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

cmd/explaintest/r/explain_foreign_key.result

@@ -0,0 +1,169 @@
+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 format = 'brief' insert into t2 values (1);
+id	estRows	task	access object	operator info
+Insert	N/A	root		N/A
+└─Foreign_Key_Check	0.00	root	table:t1	foreign_key:fk, check_exist
+explain format = 'brief' update t2 set id=id+1 where id = 1;
+id	estRows	task	access object	operator info
+Update	N/A	root		N/A
+├─Point_Get	1.00	root	table:t2	handle:1, lock
+└─Foreign_Key_Check	0.00	root	table:t1	foreign_key:fk, check_exist
+explain format = 'brief' delete from t1 where id > 1;
+id	estRows	task	access object	operator info
+Delete	N/A	root		N/A
+├─SelectLock	3333.33	root		for update 0
+│ └─TableReader	3333.33	root		data:TableRangeScan
+│   └─TableRangeScan	3333.33	cop[tikv]	table:t1	range:(1,+inf], keep order:false, stats:pseudo
+└─Foreign_Key_Cascade	0.00	root	table:t2	foreign_key:fk, on_delete:CASCADE
+explain format = 'brief' update t1 set id=id+1 where id = 1;
+id	estRows	task	access object	operator info
+Update	N/A	root		N/A
+├─Point_Get	1.00	root	table:t1	handle:1, lock
+└─Foreign_Key_Cascade	0.00	root	table:t2	foreign_key:fk, on_update:CASCADE
+explain format = 'brief' insert into t1 values (1);
+id	estRows	task	access object	operator info
+Insert	N/A	root		N/A
+explain format = 'brief' insert into t1 values (1) on duplicate key update id = 100;
+id	estRows	task	access object	operator info
+Insert	N/A	root		N/A
+└─Foreign_Key_Cascade	0.00	root	table:t2	foreign_key:fk, on_update:CASCADE
+explain format = 'brief' insert into t4 values (1);
+id	estRows	task	access object	operator info
+Insert	N/A	root		N/A
+└─Foreign_Key_Check	0.00	root	table:t3, index:idx	foreign_key:fk, check_exist
+explain format = 'brief' update t4 set id=id+1 where id = 1;
+id	estRows	task	access object	operator info
+Update	N/A	root		N/A
+├─SelectLock	10.00	root		for update 0
+│ └─IndexReader	10.00	root		index:IndexRangeScan
+│   └─IndexRangeScan	10.00	cop[tikv]	table:t4, index:idx_id(id)	range:[1,1], keep order:false, stats:pseudo
+└─Foreign_Key_Check	0.00	root	table:t3, index:idx	foreign_key:fk, check_exist
+explain format = 'brief' delete from t3 where id > 1;
+id	estRows	task	access object	operator info
+Delete	N/A	root		N/A
+├─SelectLock	3333.33	root		for update 0
+│ └─IndexReader	3333.33	root		index:IndexRangeScan
+│   └─IndexRangeScan	3333.33	cop[tikv]	table:t3, index:idx(id)	range:(1,+inf], keep order:false, stats:pseudo
+└─Foreign_Key_Check	0.00	root	table:t4, index:idx_id	foreign_key:fk, check_not_exist
+explain format = 'brief' update t3 set id=id+1 where id = 1;
+id	estRows	task	access object	operator info
+Update	N/A	root		N/A
+├─Point_Get	1.00	root	table:t3, index:idx(id)	lock
+└─Foreign_Key_Check	0.00	root	table:t4, index:idx_id	foreign_key:fk, check_not_exist
+explain format = 'brief' insert into t3 values (1);
+id	estRows	task	access object	operator info
+Insert	N/A	root		N/A
+explain format = 'brief' insert into t3 values (1) on duplicate key update id = 100;
+id	estRows	task	access object	operator info
+Insert	N/A	root		N/A
+└─Foreign_Key_Check	0.00	root	table:t4, index:idx_id	foreign_key:fk, check_not_exist
+explain format = 'brief' insert into t6 values (1,1,1);
+id	estRows	task	access object	operator info
+Insert	N/A	root		N/A
+├─Foreign_Key_Check	0.00	root	table:t5	foreign_key:fk_1, check_exist
+├─Foreign_Key_Check	0.00	root	table:t5, index:idx2	foreign_key:fk_2, check_exist
+└─Foreign_Key_Check	0.00	root	table:t5, index:idx3	foreign_key:fk_3, check_exist
+explain format = 'brief' update t6 set id=id+1, id3=id2+1 where id = 1;
+id	estRows	task	access object	operator info
+Update	N/A	root		N/A
+├─SelectLock	10.00	root		for update 0
+│ └─IndexLookUp	10.00	root		
+│   ├─IndexRangeScan(Build)	10.00	cop[tikv]	table:t6, index:idx_id(id)	range:[1,1], keep order:false, stats:pseudo
+│   └─TableRowIDScan(Probe)	10.00	cop[tikv]	table:t6	keep order:false, stats:pseudo
+├─Foreign_Key_Check	0.00	root	table:t5	foreign_key:fk_1, check_exist
+└─Foreign_Key_Check	0.00	root	table:t5, index:idx3	foreign_key:fk_3, check_exist
+explain format = 'brief' delete from t5 where id > 1;
+id	estRows	task	access object	operator info
+Delete	N/A	root		N/A
+├─SelectLock	3333.33	root		for update 0
+│ └─TableReader	3333.33	root		data:TableRangeScan
+│   └─TableRangeScan	3333.33	cop[tikv]	table:t5	range:(1,+inf], keep order:false, stats:pseudo
+├─Foreign_Key_Check	0.00	root	table:t6, index:idx_id2	foreign_key:fk_2, check_not_exist
+├─Foreign_Key_Cascade	0.00	root	table:t6, index:idx_id	foreign_key:fk_1, on_delete:CASCADE
+└─Foreign_Key_Cascade	0.00	root	table:t6, index:fk_3	foreign_key:fk_3, on_delete:CASCADE
+explain format = 'brief' update t5 set id=id+1, id2=id2+1 where id = 1;
+id	estRows	task	access object	operator info
+Update	N/A	root		N/A
+├─Point_Get	1.00	root	table:t5	handle:1, lock
+├─Foreign_Key_Cascade	0.00	root	table:t6, index:idx_id	foreign_key:fk_1, on_update:CASCADE
+└─Foreign_Key_Cascade	0.00	root	table:t6, index:idx_id2	foreign_key:fk_2, on_update:CASCADE
+explain format = 'brief' update t5 set id=id+1, id2=id2+1, id3=id3+1 where id = 1;
+id	estRows	task	access object	operator info
+Update	N/A	root		N/A
+├─Point_Get	1.00	root	table:t5	handle:1, lock
+├─Foreign_Key_Check	0.00	root	table:t6, index:fk_3	foreign_key:fk_3, check_not_exist
+├─Foreign_Key_Cascade	0.00	root	table:t6, index:idx_id	foreign_key:fk_1, on_update:CASCADE
+└─Foreign_Key_Cascade	0.00	root	table:t6, index:idx_id2	foreign_key:fk_2, on_update:CASCADE
+explain format = 'brief' insert into t5 values (1,1,1);
+id	estRows	task	access object	operator info
+Insert	N/A	root		N/A
+explain format = 'brief' insert into t5 values (1,1,1) on duplicate key update id = 100, id3=100;
+id	estRows	task	access object	operator info
+Insert	N/A	root		N/A
+├─Foreign_Key_Check	0.00	root	table:t6, index:fk_3	foreign_key:fk_3, check_not_exist
+└─Foreign_Key_Cascade	0.00	root	table:t6, index:idx_id	foreign_key:fk_1, on_update:CASCADE
+explain format = 'brief' 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	N/A	root		N/A
+├─Foreign_Key_Check	0.00	root	table:t6, index:fk_3	foreign_key:fk_3, check_not_exist
+├─Foreign_Key_Cascade	0.00	root	table:t6, index:idx_id	foreign_key:fk_1, on_update:CASCADE
+└─Foreign_Key_Cascade	0.00	root	table:t6, index:idx_id2	foreign_key:fk_2, on_update:CASCADE
+drop table if exists t1,t2,t3,t4,t5,t6;
+drop table if exists t_1,t_2,t_3,t_4;
+create table t_1 (id int key);
+create table t_2 (id int key);
+create table t_3 (id int key, id2 int, foreign key fk_1(id) references t_1(id), foreign key fk_2(id2) references t_1(id), foreign key fk_3(id) references t_2(id) ON UPDATE CASCADE ON DELETE CASCADE);
+create table t_4 (id int key, id2 int, foreign key fk_1(id) references t_2(id), foreign key fk_2(id2) references t_1(id), foreign key fk_3(id) references t_1(id) ON UPDATE CASCADE ON DELETE CASCADE);
+explain format = 'brief' update t_1,t_2 set t_1.id=2,t_2.id=2 where t_1.id=t_2.id and t_1.id=1;
+id	estRows	task	access object	operator info
+Update	N/A	root		N/A
+├─HashJoin	1.00	root		CARTESIAN inner join
+│ ├─Point_Get(Build)	1.00	root	table:t_2	handle:1
+│ └─Point_Get(Probe)	1.00	root	table:t_1	handle:1
+├─Foreign_Key_Check	0.00	root	table:t_3	foreign_key:fk_1, check_not_exist
+├─Foreign_Key_Check	0.00	root	table:t_3, index:fk_2	foreign_key:fk_2, check_not_exist
+├─Foreign_Key_Check	0.00	root	table:t_4, index:fk_2	foreign_key:fk_2, check_not_exist
+├─Foreign_Key_Check	0.00	root	table:t_4	foreign_key:fk_1, check_not_exist
+├─Foreign_Key_Cascade	0.00	root	table:t_4	foreign_key:fk_3, on_update:CASCADE
+└─Foreign_Key_Cascade	0.00	root	table:t_3	foreign_key:fk_3, on_update:CASCADE
+explain format = 'brief' delete t_1,t_2 from t_1 join t_2 where t_1.id=t_2.id and t_1.id > 0;
+id	estRows	task	access object	operator info
+Delete	N/A	root		N/A
+├─MergeJoin	4166.67	root		inner join, left key:test.t_1.id, right key:test.t_2.id
+│ ├─TableReader(Build)	3333.33	root		data:TableRangeScan
+│ │ └─TableRangeScan	3333.33	cop[tikv]	table:t_2	range:(0,+inf], keep order:true, stats:pseudo
+│ └─TableReader(Probe)	3333.33	root		data:TableRangeScan
+│   └─TableRangeScan	3333.33	cop[tikv]	table:t_1	range:(0,+inf], keep order:true, stats:pseudo
+├─Foreign_Key_Check	0.00	root	table:t_3	foreign_key:fk_1, check_not_exist
+├─Foreign_Key_Check	0.00	root	table:t_3, index:fk_2	foreign_key:fk_2, check_not_exist
+├─Foreign_Key_Check	0.00	root	table:t_4, index:fk_2	foreign_key:fk_2, check_not_exist
+├─Foreign_Key_Check	0.00	root	table:t_4	foreign_key:fk_1, check_not_exist
+├─Foreign_Key_Cascade	0.00	root	table:t_4	foreign_key:fk_3, on_delete:CASCADE
+└─Foreign_Key_Cascade	0.00	root	table:t_3	foreign_key:fk_3, on_delete:CASCADE
+set @@foreign_key_checks=0;
+explain format = 'brief' update t_1,t_2 set t_1.id=2,t_2.id=2 where t_1.id=t_2.id and t_1.id=1;
+id	estRows	task	access object	operator info
+Update	N/A	root		N/A
+└─HashJoin	1.00	root		CARTESIAN inner join
+  ├─Point_Get(Build)	1.00	root	table:t_2	handle:1
+  └─Point_Get(Probe)	1.00	root	table:t_1	handle:1
+explain format = 'brief' delete t_1,t_2 from t_1 join t_2 where t_1.id=t_2.id and t_1.id > 0;
+id	estRows	task	access object	operator info
+Delete	N/A	root		N/A
+└─MergeJoin	4166.67	root		inner join, left key:test.t_1.id, right key:test.t_2.id
+  ├─TableReader(Build)	3333.33	root		data:TableRangeScan
+  │ └─TableRangeScan	3333.33	cop[tikv]	table:t_2	range:(0,+inf], keep order:true, stats:pseudo
+  └─TableReader(Probe)	3333.33	root		data:TableRangeScan
+    └─TableRangeScan	3333.33	cop[tikv]	table:t_1	range:(0,+inf], keep order:true, stats:pseudo
+drop table if exists t_1,t_2,t_3,t_4;
+set @@global.tidb_enable_foreign_key=0;
+set @@foreign_key_checks=0;

cmd/explaintest/t/explain_foreign_key.test

@@ -0,0 +1,47 @@
+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 format = 'brief' insert into t2 values (1);
+explain format = 'brief' update t2 set id=id+1 where id = 1;
+explain format = 'brief' delete from t1 where id > 1;
+explain format = 'brief' update t1 set id=id+1 where id = 1;
+explain format = 'brief' insert into t1 values (1);
+explain format = 'brief' insert into t1 values (1) on duplicate key update id = 100;
+explain format = 'brief' insert into t4 values (1);
+explain format = 'brief' update t4 set id=id+1 where id = 1;
+explain format = 'brief' delete from t3 where id > 1;
+explain format = 'brief' update t3 set id=id+1 where id = 1;
+explain format = 'brief' insert into t3 values (1);
+explain format = 'brief' insert into t3 values (1) on duplicate key update id = 100;
+explain format = 'brief' insert into t6 values (1,1,1);
+explain format = 'brief' update t6 set id=id+1, id3=id2+1 where id = 1;
+explain format = 'brief' delete from t5 where id > 1;
+explain format = 'brief' update t5 set id=id+1, id2=id2+1 where id = 1;
+explain format = 'brief' update t5 set id=id+1, id2=id2+1, id3=id3+1 where id = 1;
+explain format = 'brief' insert into t5 values (1,1,1);
+explain format = 'brief' insert into t5 values (1,1,1) on duplicate key update id = 100, id3=100;
+explain format = 'brief' insert into t5 values (1,1,1) on duplicate key update id = 100, id2=100, id3=100;
+drop table if exists t1,t2,t3,t4,t5,t6;
+
+drop table if exists t_1,t_2,t_3,t_4;
+create table t_1 (id int key);
+create table t_2 (id int key);
+create table t_3 (id int key, id2 int, foreign key fk_1(id) references t_1(id), foreign key fk_2(id2) references t_1(id), foreign key fk_3(id) references t_2(id) ON UPDATE CASCADE ON DELETE CASCADE);
+create table t_4 (id int key, id2 int, foreign key fk_1(id) references t_2(id), foreign key fk_2(id2) references t_1(id), foreign key fk_3(id) references t_1(id) ON UPDATE CASCADE ON DELETE CASCADE);
+
+explain format = 'brief' update t_1,t_2 set t_1.id=2,t_2.id=2 where t_1.id=t_2.id and t_1.id=1;
+explain format = 'brief' delete t_1,t_2 from t_1 join t_2 where t_1.id=t_2.id and t_1.id > 0;
+set @@foreign_key_checks=0;
+explain format = 'brief' update t_1,t_2 set t_1.id=2,t_2.id=2 where t_1.id=t_2.id and t_1.id=1;
+explain format = 'brief' delete t_1,t_2 from t_1 join t_2 where t_1.id=t_2.id and t_1.id > 0;
+drop table if exists t_1,t_2,t_3,t_4;
+set @@global.tidb_enable_foreign_key=0;
+set @@foreign_key_checks=0;

planner/core/encode.go

@@ -276,6 +276,11 @@ func NormalizeFlatPlan(flat *FlatPhysicalPlan) (normalized string, digest *parse
 	d.buf.Grow(30 * len(selectPlan))
 	depthOffset := len(flat.Main) - len(selectPlan)
 	for _, op := range selectPlan {
+		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.
+			continue
+		}
 		taskTypeInfo := plancodec.EncodeTaskTypeForNormalize(op.IsRoot, op.StoreType)
 		p := op.Origin.(PhysicalPlan)
 		plancodec.NormalizePlanNode(
@@ -287,6 +292,9 @@ 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

@@ -15,6 +15,8 @@
 package core
 
 import (
+	"sort"
+
 	"github.com/pingcap/tidb/kv"
 	"github.com/pingcap/tidb/util/texttree"
 )
@@ -348,26 +350,29 @@ func (f *FlatPhysicalPlan) flattenRecursively(p Plan, info *operatorCtx, target
 		if plan.SelectPlan != nil {
 			childCtx.isRoot = true
 			childCtx.label = Empty
-			childCtx.isLastChild = true
+			childCtx.isLastChild = len(plan.FKChecks) == 0 && len(plan.FKCascades) == 0
 			target, childIdx = f.flattenRecursively(plan.SelectPlan, childCtx, target)
 			childIdxs = append(childIdxs, childIdx)
 		}
+		target, childIdxs = f.flattenForeignKeyChecksAndCascades(childCtx, target, childIdxs, plan.FKChecks, plan.FKCascades, true)
 	case *Update:
 		if plan.SelectPlan != nil {
 			childCtx.isRoot = true
 			childCtx.label = Empty
-			childCtx.isLastChild = true
+			childCtx.isLastChild = len(plan.FKChecks) == 0 && len(plan.FKCascades) == 0
 			target, childIdx = f.flattenRecursively(plan.SelectPlan, childCtx, target)
 			childIdxs = append(childIdxs, childIdx)
 		}
+		target, childIdxs = f.flattenForeignKeyChecksAndCascadesMap(childCtx, target, childIdxs, plan.FKChecks, plan.FKCascades)
 	case *Delete:
 		if plan.SelectPlan != nil {
 			childCtx.isRoot = true
 			childCtx.label = Empty
-			childCtx.isLastChild = true
+			childCtx.isLastChild = len(plan.FKChecks) == 0 && len(plan.FKCascades) == 0
 			target, childIdx = f.flattenRecursively(plan.SelectPlan, childCtx, target)
 			childIdxs = append(childIdxs, childIdx)
 		}
+		target, childIdxs = f.flattenForeignKeyChecksAndCascadesMap(childCtx, target, childIdxs, plan.FKChecks, plan.FKCascades)
 	case *Execute:
 		f.InExecute = true
 		if plan.Plan != nil {
@@ -401,6 +406,50 @@ func (f *FlatPhysicalPlan) flattenRecursively(p Plan, info *operatorCtx, target
 	return target, idx
 }
 
+func (f *FlatPhysicalPlan) flattenForeignKeyChecksAndCascadesMap(childCtx *operatorCtx, target FlatPlanTree, childIdxs []int, fkChecksMap map[int64][]*FKCheck, fkCascadesMap map[int64][]*FKCascade) (FlatPlanTree, []int) {
+	tids := make([]int64, 0, len(fkChecksMap))
+	for tid := range fkChecksMap {
+		tids = append(tids, tid)
+	}
+	// Sort by table id for explain result stable.
+	sort.Slice(tids, func(i, j int) bool {
+		return tids[i] < tids[j]
+	})
+	for i, tid := range tids {
+		target, childIdxs = f.flattenForeignKeyChecksAndCascades(childCtx, target, childIdxs, fkChecksMap[tid], nil, len(fkCascadesMap) == 0 && i == len(tids)-1)
+	}
+	tids = tids[:0]
+	for tid := range fkCascadesMap {
+		tids = append(tids, tid)
+	}
+	sort.Slice(tids, func(i, j int) bool {
+		return tids[i] < tids[j]
+	})
+	for i, tid := range tids {
+		target, childIdxs = f.flattenForeignKeyChecksAndCascades(childCtx, target, childIdxs, nil, fkCascadesMap[tid], i == len(tids)-1)
+	}
+	return target, childIdxs
+}
+
+func (f *FlatPhysicalPlan) flattenForeignKeyChecksAndCascades(childCtx *operatorCtx, target FlatPlanTree, childIdxs []int, fkChecks []*FKCheck, fkCascades []*FKCascade, isLast bool) (FlatPlanTree, []int) {
+	var childIdx int
+	for i, fkCheck := range fkChecks {
+		childCtx.isRoot = true
+		childCtx.label = Empty
+		childCtx.isLastChild = isLast && len(fkCascades) == 0 && i == len(fkChecks)-1
+		target, childIdx = f.flattenRecursively(fkCheck, childCtx, target)
+		childIdxs = append(childIdxs, childIdx)
+	}
+	for i, fkCascade := range fkCascades {
+		childCtx.isRoot = true
+		childCtx.label = Empty
+		childCtx.isLastChild = isLast && i == len(fkCascades)-1
+		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 {