class InsertQuery_pgsql extends InsertQuery {

  public function execute() {
    if (!$this->preExecute()) {
      return NULL;
    }

    $stmt = $this->connection->prepareQuery((string) $this);

    // Fetch the list of blobs and sequences used on that table.
    $table_information = $this->connection->schema()->queryTableInformation($this->table);

    $max_placeholder = 0;
    $blobs = array();
    $blob_count = 0;
    foreach ($this->insertValues as $insert_values) {
      foreach ($this->insertFields as $idx => $field) {
        if (isset($table_information->blob_fields[$field])) {
          $blobs[$blob_count] = fopen('php://memory', 'a');
          fwrite($blobs[$blob_count], $insert_values[$idx]);
          rewind($blobs[$blob_count]);

          $stmt->bindParam(':db_insert_placeholder_' . $max_placeholder++, $blobs[$blob_count], PDO::PARAM_LOB);

          // Pre-increment is faster in PHP than increment.
          ++$blob_count;
        }
        else {
          $stmt->bindParam(':db_insert_placeholder_' . $max_placeholder++, $insert_values[$idx]);
        }
      }
      // Check if values for a serial field has been passed.
      if (!empty($table_information->serial_fields)) {
        foreach ($table_information->serial_fields as $index => $serial_field) {
          $serial_key = array_search($serial_field, $this->insertFields);
          if ($serial_key !== FALSE) {
            $serial_value = $insert_values[$serial_key];

            // Force $last_insert_id to the specified value. This is only done
            // if $index is 0.
            if ($index == 0) {
              $last_insert_id = $serial_value;
            }
            // Set the sequence to the bigger value of either the passed
            // value or the max value of the column. It can happen that another
            // thread calls nextval() which could lead to a serial number being
            // used twice. However, trying to insert a value into a serial
            // column should only be done in very rare cases and is not thread
            // safe by definition.
            $this->connection->query("SELECT setval('" . $table_information->sequences[$index] . "', GREATEST(MAX(" . $serial_field . "), :serial_value)) FROM {" . $this->table . "}", array(':serial_value' => (int) $serial_value));
          }
        }
      }
    }
    if (!empty($this->fromQuery)) {
      // bindParam stores only a reference to the variable that is followed when
      // the statement is executed. We pass $arguments[$key] instead of $value
      // because the second argument to bindParam is passed by reference and
      // the foreach statement assigns the element to the existing reference.
      $arguments = $this->fromQuery->getArguments();
      foreach ($arguments as $key => $value) {
        $stmt->bindParam($key, $arguments[$key]);
      }
    }

    // PostgreSQL requires the table name to be specified explicitly
    // when requesting the last insert ID, so we pass that in via
    // the options array.
    $options = $this->queryOptions;

    if (!empty($table_information->sequences)) {
      $options['sequence_name'] = $table_information->sequences[0];
    }
    // If there are no sequences then we can't get a last insert id.
    elseif ($options['return'] == Database::RETURN_INSERT_ID) {
      $options['return'] = Database::RETURN_NULL;
    }
    // Only use the returned last_insert_id if it is not already set.
    if (!empty($last_insert_id)) {
      $this->connection->query($stmt, array(), $options);
    }
    else {
      $last_insert_id = $this->connection->query($stmt, array(), $options);
    }

    // Re-initialize the values array so that we can re-use this query.
    $this->insertValues = array();

    return $last_insert_id;
  }

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

    // Default fields are always placed first for consistency.
    $insert_fields = array_merge($this->defaultFields, $this->insertFields);

    // If we're selecting from a SelectQuery, finish building the query and
    // pass it back, as any remaining options are irrelevant.
    if (!empty($this->fromQuery)) {
      $insert_fields_string = $insert_fields ? ' (' . implode(', ', $insert_fields) . ') ' : ' ';
      return $comments . 'INSERT INTO {' . $this->table . '}' . $insert_fields_string . $this->fromQuery;
    }

    $query = $comments . 'INSERT INTO {' . $this->table . '} (' . implode(', ', $insert_fields) . ') VALUES ';

    $max_placeholder = 0;
    $values = array();
    if (count($this->insertValues)) {
      foreach ($this->insertValues as $insert_values) {
        $placeholders = array();

        // Default fields aren't really placeholders, but this is the most convenient
        // way to handle them.
        $placeholders = array_pad($placeholders, count($this->defaultFields), 'default');

        $new_placeholder = $max_placeholder + count($insert_values);
        for ($i = $max_placeholder; $i < $new_placeholder; ++$i) {
          $placeholders[] = ':db_insert_placeholder_' . $i;
        }
        $max_placeholder = $new_placeholder;
        $values[] = '(' . implode(', ', $placeholders) . ')';
      }
    }
    else {
      // If there are no values, then this is a default-only query. We still need to handle that.
      $placeholders = array_fill(0, count($this->defaultFields), 'default');
      $values[] = '(' . implode(', ', $placeholders) . ')';
    }

    $query .= implode(', ', $values);

    return $query;
  }
}