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

File

drupal-7.x/modules/field/field.api.php, line 233

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'),
      ),
    ),
  );
}