Add support for optional index hints on join tables (#255)

join.go

@@ -9,7 +9,7 @@ const (
 	full
 )
 
-func join(t joinType, table interface{}, on interface{}) Builder {
+func join(t joinType, table interface{}, on interface{}, indexHints []Builder) Builder {
 	return BuildFunc(func(d Dialect, buf Buffer) error {
 		buf.WriteString(" ")
 		switch t {
@@ -28,6 +28,12 @@ func join(t joinType, table interface{}, on interface{}) Builder {
 			buf.WriteString(placeholder)
 			buf.WriteValue(table)
 		}
+		for _, hint := range indexHints {
+			buf.WriteString(" ")
+			if err := hint.Build(d, buf); err != nil {
+				return err
+			}
+		}
 		buf.WriteString(" ON ")
 		switch on := on.(type) {
 		case string:

select.go

@@ -370,29 +370,29 @@ func (b *SelectStmt) Comment(comment string) *SelectStmt {
 
 // Join add inner-join.
 // on can be Builder or string.
-func (b *SelectStmt) Join(table, on interface{}) *SelectStmt {
-	b.JoinTable = append(b.JoinTable, join(inner, table, on))
+func (b *SelectStmt) Join(table, on interface{}, indexHints ...Builder) *SelectStmt {
+	b.JoinTable = append(b.JoinTable, join(inner, table, on, indexHints))
 	return b
 }
 
 // LeftJoin add left-join.
 // on can be Builder or string.
-func (b *SelectStmt) LeftJoin(table, on interface{}) *SelectStmt {
-	b.JoinTable = append(b.JoinTable, join(left, table, on))
+func (b *SelectStmt) LeftJoin(table, on interface{}, indexHints ...Builder) *SelectStmt {
+	b.JoinTable = append(b.JoinTable, join(left, table, on, indexHints))
 	return b
 }
 
 // RightJoin add right-join.
 // on can be Builder or string.
-func (b *SelectStmt) RightJoin(table, on interface{}) *SelectStmt {
-	b.JoinTable = append(b.JoinTable, join(right, table, on))
+func (b *SelectStmt) RightJoin(table, on interface{}, indexHints ...Builder) *SelectStmt {
+	b.JoinTable = append(b.JoinTable, join(right, table, on, indexHints))
 	return b
 }
 
 // FullJoin add full-join.
 // on can be Builder or string.
-func (b *SelectStmt) FullJoin(table, on interface{}) *SelectStmt {
-	b.JoinTable = append(b.JoinTable, join(full, table, on))
+func (b *SelectStmt) FullJoin(table, on interface{}, indexHints ...Builder) *SelectStmt {
+	b.JoinTable = append(b.JoinTable, join(full, table, on, indexHints))
 	return b
 }
 

select_test.go

@@ -4,16 +4,16 @@ import (
 	"testing"
 
 	"github.com/lib/pq"
+	"github.com/stretchr/testify/require"
 
 	"github.com/gocraft/dbr/v2/dialect"
-	"github.com/stretchr/testify/require"
 )
 
 func TestSelectStmt(t *testing.T) {
 	buf := NewBuffer()
 	builder := Select("a", "b").
 		From(Select("a").From("table")).
-		LeftJoin("table2", "table.a1 = table.a2").
+		LeftJoin("table2", "table.a1 = table.a2", UseIndex("idx_table2")).
 		Distinct().
 		Where(Eq("c", 1)).
 		GroupBy("d").
@@ -29,7 +29,7 @@ func TestSelectStmt(t *testing.T) {
 	err := builder.Build(dialect.MySQL, buf)
 	require.NoError(t, err)
 	require.Equal(t, "/* SELECT TEST */\nSELECT DISTINCT a, b FROM ? USE INDEX FOR GROUP BY(`idx_c_d`) USE INDEX(idx_e_f) IGNORE INDEX(`idx_a_b`) "+
-		"LEFT JOIN `table2` ON table.a1 = table.a2 WHERE (`c` = ?) GROUP BY d HAVING (`e` = ?) ORDER BY f ASC LIMIT 3 OFFSET 4 FOR UPDATE", buf.String())
+		"LEFT JOIN `table2` USE INDEX(`idx_table2`) ON table.a1 = table.a2 WHERE (`c` = ?) GROUP BY d HAVING (`e` = ?) ORDER BY f ASC LIMIT 3 OFFSET 4 FOR UPDATE", buf.String())
 	// two functions cannot be compared
 	require.Equal(t, 3, len(buf.Value()))
 }