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The HTTP QUERY Method
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malhotrasahib@gmail.com
jasnell@gmail.com
Akamai
mbishop@evequefou.be
Web and Internet Transport
HTTP
http
query
method
This specification defines a new HTTP method, QUERY, as a safe, idempotent
request method that can carry request content.
Discussion of this draft takes place on the HTTP working group
mailing list (ietf-http-wg@w3.org), which is archived at
.
Working Group information can be found at ;
source code and issues list for this draft can be found at
.
The changes in this draft are summarized in .
This specification defines the HTTP QUERY request method as a means of
making a safe, idempotent request that contains content.
Most often, this is desirable when the data conveyed in a request is
too voluminous to be encoded into the request’s URI. For example, while
this is an common and interoperable query:
GET /feed?q=foo&limit=10&sort=-published HTTP/1.1
Host: example.org
if the query parameters extend to several kilobytes or more of
data it may not be, because many implementations place limits on their size. Often these limits are not
known or discoverable ahead of time, because a request can pass through many uncoordinated
systems. Additionally, expressing certain kinds of data in the target URI is inefficient, because it
needs to be encoded to be a valid URI.
Encoding query parameters directly into the request URI also effectively
casts every possible combination of query inputs as distinct
resources. Depending on the application, that may not be desirable.
As an alternative to using GET, many implementations make use of the
HTTP POST method to perform queries, as illustrated in the example
below. In this case, the input parameters to the query operation are
passed along within the request content as opposed to using the
request URI.
A typical use of HTTP POST for requesting a query:
POST /feed HTTP/1.1
Host: example.org
Content-Type: application/x-www-form-urlencoded
q=foo&limit=10&sort=-published
This variation, however, suffers from the same basic limitation as GET
in that it is not readily apparent — absent specific knowledge of the
resource and server to which the request is being sent — that a safe,
idempotent query is being performed.
The QUERY method provides a solution that spans the gap between the use of GET and POST, with
the example above being expressed as:
QUERY /feed HTTP/1.1
Host: example.org
Content-Type: application/x-www-form-urlencoded
q=foo&limit=10&sort=-published
As with POST, the input to the query operation is passed along within the content of the request
rather than as part of the request URI. Unlike POST, however, the method is explicitly safe
and idempotent, allowing functions like caching and automatic retries to operate.
The key words “MUST”, “MUST NOT”, “REQUIRED”, “SHALL”, “SHALL
NOT”, “SHOULD”, “SHOULD NOT”, “RECOMMENDED”, “NOT RECOMMENDED”,
“MAY”, and “OPTIONAL” in this document are to be interpreted as
described in BCP 14 when, and only when, they
appear in all capitals, as shown here.
The QUERY method is used to initiate a server-side query. Unlike
the HTTP GET method, which requests that a server return a
representation of the resource identified by the target URI
(as defined by ), the QUERY
method is used to ask the server to perform a query operation
(described by the request content) over some set of data scoped to the
target URI. The content returned in response to a QUERY
cannot be assumed to be a representation of the resource identified by
the target URI.
The content of the request defines the query. Implementations &MAY; use
a request content of any media type with the QUERY method, provided that it
has appropriate query semantics.
QUERY requests are both safe and idempotent with regards to the
resource identified by the request URI. That is, QUERY requests do not
alter the state of the targeted resource. However, while processing a
QUERY request, a server can be expected to allocate computing and memory
resources or even create additional HTTP resources through which the
response can be retrieved.
A successful response to a QUERY request is expected to provide some
indication as to the final disposition of the operation. For
instance, a successful query that yields no results can be represented
by a 204 No Content response. If the response includes content,
it is expected to describe the results of the operation.
Furthermore, a successful response can include a Content-Location
header field (see ) containing an
identifier for a resource corresponding to the results of the
operation. This represents a claim from the server that a client can send
a GET request for the indicated URI to retrieve the results of the query
operation just performed. The indicated resource might be temporary.
A server &MAY; create or locate a resource that identifies the query
operation for future use. If the server does so, the URI of the resource
can be included in the Location header field of the response (see ). This represents a claim that a client can
send a GET request to the indicated URI to repeat the query operation just
performed without resending the query parameters. This resource might be
temporary; if a future request fails, the client can retry using the
original QUERY resource and the previously submitted parameters again.
In some cases, the server may choose to respond indirectly to the QUERY
request by redirecting the user agent to a different URI (see
). The semantics of the redirect
response do not differ from other methods. For instance, a 303 (See Other)
response would indicate that the Location field identifies an
alternate URI from which the results can be retrieved
using a GET request (this use case is also covered by the
use of the Location response field in a 2xx response).
On the other hand, response codes 307 (Temporary Redirect) and 308
(Permanent Redirect) can be used to request the user agent to redo
the QUERY request on the URI specified by the Location field.
Various non-normative examples of successful
QUERY responses are illustrated in .
The semantics of the QUERY method change to a “conditional QUERY” if
the request message includes an If-Modified-Since, If-Unmodified-
Since, If-Match, If-None-Match, or If-Range header field
(). A conditional QUERY requests that the query
be performed only under the circumstances described by the conditional
header field(s). It is important to note, however, that such conditions
are evaluated against the state of the target resource itself as opposed
to the collected results of the query operation.
The response to a QUERY method is cacheable; a cache &MAY; use it to satisfy subsequent
QUERY requests as per ).
The cache key for a query (see ) &MUST;
incorporate the request content. When doing so, caches &SHOULD; first normalize request
content to remove semantically insignificant differences, thereby improving cache
efficiency, by:
- Removing content encoding(s)
- Normalizing based upon knowledge of format conventions, as indicated by the any media type suffix in the request’s Content-Type field (e.g., “+json”)
- Normalizing based upon knowledge of the semantics of the content itself, as indicated by the request’s Content-Type field.
Note that any such normalization is performed solely for the purpose of generating a cache key; it
does not change the request itself.
The “Accept-Query” response header field &MAY; be used by a resource to
directly signal support for the QUERY method while identifying
the specific query format media type(s) that may be used.
Accept-Query = 1#media-type
The Accept-Query header field specifies a comma-separated listing of media
types (with optional parameters) as defined by
. field syntax currently discussed in
The order of types listed by the Accept-Query header field is not significant.
Accept-Query’s value applies to every URI on the server that shares the same path; in
other words, the query component is ignored. If requests to the same resource return
different Accept-Query values, the most recently received fresh (per
) value is used.
The non-normative examples in this section make use of a simple,
hypothetical plain-text based query syntax based on SQL with results
returned as comma-separated values. This is done for illustration
purposes only. Implementations are free to use any format they wish on
both the request and response.
A simple query with a direct response:
QUERY /contacts HTTP/1.1
Host: example.org
Content-Type: example/query
Accept: text/csv
select surname, givenname, email limit 10
Response:
HTTP/1.1 200 OK
Content-Type: text/csv
surname, givenname, email
Smith, John, john.smith@example.org
Jones, Sally, sally.jones@example.com
Dubois, Camille, camille.dubois@example.net
A simple query with a direct response:
QUERY /contacts HTTP/1.1
Host: example.org
Content-Type: example/query
Accept: text/csv
select surname, givenname, email limit 10
Response:
HTTP/1.1 200 OK
Content-Type: text/csv
Content-Location: /contacts/responses/42
Location: /contacts/queries/17
surname, givenname, email
Smith, John, john.smith@example.org
Jones, Sally, sally.jones@example.com
Dubois, Camille, camille.dubois@example.net
A subsequent GET request on /contacts/responses/42 would return
the same response, until the server decides to remove that
resource.
A GET request on /contacts/queries/17 however would execute the same
query again, and return a fresh result for that query:
GET /contacts/queries/17 HTTP/1.1
Host: example.org
Accept: text/csv
Response:
HTTP/1.1 200 OK
Content-Type: text/csv
Content-Location: /contacts/responses/43
surname, givenname, email
Jones, Sally, sally.jones@example.com
Dubois, Camille, camille.dubois@example.net
A simple query with an Indirect Response (303 See Other):
QUERY /contacts HTTP/1.1
Host: example.org
Content-Type: example/query
Accept: text/csv
select surname, givenname, email limit 10
Response:
HTTP/1.1 303 See Other
Location: /contacts/query123
Retrieval of the Query Response:
GET /contacts/query123 HTTP/1.1
Host: example.org
Response:
HTTP/1.1 200 OK
Content-Type: text/csv
surname, givenname, email
Smith, John, john.smith@example.org
Jones, Sally, sally.jones@example.com
Dubois, Camille, camille.dubois@example.net
A simple query being redirected:
QUERY /contacts HTTP/1.1
Host: example.org
Content-Type: example/query
Accept: text/csv
select surname, givenname, email limit 10
Response:
HTTP/1.1 308 Moved Permanently
Location: /morecontacts
Redirected request:
QUERY /morecontacts HTTP/1.1
Host: example.org
Content-Type: example/query
Accept: text/csv
select surname, givenname, email limit 10
Response:
HTTP/1.1 200 OK
Content-Type: text/csv
surname, givenname, email
Smith, John, john.smith@example.org
Jones, Sally, sally.jones@example.com
Dubois, Camille, camille.dubois@example.net
The QUERY method is subject to the same general security
considerations as all HTTP methods as described in
.
The QUERY method can be used as an alternative to passing query
information in the query portion of a URI. This is preferred in some
cases, as the URI is more likely to be logged than the request content. If
a server creates a temporary resource to represent the results of a QUERY
request (e.g., for use in the Location or Content-Location field) and the request
contains sensitive information that cannot be logged, then the URI of this
resource &SHOULD; be chosen such that it does not include any sensitive
portions of the original request content.
IANA is requested to add the QUERY method to the HTTP
Method Registry at
(see ).
| Method Name |
Safe |
Idempotent |
Specification |
| QUERY |
Yes |
Yes |
|
IANA is requested to add the Accept-Query field to the HTTP Field Name
Registry at
(see ).
| Field Name |
Status |
Structured Type |
Reference |
Comments |
| Accept-Query |
permanent |
|
of this document. |
field syntax currently discussed in |
HTTP Semantics
HTTP Caching
- Use “example/query” media type instead of undefined “text/query” ()
- In , adjust the grammar to just define the field value ()
- Update to latest HTTP core spec, and adjust terminology accordingly ()
- Reference RFC 8174 and markup bcp14 terms ()
- Update HTTP reference ()
- Relax restriction of generic XML media type in request content ()
- Add minimal description of cacheability ()
- Use “QUERY” as method name ()
- Update HTTP reference ()
- In , slightly rephrase statement about significance of ordering ()
- Throughout: use “content” instead of “payload” or “body” ()
- Updated references ()
- Describe role of Content-Location and Location fields ()
- Added Mike Bishop as author ()
- Use “target URI” instead of “effective request URI” ()
- Updated language and examples about redirects and method rewriting ()
- Add QUERY example to introduction ()
- Update “Sensitive information in QUERY URLs” ()
- Field registration for “Accept-Query” ()