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1 | <?php |
2 | |
3 | namespace Wikimedia\Rdbms; |
4 | |
5 | use Wikimedia\Rdbms\Platform\ISQLPlatform; |
6 | |
7 | /** |
8 | * A query builder for UNION queries takes SelectQueryBuilder objects |
9 | * |
10 | * Any particular query builder object should only be used for a single database query, |
11 | * and not be reused afterwards. |
12 | * |
13 | * @since 1.41 |
14 | * @ingroup Database |
15 | */ |
16 | class UnionQueryBuilder { |
17 | /** sort the results in ascending order */ |
18 | public const SORT_ASC = 'ASC'; |
19 | |
20 | /** sort the results in descending order */ |
21 | public const SORT_DESC = 'DESC'; |
22 | |
23 | /** |
24 | * @var SelectQueryBuilder[] |
25 | */ |
26 | private $sqbs = []; |
27 | |
28 | /** @var IDatabase */ |
29 | private $db; |
30 | |
31 | /** @var bool */ |
32 | private $all = IReadableDatabase::UNION_DISTINCT; |
33 | |
34 | /** @var array */ |
35 | private $options = []; |
36 | |
37 | /** |
38 | * @var string The caller (function name) to be passed to IDatabase::query() |
39 | */ |
40 | private $caller = __CLASS__; |
41 | |
42 | /** |
43 | * To create a UnionQueryBuilder instance, use `$db->newUnionQueryBuilder()` instead. |
44 | */ |
45 | public function __construct( IDatabase $db ) { |
46 | $this->db = $db; |
47 | } |
48 | |
49 | /** |
50 | * Add a select query builder object to the list of union |
51 | * |
52 | * @return $this |
53 | */ |
54 | public function add( SelectQueryBuilder $selectQueryBuilder ) { |
55 | $this->sqbs[] = $selectQueryBuilder; |
56 | return $this; |
57 | } |
58 | |
59 | /** |
60 | * Enable UNION_ALL option, the default is UNION_DISTINCT |
61 | * |
62 | * @return $this |
63 | */ |
64 | public function all() { |
65 | $this->all = $this->db::UNION_ALL; |
66 | return $this; |
67 | } |
68 | |
69 | /** |
70 | * Set the query limit. Return at most this many rows. The rows are sorted |
71 | * and then the first rows are taken until the limit is reached. Limit |
72 | * is applied to a result set after offset. |
73 | * |
74 | * If the query builder already has a limit, the old limit will be discarded. |
75 | * This would be also ignored if the DB does not support limit in union queries. |
76 | * |
77 | * @param int $limit |
78 | * @return $this |
79 | */ |
80 | public function limit( $limit ) { |
81 | if ( !$this->db->unionSupportsOrderAndLimit() ) { |
82 | return $this; |
83 | } |
84 | $this->options['LIMIT'] = $limit; |
85 | return $this; |
86 | } |
87 | |
88 | /** |
89 | * Set the offset. Skip this many rows at the start of the result set. Offset |
90 | * with limit() can theoretically be used for paging through a result set, |
91 | * but this is discouraged for performance reasons. |
92 | * |
93 | * If the query builder already has an offset, the old offset will be discarded. |
94 | * This would be also ignored if the DB does not support offset in union queries. |
95 | * |
96 | * @param int $offset |
97 | * @return $this |
98 | */ |
99 | public function offset( $offset ) { |
100 | if ( !$this->db->unionSupportsOrderAndLimit() ) { |
101 | return $this; |
102 | } |
103 | $this->options['OFFSET'] = $offset; |
104 | return $this; |
105 | } |
106 | |
107 | /** |
108 | * Set the ORDER BY clause. If it has already been set, append the |
109 | * additional fields to it. |
110 | * |
111 | * This would be ignored if the DB does not support order by in union queries. |
112 | * |
113 | * @param string[]|string $fields The field or list of fields to order by. |
114 | * @param-taint $fields exec_sql |
115 | * @param string|null $direction self::SORT_ASC or self::SORT_DESC. |
116 | * If this is null then $fields is assumed to optionally contain ASC or DESC |
117 | * after each field name. |
118 | * @param-taint $direction exec_sql |
119 | * @return $this |
120 | */ |
121 | public function orderBy( $fields, $direction = null ) { |
122 | if ( !$this->db->unionSupportsOrderAndLimit() ) { |
123 | return $this; |
124 | } |
125 | if ( $direction === null ) { |
126 | $this->mergeOption( 'ORDER BY', $fields ); |
127 | } elseif ( is_array( $fields ) ) { |
128 | $fieldsWithDirection = []; |
129 | foreach ( $fields as $field ) { |
130 | $fieldsWithDirection[] = "$field $direction"; |
131 | } |
132 | $this->mergeOption( 'ORDER BY', $fieldsWithDirection ); |
133 | } else { |
134 | $this->mergeOption( 'ORDER BY', "$fields $direction" ); |
135 | } |
136 | return $this; |
137 | } |
138 | |
139 | /** |
140 | * Add a value to an option which may be not set or a string or array. |
141 | * |
142 | * @param string $name |
143 | * @param string|string[] $newArrayOrValue |
144 | */ |
145 | private function mergeOption( $name, $newArrayOrValue ) { |
146 | $value = isset( $this->options[$name] ) |
147 | ? (array)$this->options[$name] : []; |
148 | if ( is_array( $newArrayOrValue ) ) { |
149 | $value = array_merge( $value, $newArrayOrValue ); |
150 | } else { |
151 | $value[] = $newArrayOrValue; |
152 | } |
153 | $this->options[$name] = $value; |
154 | } |
155 | |
156 | /** |
157 | * Set the method name to be included in an SQL comment. |
158 | * |
159 | * @param string $fname |
160 | * @param-taint $fname exec_sql |
161 | * @return $this |
162 | */ |
163 | public function caller( $fname ) { |
164 | $this->caller = $fname; |
165 | return $this; |
166 | } |
167 | |
168 | /** |
169 | * Run the constructed UNION query and return all results. |
170 | * |
171 | * @return IResultWrapper |
172 | */ |
173 | public function fetchResultSet() { |
174 | $query = new Query( $this->getSQL(), ISQLPlatform::QUERY_CHANGE_NONE, 'SELECT' ); |
175 | return $this->db->query( $query, $this->caller ); |
176 | } |
177 | |
178 | /** |
179 | * Run the constructed UNION query, and return a single field extracted |
180 | * from the first result row. If there were no result rows, false is |
181 | * returned. This may only be called when only one field has been added to |
182 | * the constituent queries. |
183 | * |
184 | * @since 1.42 |
185 | * @return mixed |
186 | * @return-taint tainted |
187 | */ |
188 | public function fetchField() { |
189 | $this->limit( 1 ); |
190 | foreach ( $this->fetchResultSet() as $row ) { |
191 | $row = (array)$row; |
192 | if ( count( $row ) !== 1 ) { |
193 | throw new \UnexpectedValueException( |
194 | __METHOD__ . ' expects the query to have only one field' ); |
195 | } |
196 | return $row[ array_key_first( $row ) ]; |
197 | } |
198 | return false; |
199 | } |
200 | |
201 | /** |
202 | * Run the constructed UNION query, and extract a single field from each |
203 | * result row, returning an array containing all the values. This may only |
204 | * be called when only one field has been added to the constituent queries. |
205 | * |
206 | * @since 1.42 |
207 | * @return array |
208 | * @return-taint tainted |
209 | */ |
210 | public function fetchFieldValues() { |
211 | $values = []; |
212 | foreach ( $this->fetchResultSet() as $row ) { |
213 | $row = (array)$row; |
214 | if ( count( $row ) !== 1 ) { |
215 | throw new \UnexpectedValueException( |
216 | __METHOD__ . ' expects the query to have only one field' ); |
217 | } |
218 | $values[] = $row[ array_key_first( $row ) ]; |
219 | } |
220 | return $values; |
221 | } |
222 | |
223 | /** |
224 | * Run the constructed UNION query, and return the first result row. If |
225 | * there were no results, return false. |
226 | * |
227 | * @since 1.42 |
228 | * @return \stdClass|false |
229 | * @return-taint tainted |
230 | */ |
231 | public function fetchRow() { |
232 | $this->limit( 1 ); |
233 | foreach ( $this->fetchResultSet() as $row ) { |
234 | return $row; |
235 | } |
236 | return false; |
237 | } |
238 | |
239 | /** |
240 | * Get the SQL query string which would be used by fetchResultSet(). |
241 | * |
242 | * @since 1.42 |
243 | * @return string |
244 | */ |
245 | public function getSQL() { |
246 | $sqls = []; |
247 | foreach ( $this->sqbs as $sqb ) { |
248 | $sqls[] = $sqb->getSQL(); |
249 | } |
250 | return $this->db->unionQueries( $sqls, $this->all, $this->options ); |
251 | } |
252 | |
253 | } |