public function Select::orderBy

Overrides SelectQuery::orderBy().

PostgreSQL adheres strictly to the SQL-92 standard and requires that when using DISTINCT or GROUP BY conditions, fields and expressions that are ordered on also need to be selected. This is a best effort implementation to handle the cases that can be automated by adding the field if it is not yet selected.

$query = db_select('node', 'n');
$query
  ->join('node_revision', 'nr', 'n.vid = nr.vid');
$query
  ->distinct()
  ->fields('n')
  ->orderBy('timestamp');

In this query, it is not possible (without relying on the schema) to know whether timestamp belongs to node_revisions and needs to be added or belongs to node and is already selected. Queries like this will need to be corrected in the original query by adding an explicit call to SelectQuery::addField() or SelectQuery::fields().

Since this has a small performance impact, both by the additional processing in this function and in the database that needs to return the additional fields, this is done as an override instead of implementing it directly in SelectQuery::orderBy().

Overrides Select::orderBy

File

drupal/core/lib/Drupal/Core/Database/Driver/pgsql/Select.php, line 54

Definition of Drupal\Core\Database\Driver\pgsql\Select

Class

Select

Namespace

Code

public function orderBy($field, $direction = 'ASC') {

  // Call parent function to order on this.
  $return = parent::orderBy($field, $direction);

  // If there is a table alias specified, split it up.
  if (strpos($field, '.') !== FALSE) {
    list($table, $table_field) = explode('.', $field);
  }

  // Figure out if the field has already been added.
  foreach ($this->fields as $existing_field) {
    if (!empty($table)) {

      // If table alias is given, check if field and table exists.
      if ($existing_field['table'] == $table && $existing_field['field'] == $table_field) {
        return $return;
      }
    }
    else {

      // If there is no table, simply check if the field exists as a field or
      // an aliased field.
      if ($existing_field['alias'] == $field) {
        return $return;
      }
    }
  }

  // Also check expression aliases.
  foreach ($this->expressions as $expression) {
    if ($expression['alias'] == $field) {
      return $return;
    }
  }

  // If a table loads all fields, it can not be added again. It would
  // result in an ambigious alias error because that field would be loaded
  // twice: Once through table_alias.* and once directly. If the field
  // actually belongs to a different table, it must be added manually.
  foreach ($this->tables as $table) {
    if (!empty($table['all_fields'])) {
      return $return;
    }
  }

  // If $field contains an characters which are not allowed in a field name
  // it is considered an expression, these can't be handeld automatically
  // either.
  if ($this->connection
    ->escapeField($field) != $field) {
    return $return;
  }

  // This is a case that can be handled automatically, add the field.
  $this
    ->addField(NULL, $field);
  return $return;
}