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1 | <?php |
2 | |
3 | declare( strict_types = 1 ); |
4 | |
5 | namespace EntitySchema\DataAccess; |
6 | |
7 | use EntitySchema\Domain\Storage\IdGenerator; |
8 | use RuntimeException; |
9 | use Wikimedia\Rdbms\IDatabase; |
10 | use Wikimedia\Rdbms\ILoadBalancer; |
11 | |
12 | /** |
13 | * Unique Id generator implemented using an SQL table. |
14 | * The table needs to have the fields id_value |
15 | * |
16 | * @license GPL-2.0-or-later |
17 | * based on |
18 | * @see \Wikibase\Repo\Store\Sql\SqlIdGenerator |
19 | */ |
20 | class SqlIdGenerator implements IdGenerator { |
21 | |
22 | private ILoadBalancer $loadBalancer; |
23 | |
24 | private string $tableName; |
25 | |
26 | /** @var int[] */ |
27 | private array $idsToSkip; |
28 | |
29 | /** |
30 | * @param ILoadBalancer $loadBalancer |
31 | * @param string $tableName |
32 | * @param int[] $idsToSkip |
33 | */ |
34 | public function __construct( ILoadBalancer $loadBalancer, string $tableName, array $idsToSkip = [] ) { |
35 | $this->loadBalancer = $loadBalancer; |
36 | $this->tableName = $tableName; |
37 | $this->idsToSkip = $idsToSkip; |
38 | } |
39 | |
40 | /** |
41 | * @throws RuntimeException |
42 | */ |
43 | public function getNewId(): int { |
44 | $database = $this->loadBalancer->getConnection( DB_PRIMARY ); |
45 | |
46 | $id = $this->generateNewId( $database ); |
47 | return $id; |
48 | } |
49 | |
50 | /** |
51 | * Generates and returns a new ID. |
52 | * |
53 | * @param IDatabase $database |
54 | * @param bool $retry Retry once in case of e.g. race conditions. Defaults to true. |
55 | * |
56 | * @throws RuntimeException |
57 | * @return int |
58 | */ |
59 | private function generateNewId( IDatabase $database, bool $retry = true ): int { |
60 | $database->startAtomic( __METHOD__ ); |
61 | $currentId = $database->newSelectQueryBuilder() |
62 | ->select( [ 'id_value' ] ) |
63 | ->from( $this->tableName ) |
64 | ->forUpdate() |
65 | ->caller( __METHOD__ ) |
66 | ->fetchRow(); |
67 | |
68 | if ( is_object( $currentId ) ) { |
69 | $id = $currentId->id_value + 1; |
70 | $database->newUpdateQueryBuilder() |
71 | ->update( $this->tableName ) |
72 | ->set( [ 'id_value' => $id ] ) |
73 | ->where( $database::ALL_ROWS ) // there is only one row |
74 | ->caller( __METHOD__ )->execute(); |
75 | $success = true; // T339346 |
76 | } else { |
77 | $id = 1; |
78 | |
79 | $database->newInsertQueryBuilder() |
80 | ->insertInto( $this->tableName ) |
81 | ->row( [ |
82 | 'id_value' => $id, |
83 | ] ) |
84 | ->caller( __METHOD__ ) |
85 | ->execute(); |
86 | $success = true; // T339346 |
87 | |
88 | // Retry once, since a race condition on initial insert can cause one to fail. |
89 | // Race condition is possible due to occurrence of phantom reads is possible |
90 | // at non serializable transaction isolation level. |
91 | // @phan-suppress-next-line PhanImpossibleCondition T339346 |
92 | if ( !$success && $retry ) { |
93 | $id = $this->generateNewId( $database, false ); |
94 | $success = true; |
95 | } |
96 | } |
97 | |
98 | $database->endAtomic( __METHOD__ ); |
99 | |
100 | if ( !$success ) { |
101 | throw new RuntimeException( 'Could not generate a reliably unique ID.' ); |
102 | } |
103 | |
104 | if ( in_array( $id, $this->idsToSkip ) ) { |
105 | $id = $this->generateNewId( $database, $retry ); |
106 | } |
107 | |
108 | return $id; |
109 | } |
110 | |
111 | } |