function hook_field_schema in Drupal 7

Define the Field API schema for a field structure.

This is invoked when a field is created, in order to obtain the database schema from the module that defines the field's type.

This hook must be defined in the module's .install file 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 indexes 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 keys definitions.

Related topics

7 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.

field_test_field_schema in modules/field/tests/field_test.install

Implements hook_field_schema().

file_field_schema in modules/file/file.install

Implements hook_field_schema().

image_field_schema in modules/image/image.install

Implements hook_field_schema().

list_field_schema in modules/field/modules/list/list.install

Implements hook_field_schema().

number_field_schema in modules/field/modules/number/number.install

Implements hook_field_schema().

... See full list

5 invocations of hook_field_schema()

field_create_field in modules/field/field.crud.inc

Creates a field.

field_read_fields in modules/field/field.crud.inc

Reads in fields that match an array of conditions.

field_update_7001 in modules/field/field.install

Fix fields definitions created during the d6 to d7 upgrade path.

field_update_field in modules/field/field.crud.inc

Updates a field.

_update_7000_field_create_field in modules/field/field.install

Utility function: create a field by writing directly to the database.

File

modules/field/field.api.php, line 241

Hooks provided by the Field module.

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',
        ),
      ),
    ),
  );
}