Issue #998898 by stefan.r, Damien Tournoud, mradcliffe, mcdruid, sylus,...

   */

  protected $tableInformation = array();

  /**

   * The maximum allowed length for index, primary key and constraint names.

   *

   * Value will usually be set to a 63 chars limit but PostgreSQL allows

   * to higher this value before compiling, so we need to check for that.

   *

   * @var int

   */

  protected $maxIdentifierLength;

  /**

   * Make sure to limit identifiers according to PostgreSQL compiled in length.

   *

   * PostgreSQL allows in standard configuration identifiers no longer than 63

   * chars for table/relation names, indexes, primary keys, and constraints. So

   * we map all identifiers that are too long to drupal_base64hash_tag, where

   * tag is one of:

   *   - idx for indexes

   *   - key for constraints

   *   - pkey for primary keys

   *   - seq for sequences

   *

   * @param string $table_identifier_part

   *   The first argument used to build the identifier string. This usually

   *   refers to a table/relation name.

   * @param string $column_identifier_part

   *   The second argument used to build the identifier string. This usually

   *   refers to one or more column names.

   * @param string $tag

   *   The identifier tag. It can be one of 'idx', 'key', 'pkey' or 'seq'.

   *

   * @return string

   *   The index/constraint/pkey identifier.

   */

  protected function ensureIdentifiersLength($table_identifier_part, $column_identifier_part, $tag) {

    $info = $this->getPrefixInfo($table_identifier_part);

    $table_identifier_part = $info['table'];

    // Filters out potentially empty $column_identifier_part to ensure

    // compatibility with old naming convention (see prefixNonTable()).

    $identifiers = array_filter(array($table_identifier_part, $column_identifier_part, $tag));

    $identifierName = implode('_', $identifiers);

    // Retrieve the max identifier length which is usually 63 characters

    // but can be altered before PostgreSQL is compiled so we need to check.

    if (empty($this->maxIdentifierLength)) {

      $this->maxIdentifierLength = $this->connection->query("SHOW max_identifier_length")->fetchField();

    }

    if (strlen($identifierName) > $this->maxIdentifierLength) {

      $saveIdentifier = 'drupal_' . $this->hashBase64($identifierName) . '_' . $tag;

    }

    else {

      $saveIdentifier = $identifierName;

    }

    return $saveIdentifier;

  }

  /**

   * Fetch the list of blobs and sequences used on a table.

   *

    $sql_keys = array();

    if (isset($table['primary key']) && is_array($table['primary key'])) {

      $sql_keys[] = 'PRIMARY KEY (' . implode(', ', $table['primary key']) . ')';

      $sql_keys[] = 'CONSTRAINT ' . $this->ensureIdentifiersLength($name, '', 'pkey') . ' PRIMARY KEY (' . implode(', ', $table['primary key']) . ')';

    }

    if (isset($table['unique keys']) && is_array($table['unique keys'])) {

      foreach ($table['unique keys'] as $key_name => $key) {

        $sql_keys[] = 'CONSTRAINT ' . $this->prefixNonTable($name, $key_name, 'key') . ' UNIQUE (' . implode(', ', $key) . ')';

        $sql_keys[] = 'CONSTRAINT ' . $this->ensureIdentifiersLength($name, $key_name, 'key') . ' UNIQUE (' . implode(', ', $key) . ')';

      }

    }

    // rename them when renaming the table.

    $indexes = $this->connection->query('SELECT indexname FROM pg_indexes WHERE schemaname = :schema AND tablename = :table', array(':schema' => $old_schema, ':table' => $old_table_name));

    foreach ($indexes as $index) {

      if (preg_match('/^' . preg_quote($old_full_name) . '_(.*)$/', $index->indexname, $matches)) {

      // Get the index type by suffix, e.g. idx/key/pkey

      $index_type = substr($index->indexname, strrpos($index->indexname, '_') + 1);

      // If the index is already rewritten by ensureIdentifiersLength() to not

      // exceed the 63 chars limit of PostgreSQL, we need to take care of that.

      // Example (drupal_Gk7Su_T1jcBHVuvSPeP22_I3Ni4GrVEgTYlIYnBJkro_idx).

      if (strpos($index->indexname, 'drupal_') !== FALSE) {

        preg_match('/^drupal_(.*)_' . preg_quote($index_type) . '/', $index->indexname, $matches);

        $index_name = $matches[1];

        $this->connection->query('ALTER INDEX ' . $index->indexname . ' RENAME TO {' . $new_name . '}_' . $index_name);

      }

      else {

        if ($index_type == 'pkey') {

          // Primary keys do not have a specific name in D7.

          $index_name = '';

        }

        else {

          // Make sure to remove the suffix from index names, because

          // ensureIdentifiersLength() will add the suffix again and thus

          // would result in a wrong index name.

          preg_match('/^' . preg_quote($old_full_name) . '_(.*)_' . preg_quote($index_type) . '/', $index->indexname, $matches);

          $index_name = $matches[1];

        }

      }

      $this->connection->query('ALTER INDEX ' . $index->indexname . ' RENAME TO ' . $this->ensureIdentifiersLength($new_name, $index_name, $index_type));

    }

    // Now rename the table.

  }

  public function indexExists($table, $name) {

    // Details http://www.postgresql.org/docs/8.3/interactive/view-pg-indexes.html

    $index_name = '{' . $table . '}_' . $name . '_idx';

    // Details https://www.postgresql.org/docs/10/view-pg-indexes.html

    $index_name = $this->ensureIdentifiersLength($table, $name, 'idx');

    return (bool) $this->connection->query("SELECT 1 FROM pg_indexes WHERE indexname = '$index_name'")->fetchField();

  }

   *   The name of the constraint (typically 'pkey' or '[constraint]_key').

   */

  protected function constraintExists($table, $name) {

    $constraint_name = '{' . $table . '}_' . $name;

    // ensureIdentifiersLength() expects three parameters, thus we split our

    // constraint name in a proper name and a suffix.

    if ($name == 'pkey') {

      $suffix = $name;

      $name = '';

    }

    else {

      $pos = strrpos($name, '_');

      $suffix = substr($name, $pos + 1);

      $name = substr($name, 0, $pos);

    }

    $constraint_name = $this->ensureIdentifiersLength($table, $name, $suffix);

    return (bool) $this->connection->query("SELECT 1 FROM pg_constraint WHERE conname = '$constraint_name'")->fetchField();

  }

      throw new DatabaseSchemaObjectExistsException(t("Cannot add primary key to table @table: primary key already exists.", array('@table' => $table)));

    }

    $this->connection->query('ALTER TABLE {' . $table . '} ADD PRIMARY KEY (' . implode(',', $fields) . ')');

    $this->connection->query('ALTER TABLE {' . $table . '} ADD CONSTRAINT ' . $this->ensureIdentifiersLength($table, '', 'pkey') . ' PRIMARY KEY (' . implode(',', $fields) . ')');

  }

  public function dropPrimaryKey($table) {

      return FALSE;

    }

    $this->connection->query('ALTER TABLE {' . $table . '} DROP CONSTRAINT ' . $this->prefixNonTable($table, 'pkey'));

    $this->connection->query('ALTER TABLE {' . $table . '} DROP CONSTRAINT ' . $this->ensureIdentifiersLength($table, '', 'pkey'));

    return TRUE;

  }

      throw new DatabaseSchemaObjectExistsException(t("Cannot add unique key @name to table @table: unique key already exists.", array('@table' => $table, '@name' => $name)));

    }

    $this->connection->query('ALTER TABLE {' . $table . '} ADD CONSTRAINT "' . $this->prefixNonTable($table, $name, 'key') . '" UNIQUE (' . implode(',', $fields) . ')');

    $this->connection->query('ALTER TABLE {' . $table . '} ADD CONSTRAINT "' . $this->ensureIdentifiersLength($table, $name, 'key') . '" UNIQUE (' . implode(',', $fields) . ')');

  }

  public function dropUniqueKey($table, $name) {

      return FALSE;

    }

    $this->connection->query('ALTER TABLE {' . $table . '} DROP CONSTRAINT "' . $this->prefixNonTable($table, $name, 'key') . '"');

    $this->connection->query('ALTER TABLE {' . $table . '} DROP CONSTRAINT "' . $this->ensureIdentifiersLength($table, $name, 'key') . '"');

    return TRUE;

  }

      return FALSE;

    }

    $this->connection->query('DROP INDEX ' . $this->prefixNonTable($table, $name, 'idx'));

    $this->connection->query('DROP INDEX ' . $this->ensureIdentifiersLength($table, $name, 'idx'));

    return TRUE;

  }

  }

  protected function _createIndexSql($table, $name, $fields) {

    $query = 'CREATE INDEX "' . $this->prefixNonTable($table, $name, 'idx') . '" ON {' . $table . '} (';

    $query = 'CREATE INDEX "' . $this->ensureIdentifiersLength($table, $name, 'idx') . '" ON {' . $table . '} (';

    $query .= $this->_createKeySql($fields) . ')';

    return $query;

  }

      return $this->connection->query('SELECT obj_description(oid, ?) FROM pg_class WHERE relname = ?', array('pg_class', $info['table']))->fetchField();

    }

  }

  /**

   * Calculates a base-64 encoded, PostgreSQL-safe sha-256 hash per PostgreSQL

   * documentation: 4.1. Lexical Structure.

   *

   * @param $data

   *   String to be hashed.

   *

   * @return string

   *   A base-64 encoded sha-256 hash, with + and / replaced with _ and any =

   *   padding characters removed.

   */

  protected function hashBase64($data) {

    // Ensure lowercase as D7's pgsql driver does not quote identifiers

    // consistently, and they are therefore folded to lowercase by PostgreSQL.

    $hash = strtolower(base64_encode(hash('sha256', $data, TRUE)));

    // Modify the hash so it's safe to use in PostgreSQL identifiers.

    return strtr($hash, array('+' => '_', '/' => '_', '=' => ''));

  }

}