cherry pick pingcap#20992 to release-4.0

Signed-off-by: ti-srebot <ti-srebot@pingcap.com>
eurekaka · Nov 27, 2020 · 94f3dbb · 94f3dbb
1 parent 0bcb1b5
commit 94f3dbb
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Showing 2 changed files with 22 additions and 0 deletions.
diff --git a/planner/core/hints.go b/planner/core/hints.go
@@ -45,6 +45,11 @@ func getTableName(tblName model.CIStr, asName *model.CIStr) model.CIStr {
 }
 
 func extractTableAsName(p PhysicalPlan) (*model.CIStr, *model.CIStr) {
+	_, isProj := p.(*PhysicalProjection)
+	_, isUnionScan := p.(*PhysicalUnionScan)
+	if isProj || isUnionScan {
+		return extractTableAsName(p.Children()[0])
+	}
 	if len(p.Children()) > 1 {
 		return nil, nil
 	}

diff --git a/planner/core/physical_plan_test.go b/planner/core/physical_plan_test.go
@@ -784,6 +784,23 @@ func (s *testPlanSuite) TestAggregationHints(c *C) {
 	}
 }
 
+func (s *testPlanSuite) TestExplainJoinHints(c *C) {
+	defer testleak.AfterTest(c)()
+	store, dom, err := newStoreWithBootstrap()
+	c.Assert(err, IsNil)
+	defer func() {
+		dom.Close()
+		store.Close()
+	}()
+	tk := testkit.NewTestKit(c, store)
+	tk.MustExec("use test")
+	tk.MustExec("drop table if exists t")
+	tk.MustExec("create table t(a int, b int, c int, key(b), key(c))")
+	tk.MustQuery("explain format='hint' select /*+ inl_hash_join(t2) */ * from t t1 inner join t t2 on t1.b = t2.b and t1.c = 1").Check(testkit.Rows(
+		"use_index(@`sel_1` `test`.`t1` `c`), use_index(@`sel_1` `test`.`t2` `b`), inl_hash_join(@`sel_1` `test`.`t2`), inl_hash_join(`t2`)",
+	))
+}
+
 func (s *testPlanSuite) TestAggToCopHint(c *C) {
 	defer testleak.AfterTest(c)()
 	store, dom, err := newStoreWithBootstrap()