MigrateSQLMap how to instantiate if table has no primary key Guys how do you instantiate this MigrateSQLMap if my destination table has no primary key?

here's my code:

 $table_name = 'taxonomy_index';
    $this-&gt;map = new MigrateSQLMap($this-&gt;machineName,
      array('id' =&gt; array(
              'type' =&gt; 'int',
              'unsigned' =&gt; TRUE,
              'not null' =&gt; TRUE,
             )
           ),
        MigrateDestinationTable::getKeySchema()
      );


im trying to import to the taxonomy_index table in drupal which we know has no primary key.

how to make this possible?
To migrate content into Drupal taxonomy terms, use the MigrateDestinationTerm class, not MigrateDestinationTable. Here is example code

    $this-&gt;map = new MigrateSQLMap(
      $this-&gt;machineName,
      array(
        'term_id' =&gt; array(
          'type' =&gt; 'int',
          'not null' =&gt; TRUE,
          'description' =&gt; 'Term ID',
        ),
      ),
      MigrateDestinationTerm::getKeySchema()
    );