public function SelectQuery::countQuery

Get the equivalent COUNT query of this query as a new query object.

Return value

SelectQueryInterface A new SelectQuery object with no fields or expressions besides COUNT(*).

Overrides SelectQueryInterface::countQuery

File

includes/database/select.inc, line 1447

Class

SelectQuery

Query builder for SELECT statements.

Code

public function countQuery() {
  // 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.
    foreach ($count->tables as $alias => &$table) {
      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;
  }

  $query = $this->connection->select($count);
  $query->addExpression('COUNT(*)');

  return $query;
}