fix: information schema for non existent schema

go/sqltypes/bind_variables.go

@@ -27,8 +27,16 @@ import (
 	querypb "vitess.io/vitess/go/vt/proto/query"
 )
 
-// NullBindVariable is a bindvar with NULL value.
-var NullBindVariable = &querypb.BindVariable{Type: querypb.Type_NULL_TYPE}
+var (
+	// BvSchemaName is bind variable to be sent down to vttablet for schema name.
+	BvSchemaName = "__vtschemaname"
+
+	// BvReplaceSchemaName is bind variable to be sent down to vttablet to replace schema name.
+	BvReplaceSchemaName = "__replacevtschemaname"
+
+	// NullBindVariable is a bindvar with NULL value.
+	NullBindVariable = &querypb.BindVariable{Type: querypb.Type_NULL_TYPE}
+)
 
 // ValueToProto converts Value to a *querypb.Value.
 func ValueToProto(v Value) *querypb.Value {

go/test/endtoend/vtgate/misc_test.go

@@ -317,6 +317,10 @@ func TestInformationSchemaQuery(t *testing.T) {
 	require.Nil(t, err)
 	assert.Equal(t, 1, len(qr.Rows), "did not get enough rows back")
 	assert.Equal(t, "vt_ks", qr.Rows[0][0].ToString())
+
+	qr, err = conn.ExecuteFetch("SELECT distinct table_schema FROM information_schema.tables WHERE table_schema = 'NONE'", 1000, true)
+	require.Nil(t, err)
+	assert.Empty(t, qr.Rows)
 }
 
 func TestOffsetAndLimitWithOLAP(t *testing.T) {

go/vt/vtexplain/vtexplain_flaky_test.go

@@ -216,7 +216,6 @@ func TestJSONOutput(t *testing.T) {
             {
                 "BindVars": {
                     "#maxLimit": "10001",
-                    "__vtschemaname": "''",
                     "vtg1": "1"
                 },
                 "SQL": "select :vtg1 from user where id = :vtg1",

go/vt/vtgate/engine/route.go

@@ -186,8 +186,6 @@ var routeName = map[RouteOpcode]string{
 
 var (
 	partialSuccessScatterQueries = stats.NewCounter("PartialSuccessScatterQueries", "Count of partially successful scatter queries")
-	// BvSchemaName is bind variable to be sent down to vttablet for schema name.
-	BvSchemaName = "__vtschemaname"
 )
 
 // MarshalJSON serializes the RouteOpcode as a JSON string.
@@ -386,14 +384,16 @@ func (route *Route) paramsSystemQuery(vcursor VCursor, bindVars map[string]*quer
 	}
 
 	var keyspace string
+	schemaExists := false
 	for _, expr := range route.SysTableKeyspaceExpr {
 		result, err := expr.Evaluate(env)
 		if err != nil {
 			return nil, nil, err
 		}
 		if keyspace == "" {
 			keyspace = result.Value().ToString()
-			bindVars[BvSchemaName] = sqltypes.StringBindVariable(keyspace)
+			bindVars[sqltypes.BvSchemaName] = sqltypes.StringBindVariable(keyspace)
+			schemaExists = true
 		} else if other := result.Value().ToString(); keyspace != other {
 			return nil, nil, vterrors.Errorf(vtrpcpb.Code_INVALID_ARGUMENT, "can't use more than one keyspace per system table query - found both '%s' and '%s'", keyspace, other)
 		}
@@ -404,7 +404,12 @@ func (route *Route) paramsSystemQuery(vcursor VCursor, bindVars map[string]*quer
 	}
 
 	destinations, _, err := vcursor.ResolveDestinations(keyspace, nil, []key.Destination{key.DestinationAnyShard{}})
-	if err != nil {
+	if err == nil {
+		// This is to indicate vttablet to replace the schema name.
+		if schemaExists {
+			bindVars[sqltypes.BvReplaceSchemaName] = sqltypes.Int64BindVariable(1)
+		}
+	} else {
 		// Check with assigned route keyspace.
 		destinations, _, err = vcursor.ResolveDestinations(route.Keyspace.Name, nil, []key.Destination{key.DestinationAnyShard{}})
 		if err != nil {

go/vt/vtgate/planbuilder/select.go

@@ -20,6 +20,8 @@ import (
 	"errors"
 	"fmt"
 
+	"vitess.io/vitess/go/sqltypes"
+
 	"vitess.io/vitess/go/vt/key"
 
 	vtrpcpb "vitess.io/vitess/go/vt/proto/vtrpc"
@@ -257,7 +259,7 @@ func (r *rewriter) rewriteTableSchema(cursor *sqlparser.Cursor) bool {
 						return false
 					}
 					r.tableNameExpressions = append(r.tableNameExpressions, evalExpr)
-					parent.Right = sqlparser.NewArgument([]byte(":" + engine.BvSchemaName))
+					parent.Right = sqlparser.NewArgument([]byte(":" + sqltypes.BvSchemaName))
 				}
 			}
 		}

go/vt/vttablet/tabletserver/query_executor.go

@@ -124,7 +124,9 @@ func (qre *QueryExecutor) Execute() (reply *sqltypes.Result, err error) {
 	case planbuilder.PlanSelect, planbuilder.PlanSelectImpossible, planbuilder.PlanShowTables:
 		maxrows := qre.getSelectLimit()
 		qre.bindVars["#maxLimit"] = sqltypes.Int64BindVariable(maxrows + 1)
-		qre.bindVars["__vtschemaname"] = sqltypes.StringBindVariable(qre.tsv.config.DB.DBName)
+		if qre.bindVars[sqltypes.BvReplaceSchemaName] != nil {
+			qre.bindVars[sqltypes.BvSchemaName] = sqltypes.StringBindVariable(qre.tsv.config.DB.DBName)
+		}
 		qr, err := qre.execSelect()
 		if err != nil {
 			return nil, err
@@ -207,7 +209,9 @@ func (qre *QueryExecutor) txConnExec(conn *StatefulConnection) (*sqltypes.Result
 	case planbuilder.PlanSelect, planbuilder.PlanSelectLock, planbuilder.PlanSelectImpossible, planbuilder.PlanShowTables:
 		maxrows := qre.getSelectLimit()
 		qre.bindVars["#maxLimit"] = sqltypes.Int64BindVariable(maxrows + 1)
-		qre.bindVars["__vtschemaname"] = sqltypes.StringBindVariable(qre.tsv.config.DB.DBName)
+		if qre.bindVars[sqltypes.BvReplaceSchemaName] != nil {
+			qre.bindVars[sqltypes.BvSchemaName] = sqltypes.StringBindVariable(qre.tsv.config.DB.DBName)
+		}
 		qr, err := qre.txFetch(conn, false)
 		if err != nil {
 			return nil, err