DocumentMutation.merge()

Operations Performed

Verifies that a field at the specified path exists. If the field at the specified path does not exist, this operation creates it with the specified value.
Verifies that the field is of the Map type.
Merges the passed value with the existing value.

Example of Merging Documents

Original document

{
    "_id" : "000001",
    "a" : {
        "b" : {
            "c" : 1,
            "d" : "abd",
            "e" : 2
           }
      }
}

Document to merge at the field path a.b

{
    "c" : 3,
    "d" : "replacedString",
    "newField1" : "newStringValue",
    "newField2" : 4
}

Example code for the merge

  public Document buildDocument() {
    return MapRDB.newDocument()
      .set("c", 3)
      .set("d", "replacedString")
      .set(newField1", "newStringValue")
      .set(newField2", 4);
  }


  public DocumentMutation buildDocumentMutation() {
    return MapRDB.newDocumentMutation()
      .merge("a", ImmutableMap.of(
        "b", document));
  }

  public void update(String tablePath, DocumentMutation mutation, String _id) {
    try(Table table = MapRDB.getTable(tablePath)) {
      table.update(_id, mutation);
    }
  }

Parameter	Description
`_id`	The value of the document's `_id` field.
`tablePath`	The path of the table in the MapR file system. See Table Paths.

Mergred document

{ 
   "_id" : "000001", 
   "a":{  
      "b":{  
         "e":2,
         "c":3,
         "d":"replacedString",
         "newField1":"newStrValue",
         "newField2":4
      }
   }
}

Permissions Required

The readAce and writeAce permissions on the volumes where the JSON tables that contain the documents are located. For information about how to set permissions on volumes, see Setting/Modifying Whole Volume ACEs.
readperm and writeperm on the specified field, if this field exists. See How to Obtain readperm and writeperm on a Field.
writeperm on the parent field, if the specified field does not exist. See How to Obtain readperm or writeperm on a Field.

Link to Javadoc

DocumentMutation

IMPORTANT: If a DocumentMutation object modifies a field two or more times, only the final operation on that field is applied.

Example One

table.update() in the last line fails with error code 22:

DBDocument doc = MapRDB.newDocument()
        .set("int", 100)
        .set("date", new Date(1000))
        .set("string", "a string");

table.insertOrReplace("doc1", doc);

// Set different fields
DocumentMutation mutation = MapRDB.newDocumentMutation();
mutation.setOrReplace("string", 1000);
mutation.set("string", 2000);

table.update("doc1", mutation);

Example Two

This code results in the document {"string":"a string add3"}, rather than the document {"string":"a string add1 add2 add3"}.

DBDocument doc = MapRDB.newDocument()
        .set("string", "a string");

table.insertOrReplace("doc1", record);

DocumentMutation mutation = MapRDB.newDocumentMutation();
mutation.append("string", " add1");
mutation.append("string", " add2");
mutation.append("string", " add3");

table.update("doc1", mutation);