planner: support no_merge_join hint on optimizer

planner/core/casetest/rule/rule_join_reorder_test.go

@@ -72,6 +72,17 @@ func TestNoHashJoinHint(t *testing.T) {
 	runJoinReorderTestData(t, tk, "TestNoHashJoinHint")
 }
 
+func TestNoMergeJoinHint(t *testing.T) {
+	store := testkit.CreateMockStore(t)
+	tk := testkit.NewTestKit(t, store)
+	tk.MustExec("use test")
+	tk.MustExec("create table t1(a int, key(a));")
+	tk.MustExec("create table t2(a int, key(a));")
+	tk.MustExec("create table t3(a int, key(a));")
+	tk.MustExec("create table t4(a int, key(a));")
+	runJoinReorderTestData(t, tk, "TestNoMergeJoinHint")
+}
+
 func TestLeadingJoinHint(t *testing.T) {
 	store := testkit.CreateMockStore(t)
 

planner/core/casetest/rule/testdata/join_reorder_suite_in.json

@@ -49,6 +49,19 @@
       "select /*+ leading(t1, t2, t3, t4), hash_join(t1, t2), no_hash_join(t3), hash_join(t4) */ * from t1, t2, t3, t4"
     ]
   },
+  {
+    "name": "TestNoMergeJoinHint",
+    "cases": [
+      "select /*+ no_merge_join() */ * from t1, t2 where t1.a=t2.a",
+      "select /*+ no_merge_join(t1), merge_join(t1) */ * from t1, t2 where t1.a=t2.a",
+      "select /*+ no_merge_join(t1), merge_join(t2) */ * from t1, t2 where t1.a=t2.a",
+      "select /*+ no_merge_join(t1) */ * from t1, t2 where t1.a=t2.a",
+      "select /*+ no_merge_join(t1, t2) */ * from t1, t2 where t1.a=t2.a",
+      "select /*+ no_merge_join(t2) */ * from t1 right join t2 on t1.a=t2.a",
+      "select /*+ leading(t4, t3, t2, t1), no_merge_join(t2, t3) */ * from t1, t2, t3, t4 where t1.a=t2.a and t2.a=t3.a and t3.a=t4.a",
+      "select /*+ leading(t1, t2, t3, t4), merge_join(t1, t2), no_merge_join(t3), merge_join(t4) */ * from t1, t2, t3, t4 where t1.a=t2.a and t2.a=t3.a and t3.a=t4.a"
+    ]
+  },
   {
     "name": "TestLeadingJoinHint",
     "cases": [

planner/core/casetest/rule/testdata/join_reorder_suite_out.json

@@ -782,6 +782,119 @@
       }
     ]
   },
+  {
+    "Name": "TestNoMergeJoinHint",
+    "Cases": [
+      {
+        "SQL": "select /*+ no_merge_join() */ * from t1, t2 where t1.a=t2.a",
+        "Plan": [
+          "MergeJoin 12487.50 root  inner join, left key:test.t1.a, right key:test.t2.a",
+          "├─IndexReader(Build) 9990.00 root  index:IndexFullScan",
+          "│ └─IndexFullScan 9990.00 cop[tikv] table:t2, index:a(a) keep order:true, stats:pseudo",
+          "└─IndexReader(Probe) 9990.00 root  index:IndexFullScan",
+          "  └─IndexFullScan 9990.00 cop[tikv] table:t1, index:a(a) keep order:true, stats:pseudo"
+        ],
+        "Warning": [
+          "Warning 1815 Hint no_merge_join() is inapplicable. Please specify the table names in the arguments."
+        ]
+      },
+      {
+        "SQL": "select /*+ no_merge_join(t1), merge_join(t1) */ * from t1, t2 where t1.a=t2.a",
+        "Plan": [
+          "MergeJoin 12487.50 root  inner join, left key:test.t1.a, right key:test.t2.a",
+          "├─IndexReader(Build) 9990.00 root  index:IndexFullScan",
+          "│ └─IndexFullScan 9990.00 cop[tikv] table:t2, index:a(a) keep order:true, stats:pseudo",
+          "└─IndexReader(Probe) 9990.00 root  index:IndexFullScan",
+          "  └─IndexFullScan 9990.00 cop[tikv] table:t1, index:a(a) keep order:true, stats:pseudo"
+        ],
+        "Warning": [
+          "Warning 1815 Some MERGE_JOIN and NO_MERGE_JOIN hints conflict, NO_MERGE_JOIN is ignored"
+        ]
+      },
+      {
+        "SQL": "select /*+ no_merge_join(t1), merge_join(t2) */ * from t1, t2 where t1.a=t2.a",
+        "Plan": [
+          "MergeJoin 12487.50 root  inner join, left key:test.t1.a, right key:test.t2.a",
+          "├─IndexReader(Build) 9990.00 root  index:IndexFullScan",
+          "│ └─IndexFullScan 9990.00 cop[tikv] table:t2, index:a(a) keep order:true, stats:pseudo",
+          "└─IndexReader(Probe) 9990.00 root  index:IndexFullScan",
+          "  └─IndexFullScan 9990.00 cop[tikv] table:t1, index:a(a) keep order:true, stats:pseudo"
+        ],
+        "Warning": [
+          "Warning 1815 Some MERGE_JOIN and NO_MERGE_JOIN hints conflict, NO_MERGE_JOIN is ignored"
+        ]
+      },
+      {
+        "SQL": "select /*+ no_merge_join(t1) */ * from t1, t2 where t1.a=t2.a",
+        "Plan": [
+          "HashJoin 12487.50 root  inner join, equal:[eq(test.t1.a, test.t2.a)]",
+          "├─IndexReader(Build) 9990.00 root  index:IndexFullScan",
+          "│ └─IndexFullScan 9990.00 cop[tikv] table:t2, index:a(a) keep order:false, stats:pseudo",
+          "└─IndexReader(Probe) 9990.00 root  index:IndexFullScan",
+          "  └─IndexFullScan 9990.00 cop[tikv] table:t1, index:a(a) keep order:false, stats:pseudo"
+        ],
+        "Warning": null
+      },
+      {
+        "SQL": "select /*+ no_merge_join(t1, t2) */ * from t1, t2 where t1.a=t2.a",
+        "Plan": [
+          "HashJoin 12487.50 root  inner join, equal:[eq(test.t1.a, test.t2.a)]",
+          "├─IndexReader(Build) 9990.00 root  index:IndexFullScan",
+          "│ └─IndexFullScan 9990.00 cop[tikv] table:t2, index:a(a) keep order:false, stats:pseudo",
+          "└─IndexReader(Probe) 9990.00 root  index:IndexFullScan",
+          "  └─IndexFullScan 9990.00 cop[tikv] table:t1, index:a(a) keep order:false, stats:pseudo"
+        ],
+        "Warning": null
+      },
+      {
+        "SQL": "select /*+ no_merge_join(t2) */ * from t1 right join t2 on t1.a=t2.a",
+        "Plan": [
+          "HashJoin 12487.50 root  right outer join, equal:[eq(test.t1.a, test.t2.a)]",
+          "├─IndexReader(Build) 9990.00 root  index:IndexFullScan",
+          "│ └─IndexFullScan 9990.00 cop[tikv] table:t1, index:a(a) keep order:false, stats:pseudo",
+          "└─IndexReader(Probe) 10000.00 root  index:IndexFullScan",
+          "  └─IndexFullScan 10000.00 cop[tikv] table:t2, index:a(a) keep order:false, stats:pseudo"
+        ],
+        "Warning": null
+      },
+      {
+        "SQL": "select /*+ leading(t4, t3, t2, t1), no_merge_join(t2, t3) */ * from t1, t2, t3, t4 where t1.a=t2.a and t2.a=t3.a and t3.a=t4.a",
+        "Plan": [
+          "Projection 19511.72 root  test.t1.a, test.t2.a, test.t3.a, test.t4.a",
+          "└─HashJoin 19511.72 root  inner join, equal:[eq(test.t2.a, test.t1.a)]",
+          "  ├─IndexReader(Build) 9990.00 root  index:IndexFullScan",
+          "  │ └─IndexFullScan 9990.00 cop[tikv] table:t1, index:a(a) keep order:false, stats:pseudo",
+          "  └─HashJoin(Probe) 15609.38 root  inner join, equal:[eq(test.t3.a, test.t2.a)]",
+          "    ├─IndexReader(Build) 9990.00 root  index:IndexFullScan",
+          "    │ └─IndexFullScan 9990.00 cop[tikv] table:t2, index:a(a) keep order:false, stats:pseudo",
+          "    └─HashJoin(Probe) 12487.50 root  inner join, equal:[eq(test.t4.a, test.t3.a)]",
+          "      ├─IndexReader(Build) 9990.00 root  index:IndexFullScan",
+          "      │ └─IndexFullScan 9990.00 cop[tikv] table:t3, index:a(a) keep order:false, stats:pseudo",
+          "      └─IndexReader(Probe) 9990.00 root  index:IndexFullScan",
+          "        └─IndexFullScan 9990.00 cop[tikv] table:t4, index:a(a) keep order:false, stats:pseudo"
+        ],
+        "Warning": null
+      },
+      {
+        "SQL": "select /*+ leading(t1, t2, t3, t4), merge_join(t1, t2), no_merge_join(t3), merge_join(t4) */ * from t1, t2, t3, t4 where t1.a=t2.a and t2.a=t3.a and t3.a=t4.a",
+        "Plan": [
+          "MergeJoin 19511.72 root  inner join, left key:test.t3.a, right key:test.t4.a",
+          "├─IndexReader(Build) 9990.00 root  index:IndexFullScan",
+          "│ └─IndexFullScan 9990.00 cop[tikv] table:t4, index:a(a) keep order:true, stats:pseudo",
+          "└─Sort(Probe) 15609.38 root  test.t3.a",
+          "  └─HashJoin 15609.38 root  inner join, equal:[eq(test.t2.a, test.t3.a)]",
+          "    ├─IndexReader(Build) 9990.00 root  index:IndexFullScan",
+          "    │ └─IndexFullScan 9990.00 cop[tikv] table:t3, index:a(a) keep order:false, stats:pseudo",
+          "    └─MergeJoin(Probe) 12487.50 root  inner join, left key:test.t1.a, right key:test.t2.a",
+          "      ├─IndexReader(Build) 9990.00 root  index:IndexFullScan",
+          "      │ └─IndexFullScan 9990.00 cop[tikv] table:t2, index:a(a) keep order:true, stats:pseudo",
+          "      └─IndexReader(Probe) 9990.00 root  index:IndexFullScan",
+          "        └─IndexFullScan 9990.00 cop[tikv] table:t1, index:a(a) keep order:true, stats:pseudo"
+        ],
+        "Warning": null
+      }
+    ]
+  },
   {
     "Name": "TestLeadingJoinHint",
     "Cases": [

planner/core/exhaust_physical_plans.go

@@ -231,6 +231,16 @@ func (p *LogicalJoin) GetMergeJoin(prop *property.PhysicalProperty, schema *expr
 			joins = append(joins, mergeJoin)
 		}
 	}
+
+	if p.preferJoinType&preferNoMergeJoin > 0 {
+		if p.preferJoinType&preferMergeJoin > 0 {
+			p.ctx.GetSessionVars().StmtCtx.AppendWarning(ErrInternal.GenWithStack(
+				"Some MERGE_JOIN and NO_MERGE_JOIN hints conflict, NO_MERGE_JOIN is ignored"))
+		} else {
+			return nil
+		}
+	}
+
 	// If TiDB_SMJ hint is existed, it should consider enforce merge join,
 	// because we can't trust lhsChildProperty completely.
 	if (p.preferJoinType&preferMergeJoin) > 0 ||

planner/core/logical_plan_builder.go

@@ -75,6 +75,8 @@ const (
 	TiDBMergeJoin = "tidb_smj"
 	// HintSMJ is hint enforce merge join.
 	HintSMJ = "merge_join"
+	// HintNoMergeJoin is the hint to enforce the query not to use merge join.
+	HintNoMergeJoin = "no_merge_join"
 
 	// TiDBBroadCastJoin indicates applying broadcast join by force.
 	TiDBBroadCastJoin = "tidb_bcj"
@@ -723,6 +725,14 @@ func (p *LogicalJoin) setPreferredJoinTypeAndOrder(hintInfo *tableHintInfo) {
 		p.preferJoinType |= preferMergeJoin
 		p.rightPreferJoinType |= preferMergeJoin
 	}
+	if hintInfo.ifPreferNoMergeJoin(lhsAlias) {
+		p.preferJoinType |= preferNoMergeJoin
+		p.leftPreferJoinType |= preferNoMergeJoin
+	}
+	if hintInfo.ifPreferNoMergeJoin(rhsAlias) {
+		p.preferJoinType |= preferNoMergeJoin
+		p.rightPreferJoinType |= preferNoMergeJoin
+	}
 	if hintInfo.ifPreferBroadcastJoin(lhsAlias) {
 		p.preferJoinType |= preferBCJoin
 		p.leftPreferJoinType |= preferBCJoin
@@ -3924,7 +3934,7 @@ func (b *PlanBuilder) pushTableHints(hints []*ast.TableOptimizerHint, currentLev
 	hints = b.hintProcessor.GetCurrentStmtHints(hints, currentLevel)
 	var (
 		sortMergeTables, inljTables, inlhjTables, inlmjTables, hashJoinTables, bcTables []hintTableInfo
-		noHashJoinTables                                                                []hintTableInfo
+		noHashJoinTables, noMergeJoinTables                                             []hintTableInfo
 		shuffleJoinTables                                                               []hintTableInfo
 		indexHintList, indexMergeHintList                                               []indexHintInfo
 		tiflashTables, tikvTables                                                       []hintTableInfo
@@ -3939,7 +3949,7 @@ func (b *PlanBuilder) pushTableHints(hints []*ast.TableOptimizerHint, currentLev
 	for _, hint := range hints {
 		// Set warning for the hint that requires the table name.
 		switch hint.HintName.L {
-		case TiDBMergeJoin, HintSMJ, TiDBIndexNestedLoopJoin, HintINLJ, HintINLHJ, HintINLMJ, HintNoHashJoin,
+		case TiDBMergeJoin, HintSMJ, TiDBIndexNestedLoopJoin, HintINLJ, HintINLHJ, HintINLMJ, HintNoHashJoin, HintNoMergeJoin,
 			TiDBHashJoin, HintHJ, HintUseIndex, HintIgnoreIndex, HintForceIndex, HintOrderIndex, HintNoOrderIndex, HintIndexMerge, HintLeading:
 			if len(hint.Tables) == 0 {
 				b.pushHintWithoutTableWarning(hint)
@@ -3964,6 +3974,8 @@ func (b *PlanBuilder) pushTableHints(hints []*ast.TableOptimizerHint, currentLev
 			hashJoinTables = append(hashJoinTables, tableNames2HintTableInfo(b.ctx, hint.HintName.L, hint.Tables, b.hintProcessor, currentLevel)...)
 		case HintNoHashJoin:
 			noHashJoinTables = append(noHashJoinTables, tableNames2HintTableInfo(b.ctx, hint.HintName.L, hint.Tables, b.hintProcessor, currentLevel)...)
+		case HintNoMergeJoin:
+			noMergeJoinTables = append(noMergeJoinTables, tableNames2HintTableInfo(b.ctx, hint.HintName.L, hint.Tables, b.hintProcessor, currentLevel)...)
 		case HintMPP1PhaseAgg:
 			aggHints.preferAggType |= preferMPP1PhaseAgg
 		case HintMPP2PhaseAgg:
@@ -4075,6 +4087,7 @@ func (b *PlanBuilder) pushTableHints(hints []*ast.TableOptimizerHint, currentLev
 		indexNestedLoopJoinTables: indexNestedLoopJoinTables{inljTables, inlhjTables, inlmjTables},
 		hashJoinTables:            hashJoinTables,
 		noHashJoinTables:          noHashJoinTables,
+		noMergeJoinTables:         noMergeJoinTables,
 		indexHintList:             indexHintList,
 		tiflashTables:             tiflashTables,
 		tikvTables:                tikvTables,
@@ -7320,6 +7333,7 @@ func getInnerFromParenthesesAndUnaryPlus(expr ast.ExprNode) ast.ExprNode {
 // join types.
 func containDifferentJoinTypes(preferJoinType uint) bool {
 	preferJoinType &= ^preferNoHashJoin
+	preferJoinType &= ^preferNoMergeJoin
 
 	inlMask := preferRightAsINLJInner ^ preferLeftAsINLJInner
 	inlhjMask := preferRightAsINLHJInner ^ preferLeftAsINLHJInner

planner/core/logical_plans.go

@@ -124,6 +124,7 @@ const (
 	preferHashJoin
 	preferNoHashJoin
 	preferMergeJoin
+	preferNoMergeJoin
 	preferBCJoin
 	preferShuffleJoin
 	preferRewriteSemiJoin

planner/core/planbuilder.go

@@ -97,6 +97,7 @@ type tableHintInfo struct {
 	shuffleJoinTables   []hintTableInfo
 	hashJoinTables      []hintTableInfo
 	noHashJoinTables    []hintTableInfo
+	noMergeJoinTables   []hintTableInfo
 	indexHintList       []indexHintInfo
 	tiflashTables       []hintTableInfo
 	tikvTables          []hintTableInfo
@@ -245,6 +246,10 @@ func (info *tableHintInfo) ifPreferNoHashJoin(tableNames ...*hintTableInfo) bool
 	return info.matchTableName(tableNames, info.noHashJoinTables)
 }
 
+func (info *tableHintInfo) ifPreferNoMergeJoin(tableNames ...*hintTableInfo) bool {
+	return info.matchTableName(tableNames, info.noMergeJoinTables)
+}
+
 func (info *tableHintInfo) ifPreferHJBuild(tableNames ...*hintTableInfo) bool {
 	return info.matchTableName(tableNames, info.hjBuildTables)
 }