Select.php 21.8 KB
Newer Older
1 2
<?php

3
namespace Drupal\Core\Database\Query;
4

5 6
use Drupal\Core\Database\Database;
use Drupal\Core\Database\Connection;
7 8 9 10


/**
 * Query builder for SELECT statements.
11 12
 *
 * @ingroup database
13 14 15
 */
class Select extends Query implements SelectInterface {

16 17
  use QueryConditionTrait;

18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47
  /**
   * The fields to SELECT.
   *
   * @var array
   */
  protected $fields = array();

  /**
   * The expressions to SELECT as virtual fields.
   *
   * @var array
   */
  protected $expressions = array();

  /**
   * The tables against which to JOIN.
   *
   * This property is a nested array. Each entry is an array representing
   * a single table against which to join. The structure of each entry is:
   *
   * array(
   *   'type' => $join_type (one of INNER, LEFT OUTER, RIGHT OUTER),
   *   'table' => $table,
   *   'alias' => $alias_of_the_table,
   *   'condition' => $condition_clause_on_which_to_join,
   *   'arguments' => $array_of_arguments_for_placeholders_in_the condition.
   *   'all_fields' => TRUE to SELECT $alias.*, FALSE or NULL otherwise.
   * )
   *
   * If $table is a string, it is taken as the name of a table. If it is
48
   * a Select query object, it is taken as a subquery.
49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73
   *
   * @var array
   */
  protected $tables = array();

  /**
   * The fields by which to order this query.
   *
   * This is an associative array. The keys are the fields to order, and the value
   * is the direction to order, either ASC or DESC.
   *
   * @var array
   */
  protected $order = array();

  /**
   * The fields by which to group.
   *
   * @var array
   */
  protected $group = array();

  /**
   * The conditional object for the HAVING clause.
   *
74
   * @var \Drupal\Core\Database\Query\Condition
75 76 77 78 79 80
   */
  protected $having;

  /**
   * Whether or not this query should be DISTINCT
   *
81
   * @var bool
82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106
   */
  protected $distinct = FALSE;

  /**
   * The range limiters for this query.
   *
   * @var array
   */
  protected $range;

  /**
   * An array whose elements specify a query to UNION, and the UNION type. The
   * 'type' key may be '', 'ALL', or 'DISTINCT' to represent a 'UNION',
   * 'UNION ALL', or 'UNION DISTINCT' statement, respectively.
   *
   * All entries in this array will be applied from front to back, with the
   * first query to union on the right of the original query, the second union
   * to the right of the first, etc.
   *
   * @var array
   */
  protected $union = array();

  /**
   * Indicates if preExecute() has already been called.
107
   * @var bool
108 109 110 111 112 113 114 115
   */
  protected $prepared = FALSE;

  /**
   * The FOR UPDATE status
   */
  protected $forUpdate = FALSE;

116 117 118 119 120 121 122 123 124 125 126 127
  /**
   * Constructs a Select object.
   *
   * @param string $table
   *   The name of the table that is being queried.
   * @param string $alias
   *   The alias for the table.
   * @param \Drupal\Core\Database\Connection $connection
   *   Database connection object.
   * @param array $options
   *   Array of query options.
   */
128 129 130
  public function __construct($table, $alias = NULL, Connection $connection, $options = array()) {
    $options['return'] = Database::RETURN_STATEMENT;
    parent::__construct($connection, $options);
131
    $conjunction = isset($options['conjunction']) ? $options['conjunction'] : 'AND';
132
    $this->condition = new Condition($conjunction);
133
    $this->having = new Condition($conjunction);
134 135 136
    $this->addJoin(NULL, $table, $alias);
  }

137 138 139
  /**
   * {@inheritdoc}
   */
140 141 142 143 144
  public function addTag($tag) {
    $this->alterTags[$tag] = 1;
    return $this;
  }

145 146 147
  /**
   * {@inheritdoc}
   */
148 149 150 151
  public function hasTag($tag) {
    return isset($this->alterTags[$tag]);
  }

152 153 154
  /**
   * {@inheritdoc}
   */
155 156 157 158
  public function hasAllTags() {
    return !(boolean)array_diff(func_get_args(), array_keys($this->alterTags));
  }

159 160 161
  /**
   * {@inheritdoc}
   */
162 163 164 165
  public function hasAnyTag() {
    return (boolean)array_intersect(func_get_args(), array_keys($this->alterTags));
  }

166 167 168
  /**
   * {@inheritdoc}
   */
169 170 171 172 173
  public function addMetaData($key, $object) {
    $this->alterMetaData[$key] = $object;
    return $this;
  }

174 175 176
  /**
   * {@inheritdoc}
   */
177 178 179 180
  public function getMetaData($key) {
    return isset($this->alterMetaData[$key]) ? $this->alterMetaData[$key] : NULL;
  }

181 182 183
  /**
   * {@inheritdoc}
   */
184 185 186 187 188
  public function arguments() {
    if (!$this->compiled()) {
      return NULL;
    }

189
    $args = $this->condition->arguments() + $this->having->arguments();
190 191 192 193 194 195 196 197 198 199 200 201 202 203 204 205 206 207 208 209 210 211 212 213 214 215

    foreach ($this->tables as $table) {
      if ($table['arguments']) {
        $args += $table['arguments'];
      }
      // If this table is a subquery, grab its arguments recursively.
      if ($table['table'] instanceof SelectInterface) {
        $args += $table['table']->arguments();
      }
    }

    foreach ($this->expressions as $expression) {
      if ($expression['arguments']) {
        $args += $expression['arguments'];
      }
    }

    // If there are any dependent queries to UNION,
    // incorporate their arguments recursively.
    foreach ($this->union as $union) {
      $args += $union['query']->arguments();
    }

    return $args;
  }

216 217 218
  /**
   * {@inheritdoc}
   */
219
  public function compile(Connection $connection, PlaceholderInterface $queryPlaceholder) {
220
    $this->condition->compile($connection, $queryPlaceholder);
221 222 223 224 225 226 227 228 229 230 231 232 233 234 235
    $this->having->compile($connection, $queryPlaceholder);

    foreach ($this->tables as $table) {
      // If this table is a subquery, compile it recursively.
      if ($table['table'] instanceof SelectInterface) {
        $table['table']->compile($connection, $queryPlaceholder);
      }
    }

    // If there are any dependent queries to UNION, compile it recursively.
    foreach ($this->union as $union) {
      $union['query']->compile($connection, $queryPlaceholder);
    }
  }

236 237 238
  /**
   * {@inheritdoc}
   */
239
  public function compiled() {
240
    if (!$this->condition->compiled() || !$this->having->compiled()) {
241 242 243 244 245 246 247 248 249 250 251 252 253 254 255 256 257 258 259 260 261
      return FALSE;
    }

    foreach ($this->tables as $table) {
      // If this table is a subquery, check its status recursively.
      if ($table['table'] instanceof SelectInterface) {
        if (!$table['table']->compiled()) {
          return FALSE;
        }
      }
    }

    foreach ($this->union as $union) {
      if (!$union['query']->compiled()) {
        return FALSE;
      }
    }

    return TRUE;
  }

262 263 264
  /**
   * {@inheritdoc}
   */
265 266 267 268 269
  public function havingCondition($field, $value = NULL, $operator = NULL) {
    $this->having->condition($field, $value, $operator);
    return $this;
  }

270
  /**
271
   * {@inheritdoc}
272
   */
273 274 275 276
  public function &havingConditions() {
    return $this->having->conditions();
  }

277
  /**
278
   * {@inheritdoc}
279
   */
280 281 282 283
  public function havingArguments() {
    return $this->having->arguments();
  }

284
  /**
285
   * {@inheritdoc}
286
   */
287 288 289 290 291
  public function having($snippet, $args = array()) {
    $this->having->where($snippet, $args);
    return $this;
  }

292
  /**
293
   * {@inheritdoc}
294
   */
295
  public function havingCompile(Connection $connection) {
296
    $this->having->compile($connection, $this);
297 298
  }

299 300 301
  /**
   * {@inheritdoc}
   */
302 303 304 305 306 307 308 309
  public function extend($extender_name) {
    $override_class = $extender_name . '_' . $this->connection->driver();
    if (class_exists($override_class)) {
      $extender_name = $override_class;
    }
    return new $extender_name($this, $this->connection);
  }

310
  /**
311
   * {@inheritdoc}
312
   */
313 314 315 316 317
  public function havingIsNull($field) {
    $this->having->isNull($field);
    return $this;
  }

318
  /**
319
   * {@inheritdoc}
320
   */
321 322 323 324 325
  public function havingIsNotNull($field) {
    $this->having->isNotNull($field);
    return $this;
  }

326
  /**
327
   * {@inheritdoc}
328
   */
329 330 331 332 333
  public function havingExists(SelectInterface $select) {
    $this->having->exists($select);
    return $this;
  }

334
  /**
335
   * {@inheritdoc}
336
   */
337 338 339 340 341
  public function havingNotExists(SelectInterface $select) {
    $this->having->notExists($select);
    return $this;
  }

342 343 344
  /**
   * {@inheritdoc}
   */
345 346 347 348 349 350 351
  public function forUpdate($set = TRUE) {
    if (isset($set)) {
      $this->forUpdate = $set;
    }
    return $this;
  }

352 353 354
  /**
   * {@inheritdoc}
   */
355 356 357 358
  public function &getFields() {
    return $this->fields;
  }

359 360 361
  /**
   * {@inheritdoc}
   */
362 363 364 365
  public function &getExpressions() {
    return $this->expressions;
  }

366 367 368
  /**
   * {@inheritdoc}
   */
369 370 371 372
  public function &getOrderBy() {
    return $this->order;
  }

373 374 375
  /**
   * {@inheritdoc}
   */
376 377 378 379
  public function &getGroupBy() {
    return $this->group;
  }

380 381 382
  /**
   * {@inheritdoc}
   */
383 384 385 386
  public function &getTables() {
    return $this->tables;
  }

387 388 389
  /**
   * {@inheritdoc}
   */
390 391 392 393
  public function &getUnion() {
    return $this->union;
  }

394 395 396 397 398 399 400
  /**
   * {@inheritdoc}
   */
  public function escapeLike($string) {
    return $this->connection->escapeLike($string);
  }

401 402 403 404 405 406 407
  /**
   * {@inheritdoc}
   */
  public function escapeField($string) {
    return $this->connection->escapeField($string);
  }

408 409 410
  /**
   * {@inheritdoc}
   */
411 412 413 414 415 416 417 418 419
  public function getArguments(PlaceholderInterface $queryPlaceholder = NULL) {
    if (!isset($queryPlaceholder)) {
      $queryPlaceholder = $this;
    }
    $this->compile($this->connection, $queryPlaceholder);
    return $this->arguments();
  }

  /**
420
   * {@inheritdoc}
421 422 423 424 425 426
   */
  public function isPrepared() {
    return $this->prepared;
  }

  /**
427
   * {@inheritdoc}
428 429 430 431 432 433 434 435 436 437 438 439 440 441 442 443 444 445
   */
  public function preExecute(SelectInterface $query = NULL) {
    // If no query object is passed in, use $this.
    if (!isset($query)) {
      $query = $this;
    }

    // Only execute this once.
    if ($query->isPrepared()) {
      return TRUE;
    }

    // Modules may alter all queries or only those having a particular tag.
    if (isset($this->alterTags)) {
      $hooks = array('query');
      foreach ($this->alterTags as $tag => $value) {
        $hooks[] = 'query_' . $tag;
      }
446
      \Drupal::moduleHandler()->alter($hooks, $query);
447 448 449 450 451 452 453 454 455 456 457 458 459 460 461 462 463 464
    }

    $this->prepared = TRUE;

    // Now also prepare any sub-queries.
    foreach ($this->tables as $table) {
      if ($table['table'] instanceof SelectInterface) {
        $table['table']->preExecute();
      }
    }

    foreach ($this->union as $union) {
      $union['query']->preExecute();
    }

    return $this->prepared;
  }

465 466 467
  /**
   * {@inheritdoc}
   */
468 469 470 471 472 473 474 475 476 477 478
  public function execute() {
    // If validation fails, simply return NULL.
    // Note that validation routines in preExecute() may throw exceptions instead.
    if (!$this->preExecute()) {
      return NULL;
    }

    $args = $this->getArguments();
    return $this->connection->query((string) $this, $args, $this->queryOptions);
  }

479 480 481
  /**
   * {@inheritdoc}
   */
482 483 484 485 486
  public function distinct($distinct = TRUE) {
    $this->distinct = $distinct;
    return $this;
  }

487 488 489
  /**
   * {@inheritdoc}
   */
490 491 492 493 494 495 496 497 498 499 500 501 502 503 504 505 506 507 508 509 510 511 512 513 514 515 516 517
  public function addField($table_alias, $field, $alias = NULL) {
    // If no alias is specified, first try the field name itself.
    if (empty($alias)) {
      $alias = $field;
    }

    // If that's already in use, try the table name and field name.
    if (!empty($this->fields[$alias])) {
      $alias = $table_alias . '_' . $field;
    }

    // If that is already used, just add a counter until we find an unused alias.
    $alias_candidate = $alias;
    $count = 2;
    while (!empty($this->fields[$alias_candidate])) {
      $alias_candidate = $alias . '_' . $count++;
    }
    $alias = $alias_candidate;

    $this->fields[$alias] = array(
      'field' => $field,
      'table' => $table_alias,
      'alias' => $alias,
    );

    return $alias;
  }

518 519 520
  /**
   * {@inheritdoc}
   */
521 522 523 524 525 526 527 528 529 530 531 532 533 534 535
  public function fields($table_alias, array $fields = array()) {
    if ($fields) {
      foreach ($fields as $field) {
        // We don't care what alias was assigned.
        $this->addField($table_alias, $field);
      }
    }
    else {
      // We want all fields from this table.
      $this->tables[$table_alias]['all_fields'] = TRUE;
    }

    return $this;
  }

536 537 538
  /**
   * {@inheritdoc}
   */
539 540 541 542 543 544 545 546 547 548 549 550 551 552 553 554 555 556 557 558 559
  public function addExpression($expression, $alias = NULL, $arguments = array()) {
    if (empty($alias)) {
      $alias = 'expression';
    }

    $alias_candidate = $alias;
    $count = 2;
    while (!empty($this->expressions[$alias_candidate])) {
      $alias_candidate = $alias . '_' . $count++;
    }
    $alias = $alias_candidate;

    $this->expressions[$alias] = array(
      'expression' => $expression,
      'alias' => $alias,
      'arguments' => $arguments,
    );

    return $alias;
  }

560 561 562
  /**
   * {@inheritdoc}
   */
563 564 565 566
  public function join($table, $alias = NULL, $condition = NULL, $arguments = array()) {
    return $this->addJoin('INNER', $table, $alias, $condition, $arguments);
  }

567 568 569
  /**
   * {@inheritdoc}
   */
570 571 572 573
  public function innerJoin($table, $alias = NULL, $condition = NULL, $arguments = array()) {
    return $this->addJoin('INNER', $table, $alias, $condition, $arguments);
  }

574 575 576
  /**
   * {@inheritdoc}
   */
577 578 579 580
  public function leftJoin($table, $alias = NULL, $condition = NULL, $arguments = array()) {
    return $this->addJoin('LEFT OUTER', $table, $alias, $condition, $arguments);
  }

581 582 583
  /**
   * {@inheritdoc}
   */
584 585 586 587
  public function rightJoin($table, $alias = NULL, $condition = NULL, $arguments = array()) {
    return $this->addJoin('RIGHT OUTER', $table, $alias, $condition, $arguments);
  }

588 589 590
  /**
   * {@inheritdoc}
   */
591 592 593 594 595 596 597 598 599 600 601 602 603 604 605 606 607 608 609 610 611 612 613 614 615 616 617 618 619 620 621 622
  public function addJoin($type, $table, $alias = NULL, $condition = NULL, $arguments = array()) {
    if (empty($alias)) {
      if ($table instanceof SelectInterface) {
        $alias = 'subquery';
      }
      else {
        $alias = $table;
      }
    }

    $alias_candidate = $alias;
    $count = 2;
    while (!empty($this->tables[$alias_candidate])) {
      $alias_candidate = $alias . '_' . $count++;
    }
    $alias = $alias_candidate;

    if (is_string($condition)) {
      $condition = str_replace('%alias', $alias, $condition);
    }

    $this->tables[$alias] = array(
      'join type' => $type,
      'table' => $table,
      'alias' => $alias,
      'condition' => $condition,
      'arguments' => $arguments,
    );

    return $alias;
  }

623 624 625
  /**
   * {@inheritdoc}
   */
626
  public function orderBy($field, $direction = 'ASC') {
627 628
    // Only allow ASC and DESC, default to ASC.
    $direction = strtoupper($direction) == 'DESC' ? 'DESC' : 'ASC';
629 630 631 632
    $this->order[$field] = $direction;
    return $this;
  }

633 634 635
  /**
   * {@inheritdoc}
   */
636 637 638 639 640 641
  public function orderRandom() {
    $alias = $this->addExpression('RAND()', 'random_field');
    $this->orderBy($alias);
    return $this;
  }

642 643 644
  /**
   * {@inheritdoc}
   */
645 646 647 648 649
  public function range($start = NULL, $length = NULL) {
    $this->range = func_num_args() ? array('start' => $start, 'length' => $length) : array();
    return $this;
  }

650 651 652
  /**
   * {@inheritdoc}
   */
653 654 655 656 657 658 659 660 661 662 663 664 665 666 667 668 669 670 671 672 673 674
  public function union(SelectInterface $query, $type = '') {
    // Handle UNION aliasing.
    switch ($type) {
      // Fold UNION DISTINCT to UNION for better cross database support.
      case 'DISTINCT':
      case '':
        $type = 'UNION';
        break;

      case 'ALL':
        $type = 'UNION ALL';
      default:
    }

    $this->union[] = array(
      'type' => $type,
      'query' => $query,
    );

    return $this;
  }

675 676 677
  /**
   * {@inheritdoc}
   */
678 679 680 681 682
  public function groupBy($field) {
    $this->group[$field] = $field;
    return $this;
  }

683
  /**
684
   * {@inheritdoc}
685
   */
686
  public function countQuery() {
687 688
    $count = $this->prepareCountQuery();

689
    $query = $this->connection->select($count, NULL, $this->queryOptions);
690 691 692 693 694 695 696 697
    $query->addExpression('COUNT(*)');

    return $query;
  }

  /**
   * Prepares a count query from the current query object.
   *
698
   * @return \Drupal\Core\Database\Query\Select
699 700 701
   *   A new query object ready to have COUNT(*) performed on it.
   */
  protected function prepareCountQuery() {
702 703 704 705 706 707 708 709 710 711 712 713 714 715 716 717 718 719 720 721 722 723 724 725 726 727 728
    // Create our new query object that we will mutate into a count query.
    $count = clone($this);

    $group_by = $count->getGroupBy();
    $having = $count->havingConditions();

    if (!$count->distinct && !isset($having[0])) {
      // When not executing a distinct query, we can zero-out existing fields
      // and expressions that are not used by a GROUP BY or HAVING. Fields
      // listed in a GROUP BY or HAVING clause need to be present in the
      // query.
      $fields =& $count->getFields();
      foreach (array_keys($fields) as $field) {
        if (empty($group_by[$field])) {
          unset($fields[$field]);
        }
      }

      $expressions =& $count->getExpressions();
      foreach (array_keys($expressions) as $field) {
        if (empty($group_by[$field])) {
          unset($expressions[$field]);
        }
      }

      // Also remove 'all_fields' statements, which are expanded into tablename.*
      // when the query is executed.
729
      foreach ($count->tables as &$table) {
730 731 732 733 734 735 736 737 738 739 740 741 742 743 744 745 746 747 748
        unset($table['all_fields']);
      }
    }

    // If we've just removed all fields from the query, make sure there is at
    // least one so that the query still runs.
    $count->addExpression('1');

    // Ordering a count query is a waste of cycles, and breaks on some
    // databases anyway.
    $orders = &$count->getOrderBy();
    $orders = array();

    if ($count->distinct && !empty($group_by)) {
      // If the query is distinct and contains a GROUP BY, we need to remove the
      // distinct because SQL99 does not support counting on distinct multiple fields.
      $count->distinct = FALSE;
    }

749 750 751 752 753
    // If there are any dependent queries to UNION, prepare each of those for
    // the count query also.
    foreach ($count->union as &$union) {
      $union['query'] = $union['query']->prepareCountQuery();
    }
754

755
    return $count;
756 757
  }

758 759 760
  /**
   * {@inheritdoc}
   */
761 762 763 764 765 766 767 768 769 770 771 772 773 774 775 776 777 778 779 780 781 782 783 784 785
  public function __toString() {
    // For convenience, we compile the query ourselves if the caller forgot
    // to do it. This allows constructs like "(string) $query" to work. When
    // the query will be executed, it will be recompiled using the proper
    // placeholder generator anyway.
    if (!$this->compiled()) {
      $this->compile($this->connection, $this);
    }

    // Create a sanitized comment string to prepend to the query.
    $comments = $this->connection->makeComment($this->comments);

    // SELECT
    $query = $comments . 'SELECT ';
    if ($this->distinct) {
      $query .= 'DISTINCT ';
    }

    // FIELDS and EXPRESSIONS
    $fields = array();
    foreach ($this->tables as $alias => $table) {
      if (!empty($table['all_fields'])) {
        $fields[] = $this->connection->escapeTable($alias) . '.*';
      }
    }
786
    foreach ($this->fields as $field) {
787 788 789 790
      // Always use the AS keyword for field aliases, as some
      // databases require it (e.g., PostgreSQL).
      $fields[] = (isset($field['table']) ? $this->connection->escapeTable($field['table']) . '.' : '') . $this->connection->escapeField($field['field']) . ' AS ' . $this->connection->escapeAlias($field['alias']);
    }
791
    foreach ($this->expressions as $expression) {
792 793 794 795 796 797 798
      $fields[] = $expression['expression'] . ' AS ' . $this->connection->escapeAlias($expression['alias']);
    }
    $query .= implode(', ', $fields);


    // FROM - We presume all queries have a FROM, as any query that doesn't won't need the query builder anyway.
    $query .= "\nFROM ";
799
    foreach ($this->tables as $table) {
800 801 802 803 804 805 806 807 808 809 810 811 812
      $query .= "\n";
      if (isset($table['join type'])) {
        $query .= $table['join type'] . ' JOIN ';
      }

      // If the table is a subquery, compile it and integrate it into this query.
      if ($table['table'] instanceof SelectInterface) {
        // Run preparation steps on this sub-query before converting to string.
        $subquery = $table['table'];
        $subquery->preExecute();
        $table_string = '(' . (string) $subquery . ')';
      }
      else {
813 814 815 816 817
        $table_string = $this->connection->escapeTable($table['table']);
        // Do not attempt prefixing cross database / schema queries.
        if (strpos($table_string, '.') === FALSE) {
          $table_string = '{' . $table_string . '}';
        }
818 819 820 821
      }

      // Don't use the AS keyword for table aliases, as some
      // databases don't support it (e.g., Oracle).
822
      $query .= $table_string . ' ' . $this->connection->escapeTable($table['alias']);
823 824 825 826 827 828 829

      if (!empty($table['condition'])) {
        $query .= ' ON ' . $table['condition'];
      }
    }

    // WHERE
830
    if (count($this->condition)) {
831
      // There is an implicit string cast on $this->condition.
832
      $query .= "\nWHERE " . $this->condition;
833 834 835 836 837 838 839 840 841 842 843 844 845 846 847 848 849 850
    }

    // GROUP BY
    if ($this->group) {
      $query .= "\nGROUP BY " . implode(', ', $this->group);
    }

    // HAVING
    if (count($this->having)) {
      // There is an implicit string cast on $this->having.
      $query .= "\nHAVING " . $this->having;
    }

    // ORDER BY
    if ($this->order) {
      $query .= "\nORDER BY ";
      $fields = array();
      foreach ($this->order as $field => $direction) {
851
        $fields[] = $this->connection->escapeField($field) . ' ' . $direction;
852 853 854 855 856 857 858 859 860 861 862 863 864 865 866 867 868 869 870 871 872 873 874 875 876 877 878 879
      }
      $query .= implode(', ', $fields);
    }

    // RANGE
    // There is no universal SQL standard for handling range or limit clauses.
    // Fortunately, all core-supported databases use the same range syntax.
    // Databases that need a different syntax can override this method and
    // do whatever alternate logic they need to.
    if (!empty($this->range)) {
      $query .= "\nLIMIT " . (int) $this->range['length'] . " OFFSET " . (int) $this->range['start'];
    }

    // UNION is a little odd, as the select queries to combine are passed into
    // this query, but syntactically they all end up on the same level.
    if ($this->union) {
      foreach ($this->union as $union) {
        $query .= ' ' . $union['type'] . ' ' . (string) $union['query'];
      }
    }

    if ($this->forUpdate) {
      $query .= ' FOR UPDATE';
    }

    return $query;
  }

880 881 882
  /**
   * {@inheritdoc}
   */
883 884 885 886 887
  public function __clone() {
    // On cloning, also clone the dependent objects. However, we do not
    // want to clone the database connection object as that would duplicate the
    // connection itself.

888
    $this->condition = clone($this->condition);
889 890 891 892 893
    $this->having = clone($this->having);
    foreach ($this->union as $key => $aggregate) {
      $this->union[$key]['query'] = clone($aggregate['query']);
    }
  }
894

895
}