc := tableDesc
 	if withFirstMutationPublic {
 		// The query to count the expected number of rows can reference columns
@@ -2049,6 +2070,10 @@ func countIndexRowsAndMaybeCheckUniqueness(
 	runHistoricalTxn descs.HistoricalInternalExecTxnRunner,
 	execOverride sessiondata.InternalExecutorOverride,
 ) (int64, error) {
+	// Validation queries use full table scans which we always want to distribute.
+	// See https://github.com/cockroachdb/cockroach/issues/152859.
+	execOverride.AlwaysDistributeFullScans = true
+
 	// If we are doing a REGIONAL BY ROW locality change, we can
 	// bypass the uniqueness check below as we are only adding or
 	// removing an implicit partitioning column.  Scan the

pkg/sql/check.go

@@ -63,11 +63,17 @@ func validateCheckExpr(
 		queryStr = fmt.Sprintf(`SELECT %s FROM [%d AS t]@[%d] WHERE NOT (%s) LIMIT 1`, columns, tableDesc.GetID(), indexIDForValidation, exprStr)
 	}
 	log.Dev.Infof(ctx, "validating check constraint %q with query %q", formattedCkExpr, queryStr)
+
+	// Validation queries use full table scans which we always want to distribute.
+	// See https://github.com/cockroachdb/cockroach/issues/152859.
+	execOverride := sessiondata.NodeUserSessionDataOverride
+	execOverride.AlwaysDistributeFullScans = true
+
 	violatingRow, err = txn.QueryRowEx(
 		ctx,
 		"validate check constraint",
 		txn.KV(),
-		sessiondata.NodeUserSessionDataOverride,
+		execOverride,
 		queryStr)
 	if err != nil {
 		return nil, formattedCkExpr, err

pkg/sql/internal.go

@@ -965,6 +965,9 @@ func applyOverrides(o sessiondata.InternalExecutorOverride, sd *sessiondata.Sess
 	if o.BufferedWritesEnabled != nil {
 		sd.BufferedWritesEnabled = *o.BufferedWritesEnabled
 	}
+	if o.AlwaysDistributeFullScans {
+		sd.AlwaysDistributeFullScans = true
+	}
 	// For 25.2, we're being conservative and explicitly disabling buffered
 	// writes for the internal executor.
 	// TODO(yuzefovich): remove this for 25.3.

pkg/sql/sessiondata/internal.go

@@ -87,6 +87,9 @@ type InternalExecutorOverride struct {
 	// BufferedWritesEnabled, if set, controls whether the buffered writes KV transaction
 	// protocol is used for user queries on the current session.
 	BufferedWritesEnabled *bool
+	// AlwaysDistributeFullScans, if true, overrides the
+	// always_distribute_full_scans session variable.
+	AlwaysDistributeFullScans bool
 }
 
 // NoSessionDataOverride is the empty InternalExecutorOverride which does not