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