function hook_field_schema

Define the Field API schema for a field structure.

This hook MUST be defined in .install for it to be detected during installation and upgrade.

Parameters

$field: A field structure.

Return value

An associative array with the following keys:

  • columns: An array of Schema API column specifications, keyed by column name. This specifies what comprises a value for a given field. For example, a value for a number field is simply 'value', while a value for a formatted text field is the combination of 'value' and 'format'. It is recommended to avoid having the column definitions depend on field settings when possible. No assumptions should be made on how storage engines internally use the original column name to structure their storage.
  • indexes: (optional) An array of Schema API index definitions. Only columns that appear in the 'columns' array are allowed. Those indexes will be used as default indexes. Callers of field_create_field() can specify additional indexes or, at their own risk, modify the default indexes specified by the field-type module. Some storage engines might not support indexes.
  • foreign keys: (optional) An array of Schema API foreign key definitions.

Related topics

9 functions implement hook_field_schema()

Note: this list is generated by pattern matching, so it may include some functions that are not actually implementations of this hook.

email_field_schema in drupal/core/modules/field/modules/email/email.install
Implements hook_field_schema().
field_test_field_schema in drupal/core/modules/field/tests/modules/field_test/field_test.install
Implements hook_field_schema().
file_field_schema in drupal/core/modules/file/file.install
Implements hook_field_schema().
image_field_schema in drupal/core/modules/image/image.install
Implements hook_field_schema().
link_field_schema in drupal/core/modules/field/modules/link/link.install
Implements hook_field_schema().

... See full list

4 invocations of hook_field_schema()
field_create_field in drupal/core/modules/field/field.crud.inc
Creates a field.
field_read_fields in drupal/core/modules/field/field.crud.inc
Reads in fields that match an array of conditions.
field_update_field in drupal/core/modules/field/field.crud.inc
Updates a field.
_update_7000_field_create_field in drupal/core/modules/field/field.install
Creates a field by writing directly to the database.

File

drupal/core/modules/field/field.api.php, line 224

Code

function hook_field_schema($field) {
  if ($field['type'] == 'text_long') {
    $columns = array(
      'value' => array(
        'type' => 'text',
        'size' => 'big',
        'not null' => FALSE,
      ),
    );
  }
  else {
    $columns = array(
      'value' => array(
        'type' => 'varchar',
        'length' => $field['settings']['max_length'],
        'not null' => FALSE,
      ),
    );
  }
  $columns += array(
    'format' => array(
      'type' => 'varchar',
      'length' => 255,
      'not null' => FALSE,
    ),
  );
  return array(
    'columns' => $columns,
    'indexes' => array(
      'format' => array(
        'format',
      ),
    ),
    'foreign keys' => array(
      'format' => array(
        'table' => 'filter_format',
        'columns' => array(
          'format' => 'format',
        ),
      ),
    ),
  );
}