OpenSearch/docs/reference/migration/migrate_2_0/search.asciidoc

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=== Search changes
==== Partial fields
Partial fields have been removed in favor of <<search-request-source-filtering,source filtering>>.
==== `search_type=count` deprecated
The `count` search type has been deprecated. All benefits from this search
type can now be achieved by using the (default) `query_then_fetch` search type
and setting `size` to `0`.
==== The count api internally uses the search api
The count api is now a shortcut to the search api with `size` set to 0. As a
result, a total failure will result in an exception being returned rather
than a normal response with `count` set to `0` and shard failures.
==== All stored meta-fields returned by default
Previously, meta-fields like `_routing`, `_timestamp`, etc would only be
included in the search results if specifically requested with the `fields`
parameter. Now, all meta-fields which have stored values will be returned by
default. Additionally, they are now returned at the top level (along with
`_index`, `_type`, and `_id`) instead of in the `fields` element.
For instance, the following request:
[source,sh]
---------------
GET /my_index/_search?fields=foo
---------------
might return:
[source,js]
---------------
{
[...]
"hits": {
"total": 1,
"max_score": 1,
"hits": [
{
"_index": "my_index",
"_type": "my_type",
"_id": "1",
"_score": 1,
"_timestamp": 10000000, <1>
"fields": {
"foo" : [ "bar" ]
}
}
]
}
}
---------------
<1> The `_timestamp` is returned by default, and at the top level.
==== Script fields
Script fields in 1.x were only returned as a single value. Even if the return
value of a script was a list, it would be returned as an array containing an
array:
[source,js]
---------------
"fields": {
"my_field": [
[
"v1",
"v2"
]
]
}
---------------
In elasticsearch 2.0, scripts that return a list of values are treated as
multivalued fields. The same example would return the following response, with
values in a single array.
[source,js]
---------------
"fields": {
"my_field": [
"v1",
"v2"
]
}
---------------
==== Timezone for date field
Specifying the `time_zone` parameter in queries or aggregations on fields of
type `date` must now be either an ISO 8601 UTC offset, or a timezone id. For
example, the value `+1:00` must now be written as `+01:00`.
==== Only highlight queried fields
The default value for the `require_field_match` option has changed from
`false` to `true`, meaning that the highlighters will, by default, only take
the fields that were queried into account.
This means that, when querying the `_all` field, trying to highlight on any
field other than `_all` will produce no highlighted snippets. Querying the
same fields that need to be highlighted is the cleaner solution to get
highlighted snippets back. Otherwise `require_field_match` option can be set
to `false` to ignore field names completely when highlighting.
The postings highlighter doesn't support the `require_field_match` option
anymore, it will only highlight fields that were queried.
==== Postings highlighter doesn't support `match_phrase_prefix`
The `match` query with type set to `phrase_prefix` (or the
`match_phrase_prefix` query) is not supported by the postings highlighter. No
highlighted snippets will be returned.