| `field` | yes | - | The field to insert, upsert, or update. Supports <<accessing-template-fields,template snippets>>.
| `value` | yes | - | The value to be set for the field. Supports <<accessing-template-fields,template snippets>>.
| `override` | no | true | If processor will update fields with pre-existing non-null-valued field. When set to `false`, such fields will not be touched.
| `ignore_empty_value` | no | `false` | If `true` and `value` is a <<accessing-template-fields,template snippet>> that evaluates to `null` or the empty string, the processor quietly exits without modifying the document