For debugging purposes, you can inspect the contents of the DataList object by adding the following code into the tablename_init hook function in the generated hooks/tablename.php file (replace tablename by the actual name of the concerned table):
function tablename_init(&$options, $memberInfo, &$args){ ob_start(); $xc=get_object_vars($options); ksort($xc); print_r($xc); $c=ob_get_clean(); echo "<pre>".htmlspecialchars($c)."</pre>"; return TRUE;}