OpenSearch/docs/reference/migration/migrate_3_0.asciidoc

[[breaking-changes-3.0]]
== Breaking changes in 3.0

This section discusses the changes that you need to be aware of when migrating
your application to Elasticsearch 3.0.

=== Search changes

==== `search_type=count` removed

The `count` search type was deprecated since version 2.0.0 and is now removed.
In order to get the same benefits, you just need to set the value of the `size`
parameter to `0`.

For instance, the following request:
[source,sh]
---------------
GET /my_index/_search?search_type=count
{
  "aggs": {
    "my_terms": {
       "terms": {
         "field": "foo"
       }
     }
  }
}
---------------

can be replaced with:
[source,sh]
---------------
GET /my_index/_search
{
  "size": 0,
  "aggs": {
    "my_terms": {
       "terms": {
         "field": "foo"
       }
     }
  }
}
---------------

==== `search_type=scan` removed

The `scan` search type was deprecated since version 2.1.0 and is now removed.
All benefits from this search type can now be achieved by doing a scroll
request that sorts documents in `_doc` order, for instance:

[source,sh]
---------------
GET /my_index/_search?scroll=2m
{
  "sort": [
    "_doc"
  ]
}
---------------

Scroll requests sorted by `_doc` have been optimized to more efficiently resume
from where the previous request stopped, so this will have the same performance
characteristics as the former `scan` search type.

=== Parent/Child changes

The `children` aggregation, parent child inner hits and `has_child` and `has_parent` queries will not work on indices
with `_parent` field mapping created before version `2.0.0`. The data of these indices need to be re-indexed into a new index.

The format of the join between parent and child documents have changed with the `2.0.0` release. The old
format can't read from version `3.0.0` and onwards. The new format allows for a much more efficient and
scalable join between parent and child documents and the join data structures are stored on on disk
data structures as opposed as before the join data structures were stored in the jvm heap space.

==== `score_type` has been removed

The `score_type` option has been removed from the `has_child` and `has_parent` queries in favour of the `score_mode` option
which does the exact same thing.

==== `sum` score mode removed

The `sum` score mode has been removed in favour of the `total` mode which doesn the same and is already available in
previous versions.

==== `max_children` option

When `max_children` was set to `0` on the `has_child` query then there was no upper limit on how many children documents
are allowed to match. This has changed and `0` now really means to zero child documents are allowed. If no upper limit
is needed then the `max_children` option shouldn't be defined at all on the `has_child` query.

=== Settings changes ===

==== Ping timeout settings

Previously, there were three settings for the ping timeout: `discovery.zen.initial_ping_timeout`,
`discovery.zen.ping.timeout` and `discovery.zen.ping_timeout`. The former two have been removed and
the only setting key for the ping timeout is now `discovery.zen.ping_timeout`. The default value for
ping timeouts remains at three seconds.

=== Plugins

Plugins implementing custom queries need to implement the `fromXContent(QueryParseContext)` method in their
`QueryParser` subclass rather than `parse`. This method will take care of parsing the query from `XContent` format
into an intermediate query representation that can be streamed between the nodes in binary format, effectively the
query object used in the java api. Also, the query parser needs to implement the `getBuilderPrototype` method that
returns a prototype of the `NamedWriteable` query, which allows to deserialize an incoming query by calling
`readFrom(StreamInput)` against it, which will create a new object, see usages of `Writeable`. The `QueryParser`
also needs to declare the generic type of the query that it supports and it's able to parse.
The query object can then transform itself into a lucene query through the new `toQuery(QueryShardContext)` method,
which returns a lucene query to be executed on the data node.

Similarly, plugins implementing custom score functions need to implement the `fromXContent(QueryParseContext)`
method in their `ScoreFunctionParser` subclass rather than `parse`. This method will take care of parsing
the function from `XContent` format into an intermediate function representation that can be streamed between
the nodes in binary format, effectively the function object used in the java api. Also, the query parser needs
to implement the `getBuilderPrototype` method that returns a prototype of the `NamedWriteable` function, which
allows to deserialize an incoming function by calling `readFrom(StreamInput)` against it, which will create a
new object, see usages of `Writeable`. The `ScoreFunctionParser` also needs to declare the generic type of the
function that it supports and it's able to parse. The function object can then transform itself into a lucene
function through the new `toFunction(QueryShardContext)` method, which returns a lucene function to be executed
on the data node.

=== Java-API

==== BoostingQueryBuilder

Removed setters for mandatory positive/negative query. Both arguments now have
to be supplied at construction time already and have to be non-null.

==== SpanContainingQueryBuilder

Removed setters for mandatory big/little inner span queries. Both arguments now have
to be supplied at construction time already and have to be non-null. Updated
static factory methods in QueryBuilders accordingly.

==== SpanOrQueryBuilder

Making sure that query contains at least one clause by making initial clause mandatory
in constructor.

==== SpanNearQueryBuilder

Removed setter for mandatory slop parameter, needs to be set in constructor now. Also
making sure that query contains at least one clause by making initial clause mandatory
in constructor. Updated the static factory methods in QueryBuilders accordingly.

==== SpanNotQueryBuilder

Removed setter for mandatory include/exclude span query clause, needs to be set in constructor now.
Updated the static factory methods in QueryBuilders and tests accordingly.

==== SpanWithinQueryBuilder

Removed setters for mandatory big/little inner span queries. Both arguments now have
to be supplied at construction time already and have to be non-null. Updated
static factory methods in QueryBuilders accordingly.

==== QueryFilterBuilder

Removed the setter `queryName(String queryName)` since this field is not supported
in this type of query. Use `FQueryFilterBuilder.queryName(String queryName)` instead
when in need to wrap a named query as a filter.

==== WrapperQueryBuilder

Removed `wrapperQueryBuilder(byte[] source, int offset, int length)`. Instead simply
use  `wrapperQueryBuilder(byte[] source)`. Updated the static factory methods in
QueryBuilders accordingly.

==== QueryStringQueryBuilder

Removed ability to pass in boost value using `field(String field)` method in form e.g. `field^2`.
Use the `field(String, float)` method instead.

==== Operator

Removed the enums called `Operator` from `MatchQueryBuilder`, `QueryStringQueryBuilder`,
`SimpleQueryStringBuilder`, and `CommonTermsQueryBuilder` in favour of using the enum
defined in `org.elasticsearch.index.query.Operator` in an effort to consolidate the
codebase and avoid duplication.

==== queryName and boost support

Support for `queryName` and `boost` has been streamlined to all of the queries. That is
a breaking change till queries get sent over the network as serialized json rather
than in `Streamable` format. In fact whenever additional fields are added to the json
representation of the query, older nodes might throw error when they find unknown fields.

==== InnerHitsBuilder

InnerHitsBuilder now has a dedicated addParentChildInnerHits and addNestedInnerHits methods
to differentiate between inner hits for nested vs. parent / child documents. This change
makes the type / path parameter mandatory.

==== MatchQueryBuilder

Moving MatchQueryBuilder.Type and MatchQueryBuilder.ZeroTermsQuery enum to MatchQuery.Type.
Also reusing new Operator enum.

==== MoreLikeThisQueryBuilder

Removed `MoreLikeThisQueryBuilder.Item#id(String id)`, `Item#doc(BytesReference doc)`,
`Item#doc(XContentBuilder doc)`. Use provided constructors instead.

Removed `MoreLikeThisQueryBuilder#addLike` in favor of texts and/or items beeing provided
at construction time. Using arrays there instead of lists now.

Removed `MoreLikeThisQueryBuilder#addUnlike` in favor to using the `unlike` methods
which take arrays as arguments now rather than the lists used before.

The deprecated `docs(Item... docs)`, `ignoreLike(Item... docs)`,
`ignoreLike(String... likeText)`, `addItem(Item... likeItems)` have been removed.

==== GeoDistanceQueryBuilder

Removing individual setters for lon() and lat() values, both values should be set together
 using point(lon, lat).

==== GeoDistanceRangeQueryBuilder

Removing setters for to(Object ...) and from(Object ...) in favour of the only two allowed input
arguments (String, Number). Removing setter for center point (point(), geohash()) because parameter
is mandatory and should already be set in constructor.
Also removing setters for lt(), lte(), gt(), gte() since they can all be replaced by equivallent
calls to to/from() and inludeLower()/includeUpper().

==== GeoPolygonQueryBuilder

Require shell of polygon already to be specified in constructor instead of adding it pointwise.
This enables validation, but makes it necessary to remove the addPoint() methods.

==== MultiMatchQueryBuilder

Moving MultiMatchQueryBuilder.ZeroTermsQuery enum to MatchQuery.ZeroTermsQuery.
Also reusing new Operator enum.

Removed ability to pass in boost value using `field(String field)` method in form e.g. `field^2`.
Use the `field(String, float)` method instead.

==== MissingQueryBuilder

The two individual setters for existence() and nullValue() were removed in favour of
optional constructor settings in order to better capture and validate their interdependent
settings at construction time.

==== TermsQueryBuilder

Remove the setter for `termsLookup()`, making it only possible to either use a TermsLookup object or
individual values at construction time. Also moving individual settings for the TermsLookup (lookupIndex,
lookupType, lookupId, lookupPath) to the separate TermsLookup class, using constructor only and moving
checks for validation there. Removed `TermsLookupQueryBuilder` in favour of `TermsQueryBuilder`.

==== FunctionScoreQueryBuilder

`add` methods have been removed, all filters and functions must be provided as constructor arguments by
creating an array of `FunctionScoreQueryBuilder.FilterFunctionBuilder` objects, containing one element
for each filter/function pair.

`scoreMode` and `boostMode` can only be provided using corresponding enum members instead
of string values: see `FilterFunctionScoreQuery.ScoreMode` and `CombineFunction`.

`CombineFunction.MULT` has been renamed to `MULTIPLY`.