Nik Everett 4b1c116461 Generate and run tests from the docs
Adds infrastructure so `gradle :docs:check` will extract tests from
snippets in the documentation and execute the tests. This is included
in `gradle check` so it should happen on CI and during a normal build.

By default each `// AUTOSENSE` snippet creates a unique REST test. These
tests are executed in a random order and the cluster is wiped between
each one. If multiple snippets chain together into a test you can annotate
all snippets after the first with `// TEST[continued]` to have the
generated tests for both snippets joined.

Snippets marked as `// TESTRESPONSE` are checked against the response
of the last action.

See docs/README.asciidoc for lots more.

Closes #12583. That issue is about catching bugs in the docs during build.
This catches *some* bugs in the docs during build which is a good start.
2016-05-05 13:58:03 -04:00

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[[mapping-store]]
=== `store`
By default, field values are <<mapping-index,indexed>> to make them searchable,
but they are not _stored_. This means that the field can be queried, but the
original field value cannot be retrieved.
Usually this doesn't matter. The field value is already part of the
<<mapping-source-field,`_source` field>>, which is stored by default. If you
only want to retrieve the value of a single field or of a few fields, instead
of the whole `_source`, then this can be achieved with
<<search-request-source-filtering,source filtering>>.
In certain situations it can make sense to `store` a field. For instance, if
you have a document with a `title`, a `date`, and a very large `content`
field, you may want to retrieve just the `title` and the `date` without having
to extract those fields from a large `_source` field:
[source,js]
--------------------------------------------------
PUT my_index
{
"mappings": {
"my_type": {
"properties": {
"title": {
"type": "text",
"store": true <1>
},
"date": {
"type": "date",
"store": true <1>
},
"content": {
"type": "text"
}
}
}
}
}
PUT my_index/my_type/1
{
"title": "Some short title",
"date": "2015-01-01",
"content": "A very long content field..."
}
GET my_index/_search
{
"fields": [ "title", "date" ] <2>
}
--------------------------------------------------
// AUTOSENSE
<1> The `title` and `date` fields are stored.
<2> This request will retrieve the values of the `title` and `date` fields.
[NOTE]
.Stored fields returned as arrays
======================================
For consistency, stored fields are always returned as an _array_ because there
is no way of knowing if the original field value was a single value, multiple
values, or an empty array.
If you need the original value, you should retrieve it from the `_source`
field instead.
======================================
Another situation where it can make sense to make a field stored is for those
that don't appear in the `_source` field (such as <<copy-to,`copy_to` fields>>).