Deleting Drupal Fields programmatically implementing hook_update_N()

Say we’d like to get rid of a Drupal Field that has the machine name field_wein_texte and our module that’s supposed to manage this is called kx_deployment. Here’s how the kx_deployment.install needs to look like:

<?php
/**
* Implements hook_update_N().
* Managing Field Deletions programmatically
* Note: field_delete_fields() removes fields globally, to detach a field from an entity use field_delete_instance()
*/
function kx_deployment_update_7001() {
  $fields_to_delete = array(
    'field_wein_texte',
  );
  foreach ($fields_to_delete as $field_name) {
    field_delete_field($field_name);
    watchdog('kx_deployment', 'Deleted the :field_name field from all content type instances.', array(':field_name' => $field_name));
  }
}
// The fields aren't really deleted until the purge function runs, ordinarily
// during cron.  Count the number of fields we need to purge, and add five in
// case a few other miscellaneous fields are in there somehow.
if(isset($fields_to_delete)) {
  field_purge_batch(count($fields_to_delete) + 5);
}
?>

Source: http://data.agaric.com/deleting-drupal-fields-programmatically-so-change-field-type-features