Add OnConflict OnConstraint support, close #3882

clause/on_conflict.go

@@ -1,11 +1,12 @@
 package clause
 
 type OnConflict struct {
-	Columns   []Column
-	Where     Where
-	DoNothing bool
-	DoUpdates Set
-	UpdateAll bool
+	Columns      []Column
+	Where        Where
+	OnConstraint string
+	DoNothing    bool
+	DoUpdates    Set
+	UpdateAll    bool
 }
 
 func (OnConflict) Name() string {
@@ -31,6 +32,12 @@ func (onConflict OnConflict) Build(builder Builder) {
 		builder.WriteByte(' ')
 	}
 
+	if onConflict.OnConstraint != "" {
+		builder.WriteString("ON CONSTRAINT ")
+		builder.WriteString(onConflict.OnConstraint)
+		builder.WriteByte(' ')
+	}
+
 	if onConflict.DoNothing {
 		builder.WriteString("DO NOTHING")
 	} else {