fix: limit=0 results (#5735) (#5736)

chainable_api.go

@@ -244,7 +244,7 @@ func (db *DB) Order(value interface{}) (tx *DB) {
 // Limit specify the number of records to be retrieved
 func (db *DB) Limit(limit int) (tx *DB) {
 	tx = db.getInstance()
-	tx.Statement.AddClause(clause.Limit{Limit: limit})
+	tx.Statement.AddClause(clause.Limit{Limit: &limit})
 	return
 }
 

clause/benchmarks_test.go

@@ -29,6 +29,7 @@ func BenchmarkSelect(b *testing.B) {
 func BenchmarkComplexSelect(b *testing.B) {
 	user, _ := schema.Parse(&tests.User{}, &sync.Map{}, db.NamingStrategy)
 
+	limit10 := 10
 	for i := 0; i < b.N; i++ {
 		stmt := gorm.Statement{DB: db, Table: user.Table, Schema: user, Clauses: map[string]clause.Clause{}}
 		clauses := []clause.Interface{
@@ -43,7 +44,7 @@ func BenchmarkComplexSelect(b *testing.B) {
 				clause.Or(clause.Gt{Column: "score", Value: 100}, clause.Like{Column: "name", Value: "%linus%"}),
 			}},
 			clause.GroupBy{Columns: []clause.Column{{Name: "role"}}, Having: []clause.Expression{clause.Eq{"role", "admin"}}},
-			clause.Limit{Limit: 10, Offset: 20},
+			clause.Limit{Limit: &limit10, Offset: 20},
 			clause.OrderBy{Columns: []clause.OrderByColumn{{Column: clause.PrimaryColumn, Desc: true}}},
 		}
 

clause/limit.go

@@ -4,7 +4,7 @@ import "strconv"
 
 // Limit limit clause
 type Limit struct {
-	Limit  int
+	Limit  *int
 	Offset int
 }
 
@@ -15,12 +15,12 @@ func (limit Limit) Name() string {
 
 // Build build where clause
 func (limit Limit) Build(builder Builder) {
-	if limit.Limit > 0 {
+	if limit.Limit != nil && *limit.Limit >= 0 {
 		builder.WriteString("LIMIT ")
-		builder.WriteString(strconv.Itoa(limit.Limit))
+		builder.WriteString(strconv.Itoa(*limit.Limit))
 	}
 	if limit.Offset > 0 {
-		if limit.Limit > 0 {
+		if limit.Limit != nil && *limit.Limit >= 0 {
 			builder.WriteByte(' ')
 		}
 		builder.WriteString("OFFSET ")
@@ -33,7 +33,7 @@ func (limit Limit) MergeClause(clause *Clause) {
 	clause.Name = ""
 
 	if v, ok := clause.Expression.(Limit); ok {
-		if limit.Limit == 0 && v.Limit != 0 {
+		if (limit.Limit == nil || *limit.Limit == 0) && (v.Limit != nil && *v.Limit != 0) {
 			limit.Limit = v.Limit
 		}
 

clause/limit_test.go

@@ -8,6 +8,10 @@ import (
 )
 
 func TestLimit(t *testing.T) {
+	limit0 := 0
+	limit10 := 10
+	limit50 := 50
+	limitNeg10 := -10
 	results := []struct {
 		Clauses []clause.Interface
 		Result  string
@@ -15,11 +19,15 @@ func TestLimit(t *testing.T) {
 	}{
 		{
 			[]clause.Interface{clause.Select{}, clause.From{}, clause.Limit{
-				Limit:  10,
+				Limit:  &limit10,
 				Offset: 20,
 			}},
 			"SELECT * FROM `users` LIMIT 10 OFFSET 20", nil,
 		},
+		{
+			[]clause.Interface{clause.Select{}, clause.From{}, clause.Limit{Limit: &limit0}},
+			"SELECT * FROM `users` LIMIT 0", nil,
+		},
 		{
 			[]clause.Interface{clause.Select{}, clause.From{}, clause.Limit{Offset: 20}},
 			"SELECT * FROM `users` OFFSET 20", nil,
@@ -29,23 +37,23 @@ func TestLimit(t *testing.T) {
 			"SELECT * FROM `users` OFFSET 30", nil,
 		},
 		{
-			[]clause.Interface{clause.Select{}, clause.From{}, clause.Limit{Offset: 20}, clause.Limit{Limit: 10}},
+			[]clause.Interface{clause.Select{}, clause.From{}, clause.Limit{Offset: 20}, clause.Limit{Limit: &limit10}},
 			"SELECT * FROM `users` LIMIT 10 OFFSET 20", nil,
 		},
 		{
-			[]clause.Interface{clause.Select{}, clause.From{}, clause.Limit{Limit: 10, Offset: 20}, clause.Limit{Offset: 30}},
+			[]clause.Interface{clause.Select{}, clause.From{}, clause.Limit{Limit: &limit10, Offset: 20}, clause.Limit{Offset: 30}},
 			"SELECT * FROM `users` LIMIT 10 OFFSET 30", nil,
 		},
 		{
-			[]clause.Interface{clause.Select{}, clause.From{}, clause.Limit{Limit: 10, Offset: 20}, clause.Limit{Offset: 30}, clause.Limit{Offset: -10}},
+			[]clause.Interface{clause.Select{}, clause.From{}, clause.Limit{Limit: &limit10, Offset: 20}, clause.Limit{Offset: 30}, clause.Limit{Offset: -10}},
 			"SELECT * FROM `users` LIMIT 10", nil,
 		},
 		{
-			[]clause.Interface{clause.Select{}, clause.From{}, clause.Limit{Limit: 10, Offset: 20}, clause.Limit{Offset: 30}, clause.Limit{Limit: -10}},
+			[]clause.Interface{clause.Select{}, clause.From{}, clause.Limit{Limit: &limit10, Offset: 20}, clause.Limit{Offset: 30}, clause.Limit{Limit: &limitNeg10}},
 			"SELECT * FROM `users` OFFSET 30", nil,
 		},
 		{
-			[]clause.Interface{clause.Select{}, clause.From{}, clause.Limit{Limit: 10, Offset: 20}, clause.Limit{Offset: 30}, clause.Limit{Limit: 50}},
+			[]clause.Interface{clause.Select{}, clause.From{}, clause.Limit{Limit: &limit10, Offset: 20}, clause.Limit{Offset: 30}, clause.Limit{Limit: &limit50}},
 			"SELECT * FROM `users` LIMIT 50 OFFSET 30", nil,
 		},
 	}

finisher_api.go

@@ -185,7 +185,9 @@ func (db *DB) FindInBatches(dest interface{}, batchSize int, fc func(tx *DB, bat
 	var totalSize int
 	if c, ok := tx.Statement.Clauses["LIMIT"]; ok {
 		if limit, ok := c.Expression.(clause.Limit); ok {
-			totalSize = limit.Limit
+			if limit.Limit != nil {
+				totalSize = *limit.Limit
+			}
 
 			if totalSize > 0 && batchSize > totalSize {
 				batchSize = totalSize