Change Drupal 8 text field maximum length

If there no data, You can use field_update_field (tested on D7) Like:

$field = array(

'field_name' => 'field_name',

'type' => 'text_long',

'cardinality' => 1,

'settings' => array('max_length' => 0),

);

field_update_field($field);

But with data, you must change the database.

Change the size of a field (With data)

The 3 things that need to do:

1. Change the VARCHAR length of the value column in the field_data_{fieldname} table
2. Change the VARCHAR length of the value column in the field_revision_{fieldname} table
3. Update the configuration of the field to reflect the new max length setting

This methode work on Drupal 7 and Drupal 8.

Example:

function mymodule_change_text_field_max_length ($field_name, $new_length) {

  $field_name = 'fieldname';

  // Get the current settings

  $result = db_query('SELECT data FROM {field_config} WHERE field_name = :name', array(':name' => $field_name))->fetchField();

  // Change the settings

  $data = unserialize($result);

  $may_length = 20000;

  if ($new_length > $may_length) {

    $new_length = $may_length;

  }

  $data['settings']['max_length'] = $new_length;

  // Write settings back to the database.

  db_update('field_config')

    ->fields(array( 'data' => serialize($data), 'type' => "text_long"))

    ->condition('field_name', $field_name)

    ->execute();

  // Update the value column in both the _data and _revision tables for the field

  $new_field = array('type' => 'varchar', 'length' => $new_length);

  $col_name = $field_name . '_value';

  db_change_field("field_data_$field_name", $col_name, $col_name, $new_field);

  db_change_field("field_revision_$field_name", $col_name, $col_name, $new_field);

  // Flush the caches

  drupal_flush_all_caches();

}

function mymodule_update_8002() {

  mymodule_change_text_field_max_length('field_name', 1000);

}

Another Methode :

function mymodule_change_text_field_max_length ($field_name, $new_length) {

  $field_table = 'field_data_' . $field_name;

  $field_revision_table = 'field_revision_' . $field_name;

  $field_column = $field_name . '_value';

  $may_length = 20000;

  if($new_length>$may_length){

    $new_length = $may_length;

  }

  // Alter value field length in fields table

  db_query("ALTER TABLE `{$field_table}` CHANGE `{$field_column}` `{$field_column}` VARCHAR( {$new_length} )");

  // Alter value field length in fields revision table

  db_query("ALTER TABLE `{$field_revision_table}` CHANGE `{$field_column}` `{$field_column}` VARCHAR( {$new_length} )");

//Update field type if need

//db_query("UPDATE {field_config} SET type = 'text_long' WHERE field_name = ' $field_name '");

  // Update field config with new max length

  $result = db_query("SELECT CAST(`data` AS CHAR($may_length) CHARACTER SET utf8) FROM `field_config` WHERE field_name = '{$field_name}'");

  $config = $result->fetchField();

  $config_array = unserialize($config);

  $config_array['settings']['max_length'] = $new_length;

  $config = serialize($config_array);

  db_update('field_config')

    ->fields(array('data' => $config))

    ->condition('field_name', $field_name)

    ->execute();

}

function mymodule_update_8002() {

  mymodule_change_text_field_max_length('field_name', 1000);

}

TODO : Update Field widget to text_textarea

//'widget' => array('type' => 'text_textarea')

Another Example : http://www.pixelite.co.nz/article/convert-existing-textfield-textarea-drupal-7/