addressed some review comments

Author: angelamayxie

sql/analyzer/apply_foreign_keys.go

@@ -122,8 +122,6 @@ func applyForeignKeysToNodes(ctx *sql.Context, a *Analyzer, n sql.Node, cache *f
 		if plan.IsEmptyTable(n.Child) {
 			return n, transform.SameTree, nil
 		}
-		// TODO: UPDATE JOIN can update multiple tables. Because updatableJoinTable does not implement
-		//       sql.ForeignKeyTable, we do not currenly support FK checks for UPDATE JOIN statements.
 		updateDest, err := plan.GetUpdatable(n.Child)
 		if err != nil {
 			return nil, transform.SameTree, err
@@ -459,6 +457,8 @@ func getForeignKeyRefActions(ctx *sql.Context, a *Analyzer, tbl sql.ForeignKeyTa
 	return fkEditor, nil
 }
 
+// getForeignKeyHandlerFromUpdateDestination creates a ForeignKeyHandler from a given UpdatableTable. It's used in
+// applying foreign keys to Update nodes
 func getForeignKeyHandlerFromUpdateDestination(updateDest sql.UpdatableTable, ctx *sql.Context, a *Analyzer,
 	cache *foreignKeyCache, fkChain foreignKeyChain, originalNode sql.Node) (*plan.ForeignKeyHandler, error) {
 	fkTbl, ok := updateDest.(sql.ForeignKeyTable)

sql/analyzer/assign_update_join.go

@@ -34,6 +34,7 @@ func modifyUpdateExprsForJoin(ctx *sql.Context, a *Analyzer, n sql.Node, scope *
 			return n, transform.SameTree, nil
 		}
 
+		n.IsJoin = true
 		updateTargets, err := getUpdateTargetsByTable(us, jn)
 		if err != nil {
 			return nil, transform.SameTree, err

sql/plan/update_join.go

@@ -21,14 +21,14 @@ import (
 )
 
 type UpdateJoin struct {
-	UpdateTargets map[string]sql.Node
+	updateTargets map[string]sql.Node
 	UnaryNode
 }
 
 // NewUpdateJoin returns a new *UpdateJoin node.
 func NewUpdateJoin(updateTargets map[string]sql.Node, child sql.Node) *UpdateJoin {
 	return &UpdateJoin{
-		UpdateTargets: updateTargets,
+		updateTargets: updateTargets,
 		UnaryNode:     UnaryNode{Child: child},
 	}
 }
@@ -55,7 +55,7 @@ func (u *UpdateJoin) DebugString() string {
 // GetUpdatable returns an updateJoinTable which implements sql.UpdatableTable.
 func (u *UpdateJoin) GetUpdatable() sql.UpdatableTable {
 	return &UpdatableJoinTable{
-		UpdateTargets: u.UpdateTargets,
+		UpdateTargets: u.updateTargets,
 		joinNode:      u.Child.(*UpdateSource).Child,
 	}
 }
@@ -66,7 +66,7 @@ func (u *UpdateJoin) WithChildren(children ...sql.Node) (sql.Node, error) {
 		return nil, sql.ErrInvalidChildrenNumber.New(u, len(children), 1)
 	}
 
-	return NewUpdateJoin(u.UpdateTargets, children[0]), nil
+	return NewUpdateJoin(u.updateTargets, children[0]), nil
 }
 
 func (u *UpdateJoin) IsReadOnly() bool {
@@ -79,7 +79,7 @@ func (u *UpdateJoin) CollationCoercibility(ctx *sql.Context) (collation sql.Coll
 }
 
 func (u *UpdateJoin) GetUpdaters(ctx *sql.Context) (map[string]sql.RowUpdater, error) {
-	return getUpdaters(u.UpdateTargets, ctx)
+	return getUpdaters(u.updateTargets, ctx)
 }
 
 func getUpdaters(updateTargets map[string]sql.Node, ctx *sql.Context) (map[string]sql.RowUpdater, error) {