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Extending Drupal 7 text field character limit

Submitted by Joshua Williams on Mon, 04/30/2012 - 13:03
After getting the message, "There is data for this field in the database. The field settings can no longer be changed." while trying to extend the character limit for a text field in a Drupal 7 instance, I used the code below to increase the character limit. It modifies the relevant parts of the database to allow more characters. I ran the SQL code through a content node with the PHP Code Text Filter enabled, but it could also be run in a custom module. Of course, I took care to back up my site database first! 
<?php
$field_to_update = 'field_text_field_to_extend'; //Replace with field slug
$new_chars = '500';  //Replace with extended character limit
 
$result1 = db_query('ALTER TABLE {field_data_'.$field_to_update.'} CHANGE '.$field_to_update.'_value '.$field_to_update.'_value VARCHAR('.$new_chars.')');
$result2 = db_query('ALTER TABLE {field_revision_'.$field_to_update.'} CHANGE '.$field_to_update.'_value '.$field_to_update.'_value VARCHAR('.$new_chars.')');
 
$result3 = db_query('SELECT CAST(data AS CHAR(10000) CHARACTER SET utf8) data FROM {field_config} WHERE field_name = \''.$field_to_update.'\'');
foreach ($result3 as $result) {
	$data = $result->data;
}
$data_array = unserialize($data);
$data_array['settings']['max_length'] = $new_chars;
$new_data = serialize($data_array);
 
$result4 = db_query('UPDATE {field_config} SET data = :data WHERE field_name = :field', array(':data' => $new_data, ':field' => $field_to_update));
?>