v3: keyspace name qualifier support

data/test/vtgate/from_cases.txt

@@ -753,6 +753,43 @@
   }
 }
 
+# keyspace-qualified queries
+"select user.user.col1, main.main1.col1 from user.user join main.main1 where main.main1.col2 = user.user.col2"
+{
+  "Original": "select user.user.col1, main.main1.col1 from user.user join main.main1 where main.main1.col2 = user.user.col2",
+  "Instructions": {
+    "Opcode": "Join",
+    "Left": {
+      "Opcode": "SelectScatter",
+      "Keyspace": {
+        "Name": "user",
+        "Sharded": true
+      },
+      "Query": "select user.col1, user.col2 from user",
+      "FieldQuery": "select user.col1, user.col2 from user where 1 != 1"
+    },
+    "Right": {
+      "Opcode": "SelectUnsharded",
+      "Keyspace": {
+        "Name": "main",
+        "Sharded": false
+      },
+      "Query": "select main1.col1 from main1 where main1.col2 = :user_col2",
+      "FieldQuery": "select main1.col1 from main1 where 1 != 1",
+      "JoinVars": {
+        "user_col2": {}
+      }
+    },
+    "Cols": [
+      -1,
+      1
+    ],
+    "Vars": {
+      "user_col2": 1
+    }
+  }
+}
+
 # duplicate symbols
 "select user.id from user join user"
 "duplicate symbol: user"

data/test/vtgate/unsupported_cases.txt

@@ -58,10 +58,6 @@
 "select id, (select id from user) from user"
 "unsupported: scatter subquery"
 
-# keyspace name
-"select * from user.user"
-"unsupported: keyspace name qualifier for tables"
-
 # natural join
 "select * from user natural join user_extra"
 "unsupported: natural join"

go/vt/sqlparser/ast.go

@@ -646,6 +646,10 @@ type TableName struct {
 
 // Format formats the node.
 func (node *TableName) Format(buf *TrackedBuffer) {
+	// node can be nil for unqualified column names.
+	if node == nil {
+		return
+	}
 	if node.Qualifier != "" {
 		buf.Myprintf("%v.", node.Qualifier)
 	}
@@ -664,6 +668,11 @@ func (node *TableName) WalkSubtree(visit Visit) error {
 	)
 }
 
+// IsEmpty returns true if TableName is nil or empty.
+func (node *TableName) IsEmpty() bool {
+	return node == nil || (node.Qualifier == "" && node.Name == "")
+}
+
 // ParenTableExpr represents a parenthesized list of TableExpr.
 type ParenTableExpr struct {
 	Exprs TableExprs
@@ -1179,12 +1188,12 @@ type ColName struct {
 	// table or column this node references.
 	Metadata  interface{}
 	Name      SQLName
-	Qualifier SQLName
+	Qualifier *TableName
 }
 
 // Format formats the node.
 func (node *ColName) Format(buf *TrackedBuffer) {
-	if node.Qualifier != "" {
+	if !node.Qualifier.IsEmpty() {
 		buf.Myprintf("%v.", node.Qualifier)
 	}
 	buf.Myprintf("%v", node.Name)

go/vt/sqlparser/parse_test.go

@@ -307,6 +307,8 @@ func TestValid(t *testing.T) {
 		input: "select /* a */ a from t",
 	}, {
 		input: "select /* a.b */ a.b from t",
+	}, {
+		input: "select /* a.b.c */ a.b.c from t",
 	}, {
 		input:  "select /* keyword a.b */ `By`.`bY` from t",
 		output: "select /* keyword a.b */ `By`.`by` from t",