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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 models
import (
"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"`
}
// IssueIndex represents the issue index table
type IssueIndex ResourceIndex
// 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// ErrResouceOutdated represents an error when request resource outdated
ErrResouceOutdated = errors.New("resource outdated")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 = 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(e Engine, tableName string, groupID int64) error {
_, err := e.Exec(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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