in the function stringSize(), the variable $lengthReal has empty value. DB is PostgreSQL.

I found the problem:
it is in this query:

SELECT LENGTH("734558X76X2746") FROM "lime_survey_734558" ORDER BY LENGTH("734558X76X2746") DESC

For PostgreSQL, LENGTH(NULL) = NULL, so, that query puts NULL values as first rows. The result is that queryScalar() returns NULL if at least one field in column is null, and stringSize() almost always return 1 as field length.

I had to modify function in this way, by adding a WHERE condition:

function stringSize($sColumn)
{
// Find the sid
$iSurveyId = substr($sColumn, 0, strpos($sColumn, 'X'));
switch (Yii::app()->db->driverName) {
case 'sqlsrv':
case 'dblib':
case 'mssql':
$lengthWord = 'LEN';
break;
default:
$lengthWord = 'LENGTH';
}

$lengthCmd = Yii::app()->db->createCommand()
->select("{$lengthWord}(" . Yii::app()->db->quoteColumnName($sColumn) . ")")
->from("{{survey_" . $iSurveyId . "}}")
->order("{$lengthWord}(" . Yii::app()->db->quoteColumnName($sColumn) . ")  DESC")
->where(Yii::app()->db->quoteColumnName($sColumn)." IS NOT NULL ")
->limit(1);
$lengthReal = $lengthCmd->queryScalar();
// PSPP didn't accept A0 then min value to 1, see bug 13008

return max(1, (int) $lengthReal);

}

...and problem solved, at least for me: I cannot try this in other DB.

Great : can you create a pull request ?

Fix committed to 3.x-LTS branch: http://bugs.limesurvey.org/plugin.php?page=Source/view&id=31340

Fix committed to master branch: http://bugs.limesurvey.org/plugin.php?page=Source/view&id=31341

Fixed in Release 4.4.14+210322