Add index hint support

engine.go

@@ -1433,3 +1433,10 @@ func (engine *Engine) Transaction(f func(*Session) (interface{}, error)) (interf
 
 	return result, nil
 }
+
+func (engine *Engine) IndexHint(op, indexerOrColName string) *Session {
+	session := engine.NewSession()
+	session.isAutoClose = true
+	session.statement.LastError = session.statement.IndexHint(op, indexerOrColName)
+	return session
+}

internal/statements/index.go

@@ -0,0 +1,49 @@
+// Copyright 2023 The Xorm Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package statements
+
+import (
+	"strings"
+
+	"xorm.io/builder"
+)
+
+type ErrInvalidIndexHintOperator struct {
+	Op string
+}
+
+func (e ErrInvalidIndexHintOperator) Error() string {
+	return "invalid index hint operator: " + e.Op
+}
+
+func (statement *Statement) IndexHint(op, indexName string) error {
+	op = strings.ToUpper(op)
+	statement.indexHints = append(statement.indexHints, indexHint{
+		op:        op,
+		indexName: indexName,
+	})
+	return nil
+}
+
+func (statement *Statement) writeIndexHints(w *builder.BytesWriter) error {
+	switch statement.dialect.URI().DBType {
+	case "mysql":
+		return statement.writeIndexHintsMySQL(w)
+	default:
+		return ErrNotImplemented
+	}
+}
+
+func (statement *Statement) writeIndexHintsMySQL(w *builder.BytesWriter) error {
+	for _, hint := range statement.indexHints {
+		if hint.op != "USE" && hint.op != "FORCE" && hint.op != "IGNORE" {
+			return ErrInvalidIndexHintOperator{Op: hint.op}
+		}
+		if err := statement.writeStrings(hint.op, " INDEX(", hint.indexName, ")")(w); err != nil {
+			return err
+		}
+	}
+	return nil
+}

internal/statements/query.go

@@ -254,6 +254,7 @@ func (statement *Statement) writeSelect(buf *builder.BytesWriter, columnStr stri
 	return statement.writeMultiple(buf,
 		statement.writeSelectColumns(columnStr),
 		statement.writeFrom,
+		statement.writeIndexHints,
 		statement.writeWhere,
 		statement.writeGroupBy,
 		statement.writeHaving,

internal/statements/statement.go

@@ -41,6 +41,11 @@ type join struct {
 	args      []interface{}
 }
 
+type indexHint struct {
+	op        string
+	indexName string
+}
+
 // Statement save all the sql info for executing SQL
 type Statement struct {
 	RefTable        *schemas.Table
@@ -84,6 +89,7 @@ type Statement struct {
 	BufferSize      int
 	Context         contexts.ContextCache
 	LastError       error
+	indexHints      []indexHint
 }
 
 // NewStatement creates a new statement

session_schema.go

@@ -311,3 +311,8 @@ func (session *Session) Import(r io.Reader) ([]sql.Result, error) {
 
 	return results, lastError
 }
+
+func (session *Session) IndexHint(op, indexerOrColName string) *Session {
+	session.statement.IndexHint(op, indexerOrColName)
+	return session
+}

tests/session_test.go

@@ -62,3 +62,14 @@ func TestEnableSessionId(t *testing.T) {
 	_, err := testEngine.Table("userinfo").MustLogSQL(true).Get(new(Userinfo))
 	assert.NoError(t, err)
 }
+
+func TestIndexHint(t *testing.T) {
+	assert.NoError(t, PrepareEngine())
+	assertSync(t, new(Userinfo))
+	if testEngine.Dialect().URI().DBType != "mysql" {
+		return
+	}
+
+	_, err := testEngine.Table("userinfo").IndexHint("USE", "idx1").Get(new(Userinfo))
+	assert.NoError(t, err)
+}