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| 1 | <?php |
| 2 | |
| 3 | use Wikimedia\Rdbms\IReadableDatabase; |
| 4 | |
| 5 | /** |
| 6 | * This program is free software; you can redistribute it and/or modify |
| 7 | * it under the terms of the GNU General Public License as published by |
| 8 | * the Free Software Foundation; either version 2 of the License, or |
| 9 | * (at your option) any later version. |
| 10 | * |
| 11 | * This program is distributed in the hope that it will be useful, |
| 12 | * but WITHOUT ANY WARRANTY; without even the implied warranty of |
| 13 | * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the |
| 14 | * GNU General Public License for more details. |
| 15 | * |
| 16 | * You should have received a copy of the GNU General Public License along |
| 17 | * with this program; if not, write to the Free Software Foundation, Inc., |
| 18 | * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA. |
| 19 | * http://www.gnu.org/copyleft/gpl.html |
| 20 | * |
| 21 | * @file |
| 22 | * @ingroup Maintenance |
| 23 | */ |
| 24 | |
| 25 | /** |
| 26 | * Allows iterating a large number of rows in batches transparently. |
| 27 | * By default when iterated over returns the full query result as an |
| 28 | * array of rows. Can be wrapped in RecursiveIteratorIterator to |
| 29 | * collapse those arrays into a single stream of rows queried in batches. |
| 30 | * |
| 31 | * @newable |
| 32 | */ |
| 33 | class BatchRowIterator implements RecursiveIterator { |
| 34 | |
| 35 | /** |
| 36 | * @var IReadableDatabase |
| 37 | */ |
| 38 | protected $db; |
| 39 | |
| 40 | /** |
| 41 | * @var string|array The name or names of the table to read from |
| 42 | */ |
| 43 | protected $table; |
| 44 | |
| 45 | /** |
| 46 | * @var array The name of the primary key(s) |
| 47 | */ |
| 48 | protected $primaryKey; |
| 49 | |
| 50 | /** |
| 51 | * @var int The number of rows to fetch per iteration |
| 52 | */ |
| 53 | protected $batchSize; |
| 54 | |
| 55 | /** |
| 56 | * @var array Array of strings containing SQL conditions to add to the query |
| 57 | */ |
| 58 | protected $conditions = []; |
| 59 | |
| 60 | /** |
| 61 | * @var array |
| 62 | */ |
| 63 | protected $joinConditions = []; |
| 64 | |
| 65 | /** |
| 66 | * @var array List of column names to select from the table suitable for use |
| 67 | * with IDatabase::select() |
| 68 | */ |
| 69 | protected $fetchColumns; |
| 70 | |
| 71 | /** |
| 72 | * @var string SQL Order by condition generated from $this->primaryKey |
| 73 | */ |
| 74 | protected $orderBy; |
| 75 | |
| 76 | /** |
| 77 | * @var array The current iterator value |
| 78 | */ |
| 79 | private $current = []; |
| 80 | |
| 81 | /** |
| 82 | * @var int 0-indexed number of pages fetched since self::reset() |
| 83 | */ |
| 84 | private $key = -1; |
| 85 | |
| 86 | /** |
| 87 | * @var array Additional query options |
| 88 | */ |
| 89 | protected $options = []; |
| 90 | |
| 91 | /** |
| 92 | * @var string|null For debugging which method is using this class. |
| 93 | */ |
| 94 | protected $caller; |
| 95 | |
| 96 | /** |
| 97 | * @stable to call |
| 98 | * |
| 99 | * @param IReadableDatabase $db |
| 100 | * @param string|array $table The name or names of the table to read from |
| 101 | * @param string|array $primaryKey The name or names of the primary key columns |
| 102 | * @param int $batchSize The number of rows to fetch per iteration |
| 103 | * @throws InvalidArgumentException |
| 104 | */ |
| 105 | public function __construct( IReadableDatabase $db, $table, $primaryKey, $batchSize ) { |
| 106 | if ( $batchSize < 1 ) { |
| 107 | throw new InvalidArgumentException( 'Batch size must be at least 1 row.' ); |
| 108 | } |
| 109 | $this->db = $db; |
| 110 | $this->table = $table; |
| 111 | $this->primaryKey = (array)$primaryKey; |
| 112 | $this->fetchColumns = $this->primaryKey; |
| 113 | $this->orderBy = implode( ' ASC,', $this->primaryKey ) . ' ASC'; |
| 114 | $this->batchSize = $batchSize; |
| 115 | } |
| 116 | |
| 117 | /** |
| 118 | * @param array $conditions Query conditions suitable for use with |
| 119 | * IDatabase::select |
| 120 | */ |
| 121 | public function addConditions( array $conditions ) { |
| 122 | $this->conditions = array_merge( $this->conditions, $conditions ); |
| 123 | } |
| 124 | |
| 125 | /** |
| 126 | * @param array $options Query options suitable for use with |
| 127 | * IDatabase::select |
| 128 | */ |
| 129 | public function addOptions( array $options ) { |
| 130 | $this->options = array_merge( $this->options, $options ); |
| 131 | } |
| 132 | |
| 133 | /** |
| 134 | * @param array $conditions Query join conditions suitable for use |
| 135 | * with IDatabase::select |
| 136 | */ |
| 137 | public function addJoinConditions( array $conditions ) { |
| 138 | $this->joinConditions = array_merge( $this->joinConditions, $conditions ); |
| 139 | } |
| 140 | |
| 141 | /** |
| 142 | * @param array $columns List of column names to select from the |
| 143 | * table suitable for use with IDatabase::select() |
| 144 | */ |
| 145 | public function setFetchColumns( array $columns ) { |
| 146 | // If it's not the all column selector merge in the primary keys we need |
| 147 | if ( count( $columns ) === 1 && reset( $columns ) === '*' ) { |
| 148 | $this->fetchColumns = $columns; |
| 149 | } else { |
| 150 | $this->fetchColumns = array_unique( array_merge( |
| 151 | $this->primaryKey, |
| 152 | $columns |
| 153 | ) ); |
| 154 | } |
| 155 | } |
| 156 | |
| 157 | /** |
| 158 | * Use ->setCaller( __METHOD__ ) to indicate which code is using this |
| 159 | * class. Only used in debugging output. |
| 160 | * @since 1.36 |
| 161 | * |
| 162 | * @param string $caller |
| 163 | * @return self |
| 164 | */ |
| 165 | public function setCaller( $caller ) { |
| 166 | $this->caller = $caller; |
| 167 | |
| 168 | return $this; |
| 169 | } |
| 170 | |
| 171 | /** |
| 172 | * Extracts the primary key(s) from a database row. |
| 173 | * |
| 174 | * @param stdClass $row An individual database row from this iterator |
| 175 | * @return array Map of primary key column to value within the row |
| 176 | */ |
| 177 | public function extractPrimaryKeys( $row ) { |
| 178 | $pk = []; |
| 179 | foreach ( $this->primaryKey as $alias => $column ) { |
| 180 | $name = is_numeric( $alias ) ? $column : $alias; |
| 181 | $pk[$name] = $row->{$name}; |
| 182 | } |
| 183 | return $pk; |
| 184 | } |
| 185 | |
| 186 | /** |
| 187 | * @return array The most recently fetched set of rows from the database |
| 188 | */ |
| 189 | public function current(): array { |
| 190 | return $this->current; |
| 191 | } |
| 192 | |
| 193 | /** |
| 194 | * @return int 0-indexed count of the page number fetched |
| 195 | */ |
| 196 | public function key(): int { |
| 197 | return $this->key; |
| 198 | } |
| 199 | |
| 200 | /** |
| 201 | * Reset the iterator to the beginning of the table. |
| 202 | */ |
| 203 | public function rewind(): void { |
| 204 | $this->key = -1; // self::next() will turn this into 0 |
| 205 | $this->current = []; |
| 206 | $this->next(); |
| 207 | } |
| 208 | |
| 209 | /** |
| 210 | * @return bool True when the iterator is in a valid state |
| 211 | */ |
| 212 | public function valid(): bool { |
| 213 | return (bool)$this->current; |
| 214 | } |
| 215 | |
| 216 | /** |
| 217 | * @return bool True when this result set has rows |
| 218 | */ |
| 219 | public function hasChildren(): bool { |
| 220 | return $this->current && count( $this->current ); |
| 221 | } |
| 222 | |
| 223 | /** |
| 224 | * @return null|RecursiveIterator |
| 225 | */ |
| 226 | public function getChildren(): ?RecursiveIterator { |
| 227 | return new NotRecursiveIterator( new ArrayIterator( $this->current ) ); |
| 228 | } |
| 229 | |
| 230 | /** |
| 231 | * Fetch the next set of rows from the database. |
| 232 | */ |
| 233 | public function next(): void { |
| 234 | $caller = __METHOD__; |
| 235 | if ( (string)$this->caller !== '' ) { |
| 236 | $caller .= " (for {$this->caller})"; |
| 237 | } |
| 238 | |
| 239 | $res = $this->db->select( |
| 240 | $this->table, |
| 241 | $this->fetchColumns, |
| 242 | $this->buildConditions(), |
| 243 | $caller, |
| 244 | [ |
| 245 | 'LIMIT' => $this->batchSize, |
| 246 | 'ORDER BY' => $this->orderBy, |
| 247 | ] + $this->options, |
| 248 | $this->joinConditions |
| 249 | ); |
| 250 | |
| 251 | // The iterator is converted to an array because in addition to |
| 252 | // returning it in self::current() we need to use the end value |
| 253 | // in self::buildConditions() |
| 254 | $this->current = iterator_to_array( $res ); |
| 255 | $this->key++; |
| 256 | } |
| 257 | |
| 258 | /** |
| 259 | * Uses the primary key list and the maximal result row from the |
| 260 | * previous iteration to build an SQL condition sufficient for |
| 261 | * selecting the next page of results. |
| 262 | * |
| 263 | * @return array The SQL conditions necessary to select the next set |
| 264 | * of rows in the batched query |
| 265 | */ |
| 266 | protected function buildConditions() { |
| 267 | if ( !$this->current ) { |
| 268 | return $this->conditions; |
| 269 | } |
| 270 | |
| 271 | $maxRow = end( $this->current ); |
| 272 | $maximumValues = []; |
| 273 | foreach ( $this->primaryKey as $alias => $column ) { |
| 274 | $name = is_numeric( $alias ) ? $column : $alias; |
| 275 | $maximumValues[$column] = $maxRow->$name; |
| 276 | } |
| 277 | |
| 278 | $conditions = $this->conditions; |
| 279 | $conditions[] = $this->db->buildComparison( '>', $maximumValues ); |
| 280 | |
| 281 | return $conditions; |
| 282 | } |
| 283 | } |