public static interface NormalizationOperation.Operation
**copy** - Copies the value of the **source_field** to the **destination_field** field. If the **destination_field** already exists, then the value of the **source_field** overwrites the original value of the **destination_field**.
**move** - Renames (moves) the **source_field** to the **destination_field**. If the **destination_field** already exists, then the value of the **source_field** overwrites the original value of the **destination_field**. Rename is identical to copy, except that the **source_field** is removed after the value has been copied to the **destination_field** (it is the same as a _copy_ followed by a _remove_).
**merge** - Merges the value of the **source_field** with the value of the **destination_field**. The **destination_field** is converted into an array if it is not already an array, and the value of the **source_field** is appended to the array. This operation removes the **source_field** after the merge. If the **source_field** does not exist in the current document, then the **destination_field** is still converted into an array (if it is not an array already). This conversion ensures the type for **destination_field** is consistent across all documents.
**remove** - Deletes the **source_field** field. The **destination_field** is ignored for this operation.
**remove_nulls** - Removes all nested null (blank) field values from the ingested document. **source_field** and **destination_field** are ignored by this operation because _remove_nulls_ operates on the entire ingested document. Typically, **remove_nulls** is invoked as the last normalization operation (if it is invoked at all, it can be time-expensive).
| Modifier and Type | Field and Description | 
|---|---|
static java.lang.String | 
COPY
copy. 
 | 
static java.lang.String | 
MERGE
merge. 
 | 
static java.lang.String | 
MOVE
move. 
 | 
static java.lang.String | 
REMOVE
remove. 
 | 
static java.lang.String | 
REMOVE_NULLS
remove_nulls. 
 | 
static final java.lang.String COPY
static final java.lang.String MOVE
static final java.lang.String MERGE
static final java.lang.String REMOVE
static final java.lang.String REMOVE_NULLS