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- // Copyright 2021 The Gitea Authors. All rights reserved.
- // Use of this source code is governed by a MIT-style
- // license that can be found in the LICENSE file.
-
- package db
-
- import (
- "context"
- "errors"
- "fmt"
-
- "code.gitea.io/gitea/modules/setting"
- )
-
- // ResourceIndex represents a resource index which could be used as issue/release and others
- // We can create different tables i.e. issue_index, release_index and etc.
- type ResourceIndex struct {
- GroupID int64 `xorm:"pk"`
- MaxIndex int64 `xorm:"index"`
- }
-
- // UpsertResourceIndex the function will not return until it acquires the lock or receives an error.
- func UpsertResourceIndex(e Engine, tableName string, groupID int64) (err error) {
- // An atomic UPSERT operation (INSERT/UPDATE) is the only operation
- // that ensures that the key is actually locked.
- switch {
- case setting.Database.UseSQLite3 || setting.Database.UsePostgreSQL:
- _, err = e.Exec(fmt.Sprintf("INSERT INTO %s (group_id, max_index) "+
- "VALUES (?,1) ON CONFLICT (group_id) DO UPDATE SET max_index = %s.max_index+1",
- tableName, tableName), groupID)
- case setting.Database.UseMySQL:
- _, err = e.Exec(fmt.Sprintf("INSERT INTO %s (group_id, max_index) "+
- "VALUES (?,1) ON DUPLICATE KEY UPDATE max_index = max_index+1", tableName),
- groupID)
- case setting.Database.UseMSSQL:
- // https://weblogs.sqlteam.com/dang/2009/01/31/upsert-race-condition-with-merge/
- _, err = e.Exec(fmt.Sprintf("MERGE %s WITH (HOLDLOCK) as target "+
- "USING (SELECT ? AS group_id) AS src "+
- "ON src.group_id = target.group_id "+
- "WHEN MATCHED THEN UPDATE SET target.max_index = target.max_index+1 "+
- "WHEN NOT MATCHED THEN INSERT (group_id, max_index) "+
- "VALUES (src.group_id, 1);", tableName),
- groupID)
- default:
- return fmt.Errorf("database type not supported")
- }
- return
- }
-
- var (
- // ErrResouceOutdated represents an error when request resource outdated
- ErrResouceOutdated = errors.New("resource outdated")
- // ErrGetResourceIndexFailed represents an error when resource index retries 3 times
- ErrGetResourceIndexFailed = errors.New("get resource index failed")
- )
-
- const (
- // MaxDupIndexAttempts max retry times to create index
- MaxDupIndexAttempts = 3
- )
-
- // GetNextResourceIndex retried 3 times to generate a resource index
- func GetNextResourceIndex(tableName string, groupID int64) (int64, error) {
- for i := 0; i < MaxDupIndexAttempts; i++ {
- idx, err := getNextResourceIndex(tableName, groupID)
- if err == ErrResouceOutdated {
- continue
- }
- if err != nil {
- return 0, err
- }
- return idx, nil
- }
- return 0, ErrGetResourceIndexFailed
- }
-
- // DeleteResouceIndex delete resource index
- func DeleteResouceIndex(ctx context.Context, tableName string, groupID int64) error {
- _, err := Exec(ctx, fmt.Sprintf("DELETE FROM %s WHERE group_id=?", tableName), groupID)
- return err
- }
-
- // getNextResourceIndex return the next index
- func getNextResourceIndex(tableName string, groupID int64) (int64, error) {
- sess := x.NewSession()
- defer sess.Close()
- if err := sess.Begin(); err != nil {
- return 0, err
- }
- var preIdx int64
- _, err := sess.SQL(fmt.Sprintf("SELECT max_index FROM %s WHERE group_id = ?", tableName), groupID).Get(&preIdx)
- if err != nil {
- return 0, err
- }
-
- if err := UpsertResourceIndex(sess, tableName, groupID); err != nil {
- return 0, err
- }
-
- var curIdx int64
- has, err := sess.SQL(fmt.Sprintf("SELECT max_index FROM %s WHERE group_id = ? AND max_index=?", tableName), groupID, preIdx+1).Get(&curIdx)
- if err != nil {
- return 0, err
- }
- if !has {
- return 0, ErrResouceOutdated
- }
- if err := sess.Commit(); err != nil {
- return 0, err
- }
- return curIdx, nil
- }
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