[[api-conventions]]
= API Conventions

[partintro]
--
The *elasticsearch* REST APIs are exposed using:

* <<modules-http,JSON over HTTP>>,
* <<modules-thrift,thrift>>,
* <<modules-memcached,memcached>>.

The conventions listed in this chapter can be applied throughout the REST
API, unless otherwise specified.

* <<multi-index>>
* <<common-options>>

--

[[multi-index]]
== Multiple Indices

Most APIs that refer to an `index` parameter support execution across multiple indices,
using simple `test1,test2,test3` notation (or `_all` for all indices). It also
support wildcards, for example: `test*`, and the ability to "add" (`+`)
and "remove" (`-`), for example: `+test*,-test3`.

All multi indices API support the `ignore_indices` option. Setting it to
`missing` will cause indices that do not exists to be ignored from the
execution. By default, when it's not set, the request will fail.

NOTE: Single index APIs such as the <<docs>> and the
<<indices-aliases,single-index `alias` APIs>> do not support multiple indices.

[[common-options]]
== Common options

The following options can be applied to all of the REST APIs.

[float]
=== Pretty Results

When appending `?pretty=true` to any request made, the JSON returned
will be pretty formatted (use it for debugging only!). Another option is
to set `format=yaml` which will cause the result to be returned in the
(sometimes) more readable yaml format.


[float]
=== Human readable output

Statistics are returned in a format suitable for humans
(eg `"exists_time": "1h"` or `"size": "1kb"`) and for computers
(eg `"exists_time_in_millis": 3600000`` or `"size_in_bytes": 1024`).
The human readable values can be turned off by adding `?human=false`
to the query string. This makes sense when the stats results are
being consumed by a monitoring tool, rather than intended for human
consumption.  The default for the `human` flag is
`false`. added[1.00.Beta,Previously defaulted to `true`]

[float]
=== Parameters

Rest parameters (when using HTTP, map to HTTP URL parameters) follow the
convention of using underscore casing.

[float]
=== Boolean Values

All REST APIs parameters (both request parameters and JSON body) support
providing boolean "false" as the values: `false`, `0`, `no` and `off`.
All other values are considered "true". Note, this is not related to
fields within a document indexed treated as boolean fields.

[float]
=== Number Values

All REST APIs support providing numbered parameters as `string` on top
of supporting the native JSON number types.

[[distance-units]]
[float]
=== Distance Units

Wherever distances need to be specified, such as the `distance` parameter in
the <<query-dsl-geo-distance-filter>>) or the `precision` parameter in the
<<query-dsl-geohash-cell-filter>>, the default unit if none is specified is
the meter. Distances can be specified in other units, such as `"1km"` or
`"2mi"` (2 miles).

The full list of units is listed below:

[horizontal]
Mile::          `mi` or `miles`
Yard::          `yd` or `yards`
Inch::          `in` or `inch`
Kilometer::     `km` or `kilometers`
Meter::         `m` or `meters`
Centimeter::    `cm` or `centimeters`
Millimeter::    `mm` or `millimeters`


[float]
=== Result Casing

All REST APIs accept the `case` parameter. When set to `camelCase`, all
field names in the result will be returned in camel casing, otherwise,
underscore casing will be used. Note, this does not apply to the source
document indexed.

[float]
=== JSONP

All REST APIs accept a `callback` parameter resulting in a
http://en.wikipedia.org/wiki/JSONP[JSONP] result.

[float]
=== Request body in query string

For libraries that don't accept a request body for non-POST requests,
you can pass the request body as the `source` query string parameter
instead.

[[url-access-control]]
== URL-based access control

Many users use a proxy with URL-based access control to secure access to
Elasticsearch indices. For <<search-multi-search,multi-search>>,
<<docs-multi-get,multi-get>> and <<docs-bulk,bulk>> requests, the user has
the choice of specifying an index in the URL and on each individual request
within the request body. This can make URL-based access control challenging.

To prevent the user from overriding the index which has been specified in the
URL, add this setting to the `config.yml` file:

    rest.action.multi.allow_explicit_index: false

The default value is `true`, but when set to `false`, Elasticsearch will
reject requests that have an explicit index specified in the request body.