planner: fix bugs related to TIDB_INLJ hint (#11253)

planner/core/exhaust_physical_plans.go

@@ -1030,15 +1030,19 @@ func (p *LogicalJoin) tryToGetIndexJoin(prop *property.PhysicalProperty) (indexJ
 		}
 
 		if leftJoins != nil && lhsCardinality < rhsCardinality {
-			return leftJoins, hasIndexJoinHint
+			return leftJoins, leftOuter
 		}
 
 		if rightJoins != nil && rhsCardinality < lhsCardinality {
-			return rightJoins, hasIndexJoinHint
+			return rightJoins, rightOuter
 		}
 
+		canForceLeft := leftJoins != nil && leftOuter
+		canForceRight := rightJoins != nil && rightOuter
+		forced = canForceLeft || canForceRight
+
 		joins := append(leftJoins, rightJoins...)
-		return joins, hasIndexJoinHint && len(joins) != 0
+		return joins, forced
 	}
 
 	return nil, false

planner/core/logical_plan_builder.go

@@ -310,8 +310,17 @@ func (p *LogicalJoin) extractOnCondition(conditions []expression.Expression, der
 	return
 }
 
+// extractTableAlias returns table alias of the LogicalPlan's columns.
+// It will return nil when there are multiple table alias, because the alias is only used to check if
+// the logicalPlan match some optimizer hints, and hints are not expected to take effect in this case.
 func extractTableAlias(p LogicalPlan) *model.CIStr {
 	if p.Schema().Len() > 0 && p.Schema().Columns[0].TblName.L != "" {
+		tblName := p.Schema().Columns[0].TblName.L
+		for _, column := range p.Schema().Columns {
+			if column.TblName.L != tblName {
+				return nil
+			}
+		}
 		return &(p.Schema().Columns[0].TblName)
 	}
 	return nil

planner/core/physical_plan_test.go

@@ -1518,3 +1518,52 @@ func (s *testPlanSuite) TestUnmatchedTableInHint(c *C) {
 		}
 	}
 }
+
+func (s *testPlanSuite) TestIndexJoinHint(c *C) {
+	defer testleak.AfterTest(c)()
+	store, dom, err := newStoreWithBootstrap()
+	c.Assert(err, IsNil)
+	defer func() {
+		dom.Close()
+		store.Close()
+	}()
+	se, err := session.CreateSession4Test(store)
+	c.Assert(err, IsNil)
+	_, err = se.Execute(context.Background(), "use test")
+	c.Assert(err, IsNil)
+
+	tests := []struct {
+		sql     string
+		best    string
+		warning string
+	}{
+		{
+			sql:     "select /*+ TIDB_INLJ(t1) */ t1.a, t2.a, t3.a from t t1, t t2, t t3 where t1.a = t2.a and t2.a = t3.a;",
+			best:    "MergeInnerJoin{TableReader(Table(t))->IndexJoin{TableReader(Table(t))->TableReader(Table(t))}(test.t2.a,test.t1.a)}(test.t3.a,test.t2.a)->Projection",
+			warning: "",
+		},
+		{
+			sql:     "select /*+ TIDB_INLJ(t1) */ t1.b, t2.a from t t1, t t2 where t1.b = t2.a;",
+			best:    "LeftHashJoin{TableReader(Table(t))->TableReader(Table(t))}(test.t1.b,test.t2.a)",
+			warning: "[planner:1815]Optimizer Hint /*+ TIDB_INLJ(t1) */ is inapplicable",
+		},
+	}
+	for i, test := range tests {
+		comment := Commentf("case:%v sql:%s", i, test)
+		stmt, err := s.ParseOneStmt(test.sql, "", "")
+		c.Assert(err, IsNil, comment)
+
+		p, err := planner.Optimize(se, stmt, s.is)
+		c.Assert(err, IsNil)
+		c.Assert(core.ToString(p), Equals, test.best)
+
+		warnings := se.GetSessionVars().StmtCtx.GetWarnings()
+		if test.warning == "" {
+			c.Assert(len(warnings), Equals, 0)
+		} else {
+			c.Assert(len(warnings), Equals, 1)
+			c.Assert(warnings[0].Level, Equals, stmtctx.WarnLevelWarning)
+			c.Assert(warnings[0].Err.Error(), Equals, test.warning)
+		}
+	}
+}