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// Copyright 2021 The Gitea Authors. All rights reserved.
// SPDX-License-Identifier: MIT
package db
import (
"context"
"errors"
"fmt"
)
// 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, etc.
type ResourceIndex struct {
GroupID int64 `xorm:"pk"`
MaxIndex int64 `xorm:"index"`
}
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// ErrResouceOutdated represents an error when request resource outdated
ErrResouceOutdated = errors.New("resource outdated")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
)
// SyncMaxResourceIndex sync the max index with the resource
func SyncMaxResourceIndex(ctx context.Context, tableName string, groupID, maxIndex int64) (err error) {
e := GetEngine(ctx)
// try to update the max_index and acquire the write-lock for the record
res, err := e.Exec(fmt.Sprintf("UPDATE %s SET max_index=? WHERE group_id=? AND max_index<?", tableName), maxIndex, groupID, maxIndex)
if err != nil {
return err
}
affected, err := res.RowsAffected()
if err != nil {
return err
}
if affected == 0 {
// if nothing is updated, the record might not exist or might be larger, it's safe to try to insert it again and then check whether the record exists
_, errIns := e.Exec(fmt.Sprintf("INSERT INTO %s (group_id, max_index) VALUES (?, ?)", tableName), groupID, maxIndex)
var savedIdx int64
has, err := e.SQL(fmt.Sprintf("SELECT max_index FROM %s WHERE group_id=?", tableName), groupID).Get(&savedIdx)
if err != nil {
return err
}
// if the record still doesn't exist, there must be some errors (insert error)
if !has {
if errIns == nil {
return errors.New("impossible error when SyncMaxResourceIndex, insert succeeded but no record is saved")
}
return errIns
}
}
return nil
}
// GetNextResourceIndex generates a resource index, it must run in the same transaction where the resource is created
func GetNextResourceIndex(ctx context.Context, tableName string, groupID int64) (int64, error) {
e := GetEngine(ctx)
// try to update the max_index to next value, and acquire the write-lock for the record
res, err := e.Exec(fmt.Sprintf("UPDATE %s SET max_index=max_index+1 WHERE group_id=?", tableName), groupID)
if err != nil {
return 0, err
}
affected, err := res.RowsAffected()
if err != nil {
return 0, err
}
if affected == 0 {
// this slow path is only for the first time of creating a resource index
_, errIns := e.Exec(fmt.Sprintf("INSERT INTO %s (group_id, max_index) VALUES (?, 0)", tableName), groupID)
res, err = e.Exec(fmt.Sprintf("UPDATE %s SET max_index=max_index+1 WHERE group_id=?", tableName), groupID)
if err != nil {
return 0, err
}
affected, err = res.RowsAffected()
if err != nil {
return 0, err
}
// if the update still can not update any records, the record must not exist and there must be some errors (insert error)
if affected == 0 {
if errIns == nil {
return 0, errors.New("impossible error when GetNextResourceIndex, insert and update both succeeded but no record is updated")
}
return 0, errIns
}
}
// now, the new index is in database (protected by the transaction and write-lock)
var newIdx int64
has, err := e.SQL(fmt.Sprintf("SELECT max_index FROM %s WHERE group_id=?", tableName), groupID).Get(&newIdx)
if err != nil {
return 0, err
}
if !has {
return 0, errors.New("impossible error when GetNextResourceIndex, upsert succeeded but no record can be selected")
}
return newIdx, nil
}
// DeleteResourceIndex delete resource index
func DeleteResourceIndex(ctx context.Context, tableName string, groupID int64) error {
_, err := Exec(ctx, fmt.Sprintf("DELETE FROM %s WHERE group_id=?", tableName), groupID)
return err
}
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