Add an auto_increment column in Magento setup scri

Question

Previously I asked how to ALTER TABLE in Magento setup script without using SQL. There, Ivan gave an excellent answer which I still refer to even now.

However I have yet to discover how to use Varien_Db_Ddl_Table::addColumn() to specify an auto_increment column. I think it has something to do with an option called identity but so far have had no luck.

Is this even possible or is that functionality incomplete?

Answer 1

I think that's something that hasn't been implemented yet.

If you look at the source to addColumn, you can see it looks for a identity/auto_increment option and sets an IDENTITY attribute on the internal column representation.

#File: lib/Varien/Db/Ddl/Table.php
if (!empty($options['identity']) || !empty($options['auto_increment'])) {
    $identity = true;
}

$upperName = strtoupper($name);
$this->_columns[$upperName] = array(
    'COLUMN_NAME'       => $name,
    'COLUMN_TYPE'       => $type,
    'COLUMN_POSITION'   => $position,
    'DATA_TYPE'         => $type,
    'DEFAULT'           => $default,
    'NULLABLE'          => $nullable,
    'LENGTH'            => $length,
    'SCALE'             => $scale,
    'PRECISION'         => $precision,
    'UNSIGNED'          => $unsigned,
    'PRIMARY'           => $primary,
    'PRIMARY_POSITION'  => $primaryPosition,
    'IDENTITY'          => $identity
);

However, if you look at the createTable method on the connection object

#File: lib/Varien/Db/Adapter/Pdo/Mysql.php
public function createTable(Varien_Db_Ddl_Table $table)
{
    $sqlFragment    = array_merge(
        $this->_getColumnsDefinition($table),
        $this->_getIndexesDefinition($table),
        $this->_getForeignKeysDefinition($table)
    );
    $tableOptions   = $this->_getOptionsDefination($table);

    $sql = sprintf("CREATE TABLE %s (\n%s\n) %s",
        $this->quoteIdentifier($table->getName()),
        implode(",\n", $sqlFragment),
        implode(" ", $tableOptions));

    return $this->query($sql);
}

you can see _getColumnsDefinition, _getIndexesDefinition, and _getForeignKeysDefinition are used to create a CREATE SQL fragment. None of these methods make any reference to identity or auto_increment, nor do they appear to generate any sql that would create an auto increment.

The only possible candidates in this class are

/**
 * Autoincrement for bind value
 *
 * @var int
 */
protected $_bindIncrement       = 0;

which is used to control the increment number for a PDO bound parameter (nothing to do with auto_increment).

There's also a mention of auto_increment here

protected function _getOptionsDefination(Varien_Db_Ddl_Table $table)
{
    $definition = array();
    $tableProps = array(
        'type'              => 'ENGINE=%s',
        'checksum'          => 'CHECKSUM=%d',
        'auto_increment'    => 'AUTO_INCREMENT=%d',
        'avg_row_length'    => 'AVG_ROW_LENGTH=%d',
        'comment'           => 'COMMENT=\'%s\'',
        'max_rows'          => 'MAX_ROWS=%d',
        'min_rows'          => 'MIN_ROWS=%d',
        'delay_key_write'   => 'DELAY_KEY_WRITE=%d',
        'row_format'        => 'row_format=%s',
        'charset'           => 'charset=%s',
        'collate'           => 'COLLATE=%s'
    );
    foreach ($tableProps as $key => $mask) {
        $v = $table->getOption($key);
        if (!is_null($v)) {
            $definition[] = sprintf($mask, $v);
        }
    }

    return $definition;
}

but this is used to process options set on the table. This auto_increment controls the table AUTO_INCREMENT options, which can be used to control which integer an AUTO_INCREMENT starts at.

Answer 2

One can create an autoincrement column like that (at least since Magento 1.6, maybe even earlier):

/** @var $table Varien_Db_Ddl_Table */
$table->addColumn( 'id', Varien_Db_Ddl_Table::TYPE_INTEGER, null, array(
    'auto_increment' => true,
    'unsigned' => true,
    'nullable' => false,
    'primary' => true,
), 'ID' );

Instead of "auto_increment", one may also use the keyword "identity".