dialect/sql: override column values on Updater.Set

Avoid cases like 'SET a = 1, a = 2'.

dialect/sql/builder.go

@@ -737,7 +737,7 @@ type (
 		action struct {
 			nothing bool
 			where   *Predicate
-			update  func(*UpdateSet)
+			update  []func(*UpdateSet)
 		}
 	}
 
@@ -831,11 +831,11 @@ func DoNothing() ConflictOption {
 //
 func ResolveWithIgnore() ConflictOption {
 	return func(c *conflict) {
-		c.action.update = func(u *UpdateSet) {
+		c.action.update = append(c.action.update, func(u *UpdateSet) {
 			for _, c := range u.columns {
 				u.Set(c, Expr(u.Table().C(c)))
 			}
-		}
+		})
 	}
 }
 
@@ -856,11 +856,11 @@ func ResolveWithIgnore() ConflictOption {
 //
 func ResolveWithNewValues() ConflictOption {
 	return func(c *conflict) {
-		c.action.update = func(u *UpdateSet) {
+		c.action.update = append(c.action.update, func(u *UpdateSet) {
 			for _, c := range u.columns {
 				u.SetExcluded(c)
 			}
-		}
+		})
 	}
 }
 
@@ -879,7 +879,7 @@ func ResolveWithNewValues() ConflictOption {
 //
 func ResolveWith(fn func(*UpdateSet)) ConflictOption {
 	return func(c *conflict) {
-		c.action.update = fn
+		c.action.update = append(c.action.update, fn)
 	}
 }
 
@@ -1012,7 +1012,9 @@ func (i *InsertBuilder) writeConflict() {
 	}
 	u := &UpdateSet{table: i.table, columns: i.columns, update: &UpdateBuilder{}}
 	u.update.Builder = i.Builder
-	i.conflict.action.update(u)
+	for _, f := range i.conflict.action.update {
+		f(u)
+	}
 	u.update.writeSetter()
 	if p := i.conflict.action.where; p != nil {
 		i.WriteString(" WHERE ").Join(p)
@@ -1044,6 +1046,12 @@ func (u *UpdateBuilder) Schema(name string) *UpdateBuilder {
 
 // Set sets a column to a given value.
 func (u *UpdateBuilder) Set(column string, v interface{}) *UpdateBuilder {
+	for i := range u.columns {
+		if column == u.columns[i] {
+			u.values[i] = v
+			return u
+		}
+	}
 	u.columns = append(u.columns, column)
 	u.values = append(u.values, v)
 	return u
@@ -1051,8 +1059,7 @@ func (u *UpdateBuilder) Set(column string, v interface{}) *UpdateBuilder {
 
 // Add adds a numeric value to the given column.
 func (u *UpdateBuilder) Add(column string, v interface{}) *UpdateBuilder {
-	u.columns = append(u.columns, column)
-	u.values = append(u.values, ExprFunc(func(b *Builder) {
+	return u.Set(column, ExprFunc(func(b *Builder) {
 		b.WriteString("COALESCE")
 		b.Nested(func(b *Builder) {
 			b.Ident(column).Comma().Arg(0)
@@ -1060,7 +1067,6 @@ func (u *UpdateBuilder) Add(column string, v interface{}) *UpdateBuilder {
 		b.WriteString(" + ")
 		b.Arg(v)
 	}))
-	return u
 }
 
 // SetNull sets a column as null value.