*: add foreign key check/cascade information in explain result

cmd/explaintest/r/explain_foreign_key.result

@@ -0,0 +1,119 @@
+set @@global.tidb_enable_foreign_key=1;
+set @@foreign_key_checks=1;
+use test;
+drop table if exists t1,t2;
+create table t1 (id int key);
+create table t2 (id int key, foreign key fk(id) references t1(id) ON UPDATE CASCADE ON DELETE CASCADE);
+create table t3 (id int, unique index idx(id));
+create table t4 (id int, index idx_id(id),foreign key fk(id) references t3(id));
+create table t5 (id int key, id2 int, id3 int, unique index idx2(id2), index idx3(id3));
+create table t6 (id int,     id2 int, id3 int, index idx_id(id), index idx_id2(id2), foreign key fk_1 (id) references t5(id) ON UPDATE CASCADE ON DELETE CASCADE, foreign key fk_2 (id2) references t5(id2) ON UPDATE CASCADE, foreign key fk_3 (id3) references t5(id3) ON DELETE CASCADE);
+explain insert into t2 values (1);
+id	estRows	task	access object	operator info
+Insert_1	N/A	root		N/A
+└─Foreign_Key_Check_3	0.00	root	table:t1	foreign_key:fk, check_exist
+explain update t2 set id=id+1 where id = 1;
+id	estRows	task	access object	operator info
+Update_3	N/A	root		N/A
+└─Point_Get_1	1.00	root	table:t2	handle:1, lock
+└─Foreign_Key_Check_4	0.00	root	table:t1	foreign_key:fk, check_exist
+explain delete from t1 where id > 1;
+id	estRows	task	access object	operator info
+Delete_5	N/A	root		N/A
+└─SelectLock_7	3333.33	root		for update 0
+  └─TableReader_9	3333.33	root		data:TableRangeScan_8
+    └─TableRangeScan_8	3333.33	cop[tikv]	table:t1	range:(1,+inf], keep order:false, stats:pseudo
+└─Foreign_Key_Cascade_10	0.00	root	table:t2	foreign_key:fk, on_delete:CASCADE
+explain update t1 set id=id+1 where id = 1;
+id	estRows	task	access object	operator info
+Update_3	N/A	root		N/A
+└─Point_Get_1	1.00	root	table:t1	handle:1, lock
+└─Foreign_Key_Cascade_4	0.00	root	table:t2	foreign_key:fk, on_update:CASCADE
+explain insert into t1 values (1);
+id	estRows	task	access object	operator info
+Insert_1	N/A	root		N/A
+explain insert into t1 values (1) on duplicate key update id = 100;
+id	estRows	task	access object	operator info
+Insert_1	N/A	root		N/A
+└─Foreign_Key_Cascade_3	0.00	root	table:t2	foreign_key:fk, on_update:CASCADE
+explain insert into t4 values (1);
+id	estRows	task	access object	operator info
+Insert_1	N/A	root		N/A
+└─Foreign_Key_Check_3	0.00	root	table:t3, index:idx	foreign_key:fk, check_exist
+explain update t4 set id=id+1 where id = 1;
+id	estRows	task	access object	operator info
+Update_5	N/A	root		N/A
+└─SelectLock_7	10.00	root		for update 0
+  └─IndexReader_9	10.00	root		index:IndexRangeScan_8
+    └─IndexRangeScan_8	10.00	cop[tikv]	table:t4, index:idx_id(id)	range:[1,1], keep order:false, stats:pseudo
+└─Foreign_Key_Check_10	0.00	root	table:t3, index:idx	foreign_key:fk, check_exist
+explain delete from t3 where id > 1;
+id	estRows	task	access object	operator info
+Delete_5	N/A	root		N/A
+└─SelectLock_7	3333.33	root		for update 0
+  └─IndexReader_9	3333.33	root		index:IndexRangeScan_8
+    └─IndexRangeScan_8	3333.33	cop[tikv]	table:t3, index:idx(id)	range:(1,+inf], keep order:false, stats:pseudo
+└─Foreign_Key_Check_10	0.00	root	table:t4, index:idx_id	foreign_key:fk, check_not_exist
+explain update t3 set id=id+1 where id = 1;
+id	estRows	task	access object	operator info
+Update_3	N/A	root		N/A
+└─Point_Get_1	1.00	root	table:t3, index:idx(id)	lock
+└─Foreign_Key_Check_4	0.00	root	table:t4, index:idx_id	foreign_key:fk, check_not_exist
+explain insert into t3 values (1);
+id	estRows	task	access object	operator info
+Insert_1	N/A	root		N/A
+explain insert into t3 values (1) on duplicate key update id = 100;
+id	estRows	task	access object	operator info
+Insert_1	N/A	root		N/A
+└─Foreign_Key_Check_3	0.00	root	table:t4, index:idx_id	foreign_key:fk, check_not_exist
+explain insert into t6 values (1,1,1);
+id	estRows	task	access object	operator info
+Insert_1	N/A	root		N/A
+└─Foreign_Key_Check_3	0.00	root	table:t5	foreign_key:fk_1, check_exist
+└─Foreign_Key_Check_4	0.00	root	table:t5, index:idx2	foreign_key:fk_2, check_exist
+└─Foreign_Key_Check_5	0.00	root	table:t5, index:idx3	foreign_key:fk_3, check_exist
+explain update t6 set id=id+1, id3=id2+1 where id = 1;
+id	estRows	task	access object	operator info
+Update_5	N/A	root		N/A
+└─SelectLock_7	10.00	root		for update 0
+  └─IndexLookUp_13	10.00	root		
+    ├─IndexRangeScan_11(Build)	10.00	cop[tikv]	table:t6, index:idx_id(id)	range:[1,1], keep order:false, stats:pseudo
+    └─TableRowIDScan_12(Probe)	10.00	cop[tikv]	table:t6	keep order:false, stats:pseudo
+└─Foreign_Key_Check_14	0.00	root	table:t5	foreign_key:fk_1, check_exist
+└─Foreign_Key_Check_15	0.00	root	table:t5, index:idx3	foreign_key:fk_3, check_exist
+explain delete from t5 where id > 1;
+id	estRows	task	access object	operator info
+Delete_5	N/A	root		N/A
+└─SelectLock_7	3333.33	root		for update 0
+  └─TableReader_9	3333.33	root		data:TableRangeScan_8
+    └─TableRangeScan_8	3333.33	cop[tikv]	table:t5	range:(1,+inf], keep order:false, stats:pseudo
+└─Foreign_Key_Check_11	0.00	root	table:t6, index:idx_id2	foreign_key:fk_2, check_not_exist
+└─Foreign_Key_Cascade_10	0.00	root	table:t6, index:idx_id	foreign_key:fk_1, on_delete:CASCADE
+└─Foreign_Key_Cascade_12	0.00	root	table:t6, index:fk_3	foreign_key:fk_3, on_delete:CASCADE
+explain update t5 set id=id+1, id2=id2+1 where id = 1;
+id	estRows	task	access object	operator info
+Update_4	N/A	root		N/A
+└─Point_Get_1	1.00	root	table:t5	handle:1, lock
+└─Foreign_Key_Cascade_5	0.00	root	table:t6, index:idx_id	foreign_key:fk_1, on_update:CASCADE
+└─Foreign_Key_Cascade_6	0.00	root	table:t6, index:idx_id2	foreign_key:fk_2, on_update:CASCADE
+explain update t5 set id=id+1, id2=id2+1, id3=id3+1 where id = 1;
+id	estRows	task	access object	operator info
+Update_5	N/A	root		N/A
+└─Point_Get_1	1.00	root	table:t5	handle:1, lock
+└─Foreign_Key_Check_8	0.00	root	table:t6, index:fk_3	foreign_key:fk_3, check_not_exist
+└─Foreign_Key_Cascade_6	0.00	root	table:t6, index:idx_id	foreign_key:fk_1, on_update:CASCADE
+└─Foreign_Key_Cascade_7	0.00	root	table:t6, index:idx_id2	foreign_key:fk_2, on_update:CASCADE
+explain insert into t5 values (1,1,1);
+id	estRows	task	access object	operator info
+Insert_1	N/A	root		N/A
+explain insert into t5 values (1,1,1) on duplicate key update id = 100, id3=100;
+id	estRows	task	access object	operator info
+Insert_1	N/A	root		N/A
+└─Foreign_Key_Check_4	0.00	root	table:t6, index:fk_3	foreign_key:fk_3, check_not_exist
+└─Foreign_Key_Cascade_3	0.00	root	table:t6, index:idx_id	foreign_key:fk_1, on_update:CASCADE
+explain insert into t5 values (1,1,1) on duplicate key update id = 100, id2=100, id3=100;
+id	estRows	task	access object	operator info
+Insert_1	N/A	root		N/A
+└─Foreign_Key_Check_5	0.00	root	table:t6, index:fk_3	foreign_key:fk_3, check_not_exist
+└─Foreign_Key_Cascade_3	0.00	root	table:t6, index:idx_id	foreign_key:fk_1, on_update:CASCADE
+└─Foreign_Key_Cascade_4	0.00	root	table:t6, index:idx_id2	foreign_key:fk_2, on_update:CASCADE

cmd/explaintest/t/explain_foreign_key.test

@@ -0,0 +1,31 @@
+set @@global.tidb_enable_foreign_key=1;
+set @@foreign_key_checks=1;
+use test;
+drop table if exists t1,t2;
+create table t1 (id int key);
+create table t2 (id int key, foreign key fk(id) references t1(id) ON UPDATE CASCADE ON DELETE CASCADE);
+create table t3 (id int, unique index idx(id));
+create table t4 (id int, index idx_id(id),foreign key fk(id) references t3(id));
+create table t5 (id int key, id2 int, id3 int, unique index idx2(id2), index idx3(id3));
+create table t6 (id int,     id2 int, id3 int, index idx_id(id), index idx_id2(id2), foreign key fk_1 (id) references t5(id) ON UPDATE CASCADE ON DELETE CASCADE, foreign key fk_2 (id2) references t5(id2) ON UPDATE CASCADE, foreign key fk_3 (id3) references t5(id3) ON DELETE CASCADE);
+
+explain insert into t2 values (1);
+explain update t2 set id=id+1 where id = 1;
+explain delete from t1 where id > 1;
+explain update t1 set id=id+1 where id = 1;
+explain insert into t1 values (1);
+explain insert into t1 values (1) on duplicate key update id = 100;
+explain insert into t4 values (1);
+explain update t4 set id=id+1 where id = 1;
+explain delete from t3 where id > 1;
+explain update t3 set id=id+1 where id = 1;
+explain insert into t3 values (1);
+explain insert into t3 values (1) on duplicate key update id = 100;
+explain insert into t6 values (1,1,1);
+explain update t6 set id=id+1, id3=id2+1 where id = 1;
+explain delete from t5 where id > 1;
+explain update t5 set id=id+1, id2=id2+1 where id = 1;
+explain update t5 set id=id+1, id2=id2+1, id3=id3+1 where id = 1;
+explain insert into t5 values (1,1,1);
+explain insert into t5 values (1,1,1) on duplicate key update id = 100, id3=100;
+explain insert into t5 values (1,1,1) on duplicate key update id = 100, id2=100, id3=100;

planner/core/encode.go

@@ -275,8 +275,14 @@ func NormalizeFlatPlan(flat *FlatPhysicalPlan) (normalized string, digest *parse
 	// assume an operator costs around 30 bytes, preallocate space for them
 	d.buf.Grow(30 * len(selectPlan))
 	depthOffset := len(flat.Main) - len(selectPlan)
+loop1:
 	for _, op := range selectPlan {
 		taskTypeInfo := plancodec.EncodeTaskTypeForNormalize(op.IsRoot, op.StoreType)
+		switch op.Origin.(type) {
+		case *FKCheck, *FKCascade:
+			// Generate plan digest doesn't need to contain the foreign key check/cascade plan, so just break the loop.
+			break loop1
+		}
 		p := op.Origin.(PhysicalPlan)
 		plancodec.NormalizePlanNode(
 			int(op.Depth-uint32(depthOffset)),
@@ -287,6 +293,9 @@ func NormalizeFlatPlan(flat *FlatPhysicalPlan) (normalized string, digest *parse
 		)
 	}
 	normalized = d.buf.String()
+	if len(normalized) == 0 {
+		return "", parser.NewDigest(nil)
+	}
 	_, err := d.hasher.Write(d.buf.Bytes())
 	if err != nil {
 		panic(err)

planner/core/flat_plan.go

@@ -352,6 +352,7 @@ func (f *FlatPhysicalPlan) flattenRecursively(p Plan, info *operatorCtx, target
 			target, childIdx = f.flattenRecursively(plan.SelectPlan, childCtx, target)
 			childIdxs = append(childIdxs, childIdx)
 		}
+		target, childIdxs = f.flattenForeignKeyChecksAndCascades(childCtx, target, childIdxs, plan.FKChecks, plan.FKCascades)
 	case *Update:
 		if plan.SelectPlan != nil {
 			childCtx.isRoot = true
@@ -360,6 +361,12 @@ func (f *FlatPhysicalPlan) flattenRecursively(p Plan, info *operatorCtx, target
 			target, childIdx = f.flattenRecursively(plan.SelectPlan, childCtx, target)
 			childIdxs = append(childIdxs, childIdx)
 		}
+		for _, fkChecks := range plan.FKChecks {
+			target, childIdxs = f.flattenForeignKeyChecksAndCascades(childCtx, target, childIdxs, fkChecks, nil)
+		}
+		for _, fkCascades := range plan.FKCascades {
+			target, childIdxs = f.flattenForeignKeyChecksAndCascades(childCtx, target, childIdxs, nil, fkCascades)
+		}
 	case *Delete:
 		if plan.SelectPlan != nil {
 			childCtx.isRoot = true
@@ -368,6 +375,12 @@ func (f *FlatPhysicalPlan) flattenRecursively(p Plan, info *operatorCtx, target
 			target, childIdx = f.flattenRecursively(plan.SelectPlan, childCtx, target)
 			childIdxs = append(childIdxs, childIdx)
 		}
+		for _, fkChecks := range plan.FKChecks {
+			target, childIdxs = f.flattenForeignKeyChecksAndCascades(childCtx, target, childIdxs, fkChecks, nil)
+		}
+		for _, fkCascades := range plan.FKCascades {
+			target, childIdxs = f.flattenForeignKeyChecksAndCascades(childCtx, target, childIdxs, nil, fkCascades)
+		}
 	case *Execute:
 		f.InExecute = true
 		if plan.Plan != nil {
@@ -401,6 +414,25 @@ func (f *FlatPhysicalPlan) flattenRecursively(p Plan, info *operatorCtx, target
 	return target, idx
 }
 
+func (f *FlatPhysicalPlan) flattenForeignKeyChecksAndCascades(childCtx *operatorCtx, target FlatPlanTree, childIdxs []int, fkChecks []*FKCheck, fkCascades []*FKCascade) (FlatPlanTree, []int) {
+	var childIdx int
+	for _, fkCheck := range fkChecks {
+		childCtx.isRoot = true
+		childCtx.label = Empty
+		childCtx.isLastChild = true
+		target, childIdx = f.flattenRecursively(fkCheck, childCtx, target)
+		childIdxs = append(childIdxs, childIdx)
+	}
+	for _, fkCascade := range fkCascades {
+		childCtx.isRoot = true
+		childCtx.label = Empty
+		childCtx.isLastChild = true
+		target, childIdx = f.flattenRecursively(fkCascade, childCtx, target)
+		childIdxs = append(childIdxs, childIdx)
+	}
+	return target, childIdxs
+}
+
 func (f *FlatPhysicalPlan) flattenCTERecursively(cteDef *CTEDefinition, info *operatorCtx, target FlatPlanTree) FlatPlanTree {
 	flat := f.flattenSingle(cteDef, info)
 	if flat != nil {