Adds support for update by destination

data/test/vtgate/dml_cases.txt

@@ -1306,6 +1306,21 @@
   }
 }
 
+# update with target destination
+"update `user[-]`.user_extra set val = 1"
+{
+  "Original": "update `user[-]`.user_extra set val = 1",
+  "Instructions": {
+    "Opcode": "UpdateByDestination",
+    "Keyspace": {
+      "Name": "user",
+      "Sharded": true
+    },
+    "Query": "update user_extra set val = 1",
+    "Table": "user_extra"
+  }
+}
+
 # update with no primary vindex on where clause (scatter update)   - multi shard autocommit
 "update /*vt+ MULTI_SHARD_AUTOCOMMIT=1 */  user_extra set val = 1"
 {

data/test/vtgate/unsupported_cases.txt

@@ -39,10 +39,6 @@
 "select * from `user[-]`.user_metadata"
 "unsupported: SELECT with a target destination"
 
-# Unsupported UPDATE statement with a target destination
-"update `user[-]`.user_metadata set id=2"
-"unsupported: UPDATE with a target destination"
-
 # Unsupported INSERT statement with a target destination
 "insert into `user[-]`.user_metadata (a, b) values (1,2)"
 "unsupported: INSERT with a target destination"
@@ -51,6 +47,10 @@
 "DELETE FROM `user[-]@replica`.user_metadata limit 1"
 "unsupported: DELETE statement with a replica target"
 
+# Unsupported UPDATE statement with a replica target destination
+"update `user[-]@replica`.user_metadata set id=2"
+"unsupported: UPDATE statement with a replica target"
+
 # order by on a cross-shard subquery
 "select id from (select user.id, user.col from user join user_extra) as t order by id"
 "unsupported: cannot order by on a cross-shard subquery"

go/vt/vtgate/engine/route.go

@@ -32,6 +32,7 @@ import (
 	"vitess.io/vitess/go/vt/vtgate/vindexes"
 
 	querypb "vitess.io/vitess/go/vt/proto/query"
+	topodatapb "vitess.io/vitess/go/vt/proto/topodata"
 )
 
 var _ Primitive = (*Route)(nil)
@@ -50,6 +51,10 @@ type Route struct {
 	// This bypases the core of the v3 engine.
 	TargetDestination key.Destination
 
+	// TargetTabletType specifies an explicit target destination tablet type
+	// this is only used in conjunction with TargetDestination
+	TargetTabletType topodatapb.TabletType
+
 	// Query specifies the query to be executed.
 	Query string
 

go/vt/vtgate/engine/update.go

@@ -42,6 +42,9 @@ type Update struct {
 	// Keyspace specifies the keyspace to send the query to.
 	Keyspace *vindexes.Keyspace
 
+	// TargetDestination specifies the destination to send the query to.
+	TargetDestination key.Destination
+
 	// Query specifies the query to be executed.
 	Query string
 
@@ -115,12 +118,18 @@ const (
 	// UpdateScatter is for routing a scattered
 	// update statement.
 	UpdateScatter
+	// UpdateByDestination is to route explicitly to a given
+	// target destination. Is used when the query explicitly sets a target destination:
+	// in the clause:
+	// e.g: UPDATE `keyspace[-]`.x1 SET foo=1
+	UpdateByDestination
 )
 
 var updName = map[UpdateOpcode]string{
-	UpdateUnsharded: "UpdateUnsharded",
-	UpdateEqual:     "UpdateEqual",
-	UpdateScatter:   "UpdateScatter",
+	UpdateUnsharded:     "UpdateUnsharded",
+	UpdateEqual:         "UpdateEqual",
+	UpdateScatter:       "UpdateScatter",
+	UpdateByDestination: "UpdateByDestination",
 }
 
 // MarshalJSON serializes the UpdateOpcode as a JSON string.
@@ -143,6 +152,8 @@ func (upd *Update) Execute(vcursor VCursor, bindVars map[string]*querypb.BindVar
 		return upd.execUpdateEqual(vcursor, bindVars)
 	case UpdateScatter:
 		return upd.execUpdateByDestination(vcursor, bindVars, key.DestinationAllShards{})
+	case UpdateByDestination:
+		return upd.execUpdateByDestination(vcursor, bindVars, upd.TargetDestination)
 	default:
 		// Unreachable.
 		return nil, fmt.Errorf("unsupported opcode: %v", upd)

go/vt/vtgate/planbuilder/from.go

@@ -157,7 +157,7 @@ func (pb *primitiveBuilder) buildTablePrimitive(tableExpr *sqlparser.AliasedTabl
 		return nil
 	}
 
-	table, vindex, _, _, destTarget, err := pb.vschema.FindTableOrVindex(tableName)
+	table, vindex, _, destTableType, destTarget, err := pb.vschema.FindTableOrVindex(tableName)
 	if err != nil {
 		return err
 	}
@@ -183,6 +183,7 @@ func (pb *primitiveBuilder) buildTablePrimitive(tableExpr *sqlparser.AliasedTabl
 			Opcode:            engine.SelectScatter,
 			Keyspace:          table.Keyspace,
 			TargetDestination: destTarget,
+			TargetTabletType:  destTableType,
 		}
 		return nil
 	}

go/vt/vtgate/planbuilder/update.go

@@ -25,6 +25,7 @@ import (
 	"vitess.io/vitess/go/vt/vtgate/engine"
 	"vitess.io/vitess/go/vt/vtgate/vindexes"
 
+	topodatapb "vitess.io/vitess/go/vt/proto/topodata"
 	vtrpcpb "vitess.io/vitess/go/vt/proto/vtrpc"
 )
 
@@ -42,9 +43,6 @@ func buildUpdatePlan(upd *sqlparser.Update, vschema ContextVSchema) (*engine.Upd
 	if !ok {
 		return nil, errors.New("unsupported: multi-table/vindex update statement in sharded keyspace")
 	}
-	if rb.ERoute.TargetDestination != nil {
-		return nil, errors.New("unsupported: UPDATE with a target destination")
-	}
 	eupd.Keyspace = rb.ERoute.Keyspace
 	if !eupd.Keyspace.Sharded {
 		// We only validate non-table subexpressions because the previous analysis has already validated them.
@@ -76,6 +74,16 @@ func buildUpdatePlan(upd *sqlparser.Update, vschema ContextVSchema) (*engine.Upd
 		return nil, errors.New("internal error: table.vindexTable is mysteriously nil")
 	}
 	var err error
+
+	if rb.ERoute.TargetDestination != nil {
+		if rb.ERoute.TargetTabletType != topodatapb.TabletType_MASTER {
+			return nil, vterrors.Errorf(vtrpcpb.Code_INVALID_ARGUMENT, "unsupported: UPDATE statement with a replica target")
+		}
+		eupd.Opcode = engine.UpdateByDestination
+		eupd.TargetDestination = rb.ERoute.TargetDestination
+		return eupd, nil
+	}
+
 	eupd.Vindex, eupd.Values, err = getDMLRouting(upd.Where, eupd.Table)
 	if err != nil {
 		eupd.Opcode = engine.UpdateScatter