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| 1 | +// Copyright 2021 The Gitea Authors. All rights reserved. |
| 2 | +// Use of this source code is governed by a MIT-style |
| 3 | +// license that can be found in the LICENSE file. |
| 4 | + |
| 5 | +package models |
| 6 | + |
| 7 | +import ( |
| 8 | + "errors" |
| 9 | + "fmt" |
| 10 | + |
| 11 | + "code.gitea.io/gitea/modules/setting" |
| 12 | +) |
| 13 | + |
| 14 | +// ResourceIndex represents a resource index which could be used as issue/release and others |
| 15 | +// We can create different tables i.e. issue_index, release_index and etc. |
| 16 | +type ResourceIndex struct { |
| 17 | + GroupID int64 `xorm:"unique"` |
| 18 | + MaxIndex int64 `xorm:"index"` |
| 19 | +} |
| 20 | + |
| 21 | +// IssueIndex represents the issue index table |
| 22 | +type IssueIndex ResourceIndex |
| 23 | + |
| 24 | +// upsertResourceIndex the function will not return until it acquires the lock or receives an error. |
| 25 | +func upsertResourceIndex(e Engine, tableName string, groupID int64) (err error) { |
| 26 | + // An atomic UPSERT operation (INSERT/UPDATE) is the only operation |
| 27 | + // that ensures that the key is actually locked. |
| 28 | + switch { |
| 29 | + case setting.Database.UseSQLite3 || setting.Database.UsePostgreSQL: |
| 30 | + _, err = e.Exec(fmt.Sprintf("INSERT INTO %s (group_id, max_index) "+ |
| 31 | + "VALUES (?,1) ON CONFLICT (group_id) DO UPDATE SET max_index = %s.max_index+1", |
| 32 | + tableName, tableName), groupID) |
| 33 | + case setting.Database.UseMySQL: |
| 34 | + _, err = e.Exec(fmt.Sprintf("INSERT INTO %s (group_id, max_index) "+ |
| 35 | + "VALUES (?,1) ON DUPLICATE KEY UPDATE max_index = max_index+1", tableName), |
| 36 | + groupID) |
| 37 | + case setting.Database.UseMSSQL: |
| 38 | + // https://weblogs.sqlteam.com/dang/2009/01/31/upsert-race-condition-with-merge/ |
| 39 | + _, err = e.Exec(fmt.Sprintf("MERGE %s WITH (HOLDLOCK) as target "+ |
| 40 | + "USING (SELECT ? AS group_id) AS src "+ |
| 41 | + "ON src.group_id = target.group_id "+ |
| 42 | + "WHEN MATCHED THEN UPDATE SET target.max_index = target.max_index+1 "+ |
| 43 | + "WHEN NOT MATCHED THEN INSERT (group_id, max_index) "+ |
| 44 | + "VALUES (src.group_id, 1);", tableName), |
| 45 | + groupID) |
| 46 | + default: |
| 47 | + return fmt.Errorf("database type not supported") |
| 48 | + } |
| 49 | + return |
| 50 | +} |
| 51 | + |
| 52 | +var ( |
| 53 | + // ErrResouceOutdated represents an error when request resource outdated |
| 54 | + ErrResouceOutdated = errors.New("resource outdated") |
| 55 | + // ErrGetResourceIndexFailed represents an error when resource index retries 3 times |
| 56 | + ErrGetResourceIndexFailed = errors.New("get resource index failed") |
| 57 | +) |
| 58 | + |
| 59 | +const ( |
| 60 | + maxDupIndexAttempts = 3 |
| 61 | +) |
| 62 | + |
| 63 | +// GetNextResourceIndex retried 3 times to generate a resource index |
| 64 | +func GetNextResourceIndex(tableName string, groupID int64) (int64, error) { |
| 65 | + for i := 0; i < maxDupIndexAttempts; i++ { |
| 66 | + idx, err := getNextResourceIndex(tableName, groupID) |
| 67 | + if err == ErrResouceOutdated { |
| 68 | + continue |
| 69 | + } |
| 70 | + if err != nil { |
| 71 | + return 0, err |
| 72 | + } |
| 73 | + return idx, nil |
| 74 | + } |
| 75 | + return 0, ErrGetResourceIndexFailed |
| 76 | +} |
| 77 | + |
| 78 | +// deleteResouceIndex delete resource index |
| 79 | +func deleteResouceIndex(e Engine, tableName string, groupID int64) error { |
| 80 | + _, err := e.Exec(fmt.Sprintf("DELETE FROM %s WHERE group_id=?", tableName), groupID) |
| 81 | + return err |
| 82 | +} |
| 83 | + |
| 84 | +// getNextResourceIndex return the next index |
| 85 | +func getNextResourceIndex(tableName string, groupID int64) (int64, error) { |
| 86 | + sess := x.NewSession() |
| 87 | + defer sess.Close() |
| 88 | + if err := sess.Begin(); err != nil { |
| 89 | + return 0, err |
| 90 | + } |
| 91 | + var preIdx int64 |
| 92 | + _, err := sess.SQL(fmt.Sprintf("SELECT max_index FROM %s WHERE group_id = ?", tableName), groupID).Get(&preIdx) |
| 93 | + if err != nil { |
| 94 | + return 0, err |
| 95 | + } |
| 96 | + |
| 97 | + if err := upsertResourceIndex(sess, tableName, groupID); err != nil { |
| 98 | + return 0, err |
| 99 | + } |
| 100 | + |
| 101 | + var curIdx int64 |
| 102 | + has, err := sess.SQL(fmt.Sprintf("SELECT max_index FROM %s WHERE group_id = ? AND max_index=?", tableName), groupID, preIdx+1).Get(&curIdx) |
| 103 | + if err != nil { |
| 104 | + return 0, err |
| 105 | + } |
| 106 | + if !has { |
| 107 | + return 0, ErrResouceOutdated |
| 108 | + } |
| 109 | + if err := sess.Commit(); err != nil { |
| 110 | + return 0, err |
| 111 | + } |
| 112 | + return curIdx, nil |
| 113 | +} |
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