[[breaking-changes-2.0]]
== Breaking changes in 2.0

This section discusses the changes that you need to be aware of when migrating
your application to Elasticsearch 2.0.

=== Indices API

The <<alias-retrieving, get alias api>> will, by default produce an error response 
if a requested index does not exist. This change brings the defaults for this API in 
line with the other Indices APIs. The <<multi-index>> options can be used on a request 
to change this behavior

`GetIndexRequest.features()` now returns an array of Feature Enums instrad of an array of String values.
The following deprecated methods have been removed:
* `GetIndexRequest.addFeatures(String[])` - Please use `GetIndexRequest.addFeatures(Feature[])` instead
* `GetIndexRequest.features(String[])` - Please use `GetIndexRequest.features(Feature[])` instead
* `GetIndexRequestBuilder.addFeatures(String[])` - Please use `GetIndexRequestBuilder.addFeatures(Feature[])` instead
* `GetIndexRequestBuilder.setFeatures(String[])` - Please use `GetIndexRequestBuilder.setFeatures(Feature[])` instead

=== Partial fields

Partial fields were deprecated since 1.0.0beta1 in favor of <<search-request-source-filtering,source filtering>>.

=== More Like This Field

The More Like This Field query has been removed in favor of the <<query-dsl-mlt-query, More Like This Query>>
restrained set to a specific `field`.

=== Routing

The default hash function that is used for routing has been changed from djb2 to
murmur3. This change should be transparent unless you relied on very specific
properties of djb2. This will help ensure a better balance of the document counts
between shards.

In addition, the following node settings related to routing have been deprecated:

[horizontal]

`cluster.routing.operation.hash.type`::

  This was an undocumented setting that allowed to configure which hash function
  to use for routing. `murmur3` is now enforced on new indices.

`cluster.routing.operation.use_type`::

  This was an undocumented setting that allowed to take the `_type` of the
  document into account when computing its shard (default: `false`). `false` is
  now enforced on new indices.