Drupal 7
在Drupal 7中创建文本字段时，必须选择数据的最大长度。为该字段创建任何数据后，最大长度在Drupal字段设置中将变为不变。
可以理解，为减少最大长度将禁用此功能，因为这可能会导致数据丢失，但是，应该可以增加任何字段的最大长度。Drupal 7文本模块代码中的待办事项表明这是有意的，但从未实现。
需要发生的三件事：
- 更改field_data_ {fieldname}表中value列的VARCHAR长度
- 更改field_revision_ {fieldname}表中value列的VARCHAR长度
- 更新字段的配置以反映新的最大长度设置以下功能完成所有这三个步骤，并采用2个简单的参数，包括字段名称和新的最大长度。
/**
* Helper function to change the max length of a text field.
*/
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 = $field_name . '_value';
// Alter value field length in fields table.
db_query("UPDATE `{$field_table}` SET `{$field_column}`=SUBSTR(`{$field_column}`, 0, {$new_length})");
db_query("ALTER TABLE `{$field_table}` CHANGE `{$field_column}` `{$field_column}` VARCHAR( {$new_length} )");
// Alter value field length in fields revision table.
db_query("UPDATE `{$field_revision_table}` SET `{$field_column}`=SUBSTR(`{$field_column}`, 0, {$new_length})");
db_query("ALTER TABLE `{$field_revision_table}` CHANGE `{$field_column}` `{$field_column}` VARCHAR( {$new_length} )");
// Update field config with new max length.
$result = db_query("SELECT CAST(`data` AS CHAR(10000) CHARACTER SET utf8) FROM `field_config` WHERE field_name = '{$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();
}
自定义安装文件中提供此功能后，您可以创建一个新的数据库更新功能，该功能使用此新功能进行所需的更改。
/**
* Change max_length of Name field
*/
function mymodule_update_7002() {
MYMODULE_change_text_field_max_length('field_name', 50);
}
资料来源：http :
//nathan.rambeck.org/blog/42-modify-drupal-7-text-field-maximum-length
Drupal 8
这是@Christopher提出的相同功能的版本：
/**
* Utility to change the max length of a text field.
*
* @param string $field_name
* Field name.
* @param int $new_length
* Field length in characters.
*
* @throws \DrupalUpdateException
*/
function MYMODULE_change_text_field_max_length($field_name, $new_length) {
// The transaction opens here.
$txn = db_transaction();
try {
// Update field content tables with new max length.
foreach (['field_data_', 'field_revision_'] as $prefix) {
db_query('
ALTER TABLE {' . $prefix . $field_name . '}
MODIFY ' . $field_name . '_value VARCHAR( ' . $new_length . ' )
');
}
// Update field config record with new max length.
$result = db_query("
SELECT CAST(data AS CHAR(10000) CHARACTER SET utf8)
FROM {field_config}
WHERE field_name = :field_name
", [':field_name' => $field_name]
);
$config = $result->fetchField();
if ($config) {
$config_array = unserialize($config);
$config_array['settings']['max_length'] = $new_length;
$new_config = serialize($config_array);
db_update('field_config')
->fields(['data' => $new_config])
->condition('field_name', $field_name)
->execute();
}
}
catch (Exception $e) {
// Something went wrong somewhere, so roll back now.
$txn->rollback();
// Allow update to be re-run when errors are fixed.
throw new \DrupalUpdateException(
"Failed to change $field_name field max length: " . $e->getMessage(),
$e->getCode(), $e
);
}
}