Merge pull request #137655 from cockroachdb/blathers/backport-release…

…-24.1-137584

release-24.1: sql: avoid invalid SQL in `raw_config_sql` in `crdb_internal.zones`

pkg/sql/show_zone_config.go

@@ -157,34 +157,35 @@ func getShowZoneConfigRow(
 }
 
 // zoneConfigToSQL pretty prints a zone configuration as a SQL string.
-func zoneConfigToSQL(zs *tree.ZoneSpecifier, zone *zonepb.ZoneConfig) (string, error) {
+func zoneConfigToSQL(zs *tree.ZoneSpecifier, zone *zonepb.ZoneConfig) (tree.Datum, error) {
 	constraints, err := yamlMarshalFlow(zonepb.ConstraintsList{
 		Constraints: zone.Constraints,
 		Inherited:   zone.InheritedConstraints})
 	if err != nil {
-		return "", err
+		return tree.DNull, err
 	}
 	constraints = strings.TrimSpace(constraints)
 	voterConstraints, err := yamlMarshalFlow(zonepb.ConstraintsList{
 		Constraints: zone.VoterConstraints,
 		Inherited:   zone.InheritedVoterConstraints(),
 	})
 	if err != nil {
-		return "", err
+		return tree.DNull, err
 	}
 	voterConstraints = strings.TrimSpace(voterConstraints)
 	prefs, err := yamlMarshalFlow(zone.LeasePreferences)
 	if err != nil {
-		return "", err
+		return tree.DNull, err
 	}
 	prefs = strings.TrimSpace(prefs)
 
-	useComma := false
+	first := true
 	maybeWriteComma := func(f *tree.FmtCtx) {
-		if useComma {
+		if !first {
 			f.Printf(",\n")
+		} else {
+			first = false
 		}
-		useComma = true
 	}
 
 	f := tree.NewFmtCtx(tree.FmtParsable)
@@ -227,7 +228,13 @@ func zoneConfigToSQL(zs *tree.ZoneSpecifier, zone *zonepb.ZoneConfig) (string, e
 		maybeWriteComma(f)
 		f.Printf("\tlease_preferences = %s", lexbase.EscapeSQLString(prefs))
 	}
-	return f.String(), nil
+	if first {
+		// We didn't include any zone config parameters, so rather than
+		// returning an invalid 'ALTER ... CONFIGURE ZONE USING;' stmt we'll
+		// return NULL.
+		return tree.DNull, nil
+	}
+	return tree.NewDString(f.String()), nil
 }
 
 // generateZoneConfigIntrospectionValues creates a result row
@@ -292,11 +299,12 @@ func generateZoneConfigIntrospectionValues(
 	if zs == nil {
 		values[rawConfigSQLCol] = tree.DNull
 	} else {
-		sqlStr, err := zoneConfigToSQL(zs, zone)
+		var d tree.Datum
+		d, err = zoneConfigToSQL(zs, zone)
 		if err != nil {
 			return err
 		}
-		values[rawConfigSQLCol] = tree.NewDString(sqlStr)
+		values[rawConfigSQLCol] = d
 	}
 
 	// Populate the protobuf column.
@@ -321,11 +329,12 @@ func generateZoneConfigIntrospectionValues(
 	if zs == nil {
 		values[fullConfigSQLCol] = tree.DNull
 	} else {
-		sqlStr, err := zoneConfigToSQL(zs, inheritedConfig)
+		var d tree.Datum
+		d, err = zoneConfigToSQL(zs, inheritedConfig)
 		if err != nil {
 			return err
 		}
-		values[fullConfigSQLCol] = tree.NewDString(sqlStr)
+		values[fullConfigSQLCol] = d
 	}
 	return nil
 }