Merge pull request pingcap#1039 from pingcap/coocood/fix-join-subquery

optimizer/plan: check join path subquery when attach condition.

optimizer/plan/planbuilder_join.go

@@ -272,6 +272,11 @@ func (p *joinPath) attachEqualCond(eqCon *equalCond, availablePaths []*joinPath)
 		}
 		return false
 	}
+	// subquery join
+	if p.subquery != nil {
+		// TODO: find a way to attach condition to subquery.
+		return false
+	}
 	// outer join
 	if p.outer.attachEqualCond(eqCon, availablePaths) {
 		p.filterRate *= rateEqual

session_test.go

@@ -1647,6 +1647,18 @@ func (s *testSessionSuite) TestIgnoreForeignKey(c *C) {
 	mustExecSQL(c, se, sqlText)
 }
 
+func (s *testSessionSuite) TestJoinSubquery(c *C) {
+	store := newStore(c, s.dbName)
+	se := newSession(c, store, s.dbName)
+	mustExecSQL(c, se, "CREATE TABLE table1 (id INTEGER key AUTO_INCREMENT, data VARCHAR(30))")
+	mustExecSQL(c, se, "CREATE TABLE table2 (id INTEGER key AUTO_INCREMENT, data VARCHAR(30), t1id INTEGER)")
+	sqlTxt := `SELECT table1.id AS table1_id, table1.data AS table1_data FROM
+	table1 INNER JOIN (
+		SELECT table2.id AS id, table2.data AS ata, table2.t1id AS t1id FROM table2
+	) AS anon_1 ON table1.id = anon_1.t1id;`
+	mustExecSQL(c, se, sqlTxt)
+}
+
 func (s *testSessionSuite) TestGlobalVarAccessor(c *C) {
 
 	varName := "max_allowed_packet"