class Tasks

1. 9.x drupal/core/lib/Drupal/Core/Database/Install/Tasks.php \Drupal\Core\Database\Install\Tasks
2. 9.x drupal/core/lib/Drupal/Core/Database/Driver/mysql/Install/Tasks.php \Drupal\Core\Database\Driver\mysql\Install\Tasks
3. 9.x drupal/core/lib/Drupal/Core/Database/Driver/sqlite/Install/Tasks.php \Drupal\Core\Database\Driver\sqlite\Install\Tasks
4. 9.x drupal/core/lib/Drupal/Core/Database/Driver/pgsql/Install/Tasks.php \Drupal\Core\Database\Driver\pgsql\Install\Tasks

system_menu in drupal/core/modules/system/system.module

Implements hook_menu().

class Tasks extends InstallTasks {
  protected $pdoDriver = 'pgsql';
  public function __construct() {
    $this->tasks[] = array(
      'function' => 'checkEncoding',
      'arguments' => array(),
    );
    $this->tasks[] = array(
      'function' => 'checkBinaryOutput',
      'arguments' => array(),
    );
    $this->tasks[] = array(
      'function' => 'initializeDatabase',
      'arguments' => array(),
    );
  }
  public function name() {
    return st('PostgreSQL');
  }
  public function minimumVersion() {
    return '8.3';
  }

  /**
   * Check database connection and attempt to create database if the database is
   * missing.
   */
  protected function connect() {
    try {

      // This doesn't actually test the connection.
      db_set_active();

      // Now actually do a check.
      Database::getConnection();
      $this
        ->pass('Drupal can CONNECT to the database ok.');
    } catch (Exception $e) {

      // Attempt to create the database if it is not found.
      if ($e
        ->getCode() == Connection::DATABASE_NOT_FOUND) {

        // Remove the database string from connection info.
        $connection_info = Database::getConnectionInfo();
        $database = $connection_info['default']['database'];
        unset($connection_info['default']['database']);

        // In order to change the Database::$databaseInfo array, need to remove
        // the active connection, then re-add it with the new info.
        Database::removeConnection('default');
        Database::addConnectionInfo('default', 'default', $connection_info['default']);
        try {

          // Now, attempt the connection again; if it's successful, attempt to
          // create the database.
          Database::getConnection()
            ->createDatabase($database);
          Database::closeConnection();

          // Now, restore the database config.
          Database::removeConnection('default');
          $connection_info['default']['database'] = $database;
          Database::addConnectionInfo('default', 'default', $connection_info['default']);

          // Check the database connection.
          Database::getConnection();
          $this
            ->pass('Drupal can CONNECT to the database ok.');
        } catch (DatabaseNotFoundException $e) {

          // Still no dice; probably a permission issue. Raise the error to the
          // installer.
          $this
            ->fail(st('Database %database not found. The server reports the following message when attempting to create the database: %error.', array(
            '%database' => $database,
            '%error' => $e
              ->getMessage(),
          )));
        }
      }
      else {

        // Database connection failed for some other reason than the database
        // not existing.
        $this
          ->fail(st('Failed to connect to your database server. The server reports the following message: %error.<ul><li>Is the database server running?</li><li>Does the database exist, and have you entered the correct database name?</li><li>Have you entered the correct username and password?</li><li>Have you entered the correct database hostname?</li></ul>', array(
          '%error' => $e
            ->getMessage(),
        )));
        return FALSE;
      }
    }
    return TRUE;
  }

  /**
   * Check encoding is UTF8.
   */
  protected function checkEncoding() {
    try {
      if (db_query('SHOW server_encoding')
        ->fetchField() == 'UTF8') {
        $this
          ->pass(st('Database is encoded in UTF-8'));
      }
      else {
        $replacements = array(
          '%encoding' => 'UTF8',
          '%driver' => $this
            ->name(),
          '!link' => '<a href="INSTALL.pgsql.txt">INSTALL.pgsql.txt</a>',
        );
        $text = 'The %driver database must use %encoding encoding to work with Drupal.';
        $text .= 'Recreate the database with %encoding encoding. See !link for more details.';
        $this
          ->fail(st($text, $replacements));
      }
    } catch (Exception $e) {
      $this
        ->fail(st('Drupal could not determine the encoding of the database was set to UTF-8'));
    }
  }

  /**
   * Check Binary Output.
   *
   * Unserializing does not work on Postgresql 9 when bytea_output is 'hex'.
   */
  function checkBinaryOutput() {

    // PostgreSQL < 9 doesn't support bytea_output, so verify we are running
    // at least PostgreSQL 9.
    $database_connection = Database::getConnection();
    if (version_compare($database_connection
      ->version(), '9') >= 0) {
      if (!$this
        ->checkBinaryOutputSuccess()) {

        // First try to alter the database. If it fails, raise an error telling
        // the user to do it themselves.
        $connection_options = $database_connection
          ->getConnectionOptions();

        // It is safe to include the database name directly here, because this
        // code is only called when a connection to the database is already
        // established, thus the database name is guaranteed to be a correct
        // value.
        $query = "ALTER DATABASE \"" . $connection_options['database'] . "\" SET bytea_output = 'escape';";
        try {
          db_query($query);
        } catch (Exception $e) {

          // Ignore possible errors when the user doesn't have the necessary
          // privileges to ALTER the database.
        }

        // Close the database connection so that the configuration parameter
        // is applied to the current connection.
        db_close();

        // Recheck, if it fails, finally just rely on the end user to do the
        // right thing.
        if (!$this
          ->checkBinaryOutputSuccess()) {
          $replacements = array(
            '%setting' => 'bytea_output',
            '%current_value' => 'hex',
            '%needed_value' => 'escape',
            '!query' => "<code>" . $query . "</code>",
          );
          $this
            ->fail(st("The %setting setting is currently set to '%current_value', but needs to be '%needed_value'. Change this by running the following query: !query", $replacements));
        }
      }
    }
  }

  /**
   * Verify that a binary data roundtrip returns the original string.
   */
  protected function checkBinaryOutputSuccess() {
    $bytea_output = db_query("SELECT 'encoding'::bytea AS output")
      ->fetchField();
    return $bytea_output == 'encoding';
  }

  /**
   * Make PostgreSQL Drupal friendly.
   */
  function initializeDatabase() {

    // We create some functions using global names instead of prefixing them
    // like we do with table names. This is so that we don't double up if more
    // than one instance of Drupal is running on a single database. We therefore
    // avoid trying to create them again in that case.
    try {

      // Create functions.
      db_query('CREATE OR REPLACE FUNCTION "greatest"(numeric, numeric) RETURNS numeric AS
        \'SELECT CASE WHEN (($1 > $2) OR ($2 IS NULL)) THEN $1 ELSE $2 END;\'
        LANGUAGE \'sql\'');
      db_query('CREATE OR REPLACE FUNCTION "greatest"(numeric, numeric, numeric) RETURNS numeric AS
        \'SELECT greatest($1, greatest($2, $3));\'
        LANGUAGE \'sql\'');

      // Don't use {} around pg_proc table.
      if (!db_query("SELECT COUNT(*) FROM pg_proc WHERE proname = 'rand'")
        ->fetchField()) {
        db_query('CREATE OR REPLACE FUNCTION "rand"() RETURNS float AS
          \'SELECT random();\'
          LANGUAGE \'sql\'');
      }
      db_query('CREATE OR REPLACE FUNCTION "substring_index"(text, text, integer) RETURNS text AS
        \'SELECT array_to_string((string_to_array($1, $2)) [1:$3], $2);\'
        LANGUAGE \'sql\'');

      // Using || to concatenate in Drupal is not recommeneded because there are
      // database drivers for Drupal that do not support the syntax, however
      // they do support CONCAT(item1, item2) which we can replicate in
      // PostgreSQL. PostgreSQL requires the function to be defined for each
      // different argument variation the function can handle.
      db_query('CREATE OR REPLACE FUNCTION "concat"(anynonarray, anynonarray) RETURNS text AS
        \'SELECT CAST($1 AS text) || CAST($2 AS text);\'
        LANGUAGE \'sql\'
      ');
      db_query('CREATE OR REPLACE FUNCTION "concat"(text, anynonarray) RETURNS text AS
        \'SELECT $1 || CAST($2 AS text);\'
        LANGUAGE \'sql\'
      ');
      db_query('CREATE OR REPLACE FUNCTION "concat"(anynonarray, text) RETURNS text AS
        \'SELECT CAST($1 AS text) || $2;\'
        LANGUAGE \'sql\'
      ');
      db_query('CREATE OR REPLACE FUNCTION "concat"(text, text) RETURNS text AS
        \'SELECT $1 || $2;\'
        LANGUAGE \'sql\'
      ');
      $this
        ->pass(st('PostgreSQL has initialized itself.'));
    } catch (Exception $e) {
      $this
        ->fail(st('Drupal could not be correctly setup with the existing database. Revise any errors.'));
    }
  }

}