The HTTP QUERY Method

Internet-Draft	The HTTP QUERY Method	February 2025
Reschke, et al.	Expires 27 August 2025	[Page]

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1. Introduction

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, this is a common query pattern:¶

GET /feed?q=foo&limit=10&sort=-published HTTP/1.1
Host: example.org

However, for a query with parameters that are complex or large, encoding it in the request URI may not be the best option because¶

often size limits are not known ahead of time because a request can pass through many uncoordinated system (but note that Section 4.1 of [HTTP] recommends senders and recipients to support at least 8000 octets),¶
expressing certain kinds of data in the target URI is inefficient because of the overhead of encoding that data into a valid URI, and¶
encoding query parameters directly into the request URI effectively casts every possible combination of query inputs as distinct resources.¶

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.¶

Summarizing:¶

Table 1
	GET	QUERY	POST
Safe	yes	yes	potentially no
Idempotent	yes	yes	potentially no
Cacheable	yes	yes	no
Content (body)	"no defined semantics"	expected (semantics per target resource)	expected (semantics per target resource)

1.1. Terminology

This document uses terminology defined in Section 3 of [HTTP].¶

1.2. Notational Conventions

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 [RFC2119] [RFC8174] when, and only when, they appear in all capitals, as shown here.¶

2. QUERY

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 Section 7.1 of [HTTP]), 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.¶

2.1. Content-Location and Location Fields

Furthermore, a successful response can include a Content-Location header field (see Section 8.7 of [HTTP]) 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 Section 10.2.2 of [HTTP]). 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.¶

2.2. Redirection

In some cases, the server may choose to respond indirectly to the QUERY request by redirecting the user agent to a different URI (see Section 15.4 of [HTTP]). 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 Appendix A.¶

2.3. Conditional Requests

A conditional QUERY requests that the selected representation (i.e., the query results, after any content negotiation) be returned in the response only under the circumstances described by the conditional header field(s), as defined in Section 13 of [HTTP].¶

2.4. Caching

The response to a QUERY method is cacheable; a cache MAY use it to satisfy subsequent QUERY requests as per Section 4 of [HTTP-CACHING]).¶

The cache key for a query (see Section 2 of [HTTP-CACHING]) 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 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.¶

2.5. Range Requests

The semantics of Range Requests for QUERY are identical to those for GET, as defined in Section 14 of [HTTP].¶

3. The "Accept-Query" Header Field

The "Accept-Query" response header field can 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" contains a list of media ranges (Section 12.5.1 of [HTTP]) using "Structured Fields" syntax ([STRUCTURED-FIELDS]). Media ranges are represented by a List Structured Header Field of either Tokens or Strings, containing the media range value without parameters. Parameters, if any, are mapped to Parameters of type String.¶

The choice of Token vs. String is semantically insignificant. That is, recipients MAY convert Tokens to Strings, but MUST NOT process them differently based on the received type.¶

Media types do not exactly map to Tokens, for instance they allow a leading digit. In cases like these, the String format needs to be used.¶

The only supported uses of wildcards are "*/*", which matches any type, or "xxxx/*", which matches any subtype of the indicated type.¶

The order of types listed in the field value is not significant.¶

The only allowed format for parameters is String.¶

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 value (per Section 4.2 of [HTTP-CACHING]) is used.¶

Example:¶

Accept-Query: "application/jsonpath", application/sql;charset="UTF-8"

Although the syntax for this field appears to be similar to other fields, such as "Accept" (Section 12.5.1 of [HTTP]), it is a Structured Field and thus MUST be processed as specified in Section 4 of [STRUCTURED-FIELDS].¶

5. IANA Considerations

5.1. Registration of QUERY method

IANA is requested to add the QUERY method to the HTTP Method Registry at <http://www.iana.org/assignments/http-methods> (see Section 16.3.1 of [HTTP]).¶

Table 2
Method Name	Safe	Idempotent	Specification
QUERY	Yes	Yes	Section 2

5.2. Registration of Accept-Query field

IANA is requested to add the Accept-Query field to the HTTP Field Name Registry at <https://www.iana.org/assignments/http-fields> (see Section 16.1.1 of [HTTP]).¶

Table 3
Field Name	Status	Structured Type	Reference	Comments
Accept-Query	permanent	List	Section 3 of this document.

Appendix A. Examples

The examples below are for illustrative purposes only; if one needs to send queries that are actually this short, it is probably better to use GET.¶

The media type used in most examples is "application/x-www-form-urlencoded" (as used in POST requests from browser user clients). The Content-Length fields have been omitted for brevity.¶

A.1. Simple Query

A simple query with a direct response:¶

QUERY /contacts HTTP/1.1
Host: example.org
Content-Type: application/x-www-form-urlencoded
Accept: application/json

select=surname,givenname,email&limit=10&match=%22email=*@example.*%22

Response:¶

HTTP/1.1 200 OK
Content-Type: application/json

[
  { "surname": "Smith",
    "givenname": "John",
    "email": "smith@example.org" },
  { "surname": "Jones",
    "givenname": "Sally",
    "email": "sally.jones@example.com" },
  { "surname": "Dubois",
    "givenname": "Camille",
    "email": "camille.dubois@example.net" }
]

A.2. Discovery of QUERY support

A simple way to discover support for QUERY is provided by the OPTIONS (Section 9.3.7 of [HTTP]) method:¶

OPTIONS /contacts HTTP/1.1
Host: example.org

Response:¶

HTTP/1.1 200 OK
Allow: GET, QUERY, OPTIONS, HEAD

The Allow response field (Section 10.2.1 of [HTTP]) denotes the set of supported methods on the specified resource.¶

There are alternatives to the use of OPTIONS. For instance, a QUERY request can be tried without prior knowledge of server support. The server would then either process the request, or could respond with a 4xx status such as 405 ("Method Not Allowed", Section 15.5.6 of [HTTP]), including the Allow response field.¶

A.3. Discovery of QUERY Formats

Discovery of supported media types for QUERY is possible via the Accept-Query (Section 3) response field:¶

HEAD /contacts HTTP/1.1
Host: example.org

Response:¶

HTTP/1.1 200 OK
Content-Type: application/xhtml
Accept-Query: application/x-www-form-urlencoded, application/sql

Responses to which request methods will contain Accept-Query will depend on the resource being accessed.¶

An alternative to checking Accept-Query would be to make a QUERY request, and then - in case of a 4xx status such as 415 ("Unsupported Media Type", Section 12.5.1 of [HTTP]) response - to inspect the Allow (Section 15.5.16 of [HTTP]) response field:¶

HTTP/1.1 415 Unsupported Media Type
Content-Type: application/xhtml
Accept: application/x-www-form-urlencoded, application/sql

A.4. Content-Location, Location, and Indirect Responses

The Content-Location and Location response fields provide a way to identify alternate resources that will respond to GET requests, either for the received result of the request, or for future requests to perform the same operation. Going back to the example from Appendix A.1:¶

QUERY /contacts HTTP/1.1
Host: example.org
Content-Type: application/x-www-form-urlencoded
Accept: application/json

select=surname,givenname,email&limit=10&match=%22email=*@example.*%22

Response:¶

HTTP/1.1 200 OK
Content-Type: application/json
Content-Location: /contacts/stored-results/17
Location: /contacts/stored-queries/42
Last-Modified: Sat, 25 Aug 2012 23:34:45 GMT
Date: Sun, 17 Nov 2024, 16:10:24 GMT

[
  { "surname": "Smith",
    "givenname": "John",
    "email": "smith@example.org" },
  { "surname": "Jones",
    "givenname": "Sally",
    "email": "sally.jones@example.com" },
  { "surname": "Dubois",
    "givenname": "Camille",
    "email": "camille.dubois@example.net" }
]

A.4.1. Using Content-Location

The Content-Location response field received above identifies a resource holding the result for the QUERY response it appeared on:¶

GET /contacts/stored-results/17 HTTP/1.1
Host: example.org
Accept: application/json

Response:¶

HTTP/1.1 200 OK
Last-Modified: Sat, 25 Aug 2012 23:34:45 GMT
Date: Sun, 17 Nov 2024, 16:10:25 GMT

[
  { "surname": "Smith",
    "givenname": "John",
    "email": "smith@example.org" },
  { "surname": "Jones",
    "givenname": "Sally",
    "email": "sally.jones@example.com" },
  { "surname": "Dubois",
    "givenname": "Camille",
    "email": "camille.dubois@example.net" }
]

A.4.2. Using Location

The Location response field identifies a resource that will respond to GET with a fresh result for the QUERY response it appeared on.¶

GET /contacts/stored-queries/42 HTTP/1.1
Host: example.org
Accept: application/json

In this example, one entry was removed at 2024-11-17T16:12:01Z (as indicated in the Last-Modified field), so the response only contains two entries:¶

HTTP/1.1 200 OK
Content-Type: application/json
Last-Modified: Sun, 17 November 2024, 16:12:01 GMT
ETag: "42-1"
Date: Sun, 17 Nov 2024, 16:13:17 GMT

[
  { "surname": "Smith",
    "givenname": "John",
    "email": "smith@example.org" },
  { "surname": "Dubois",
    "givenname": "Camille",
    "email": "camille.dubois@example.net" }
]

Assuming no change in the query result, a subsequent conditional GET request with¶

If-None-Match: "42-1"

would result in a 304 response ("Not Modified", Section 15.4.5 of [HTTP]).¶

Note that there's no guarantee that the server will implement this resource indefinitely, so, after an error response, the client would need to redo the original QUERY request in order to obtain a new alternative location.¶

A.4.3. Indirect Responses

Servers can send "indirect" responses using the status code 303 ("See Other", Section 15.4.4 of [HTTP]).¶

Given the request at the beginning of Appendix A.4, a server might respond with:¶

HTTP/1.1 303 See Other
Content-Type: text/plain
Date: Sun, 17 Nov 2024, 16:13:17 GMT
Location: /contacts/stored-queries/42

See stored query at "/contacts/stored-queries/42".

This is similar to including Location on a direct response, except that no result for the query is returned. This allows the server to only generate an alternative resource. This resource could then be used as shown in Appendix A.4.2.¶

A.5. More Query Formats

The following examples show requests on a JSON-shaped database of RFC errata.¶

The request below uses XSLT ([XSLT]) to extract errata information summarized per year and the defined errata types.¶

QUERY /errata.json HTTP/1.1
Host: example.org
Content-Type: application/xslt+xml
Accept: application/xml, text/csv

<transform xmlns="http://www.w3.org/1999/XSL/Transform"
  xmlns:j="http://www.w3.org/2005/xpath-functions"
  version="3.0">

  <output method="text"/>

  <param name="input"/>

  <variable name="json"
    select="json-to-xml(unparsed-text($input))"/>

  <variable name="sc">errata_status_code</variable>
  <variable name="sd">submit_date</variable>

  <template match="/">
    <text>year, total, rejected, verified, hdu, reported</text>
    <text>&#10;</text>
    <variable name="en" select="$json//j:map"/>
    <for-each-group select="$en"
      group-by="substring-before(j:string[@key=$sd],'-')">
      <sort select="current-grouping-key()"/>
      <variable name="year" select="current-grouping-key()"/>
      <variable name="errata" select=
        "$en[$year=substring-before(j:string[@key=$sd],'-')]"/>
      <value-of select="concat(
        $year,
        ', ',
        count($errata),
        ', ',
        count($errata['Rejected'=j:string[@key=$sc]]),
        ', ',
        count($errata['Verified'=j:string[@key=$sc]]),
        ', ',
        count(
          $errata['Held for Document Update'=j:string[@key=$sc]]),
        ', ',
        count($errata['Reported'=j:string[@key=$sc]]),
        '&#10;')"/>
    </for-each-group>
  </template>

</transform>

Response:¶

HTTP/1.1 200 OK
Content-Type: text/csv
Accept-Query: "application/jsonpath", "application/xslt+xml"
Date: Wed, 19 Feb 2025, 17:10:01 GMT

year, total, rejected, verified, hdu, reported
2000, 14, 0, 14, 0, 0
2001, 72, 1, 70, 1, 0
2002, 124, 8, 104, 12, 0
2003, 63, 0, 61, 2, 0
2004, 89, 1, 83, 5, 0
2005, 156, 10, 96, 50, 0
2006, 444, 54, 176, 214, 0
2007, 429, 48, 188, 193, 0
2008, 423, 52, 165, 206, 0
2009, 331, 39, 148, 144, 0
2010, 538, 80, 232, 222, 4
2011, 367, 47, 170, 150, 0
2012, 348, 54, 149, 145, 0
2013, 341, 61, 169, 106, 5
2014, 342, 73, 180, 72, 17
2015, 343, 79, 145, 89, 30
2016, 295, 46, 122, 82, 45
2017, 303, 46, 120, 84, 53
2018, 350, 61, 118, 98, 73
2019, 335, 47, 131, 94, 63
2020, 387, 68, 117, 123, 79
2021, 321, 44, 148, 63, 66
2022, 358, 37, 198, 40, 83
2023, 262, 38, 121, 33, 70
2024, 322, 33, 125, 23, 141
9999, 1, 0, 0, 1, 0

Note the Accept-Query response field indicating that another query format - JSONPath ([RFC9535]) - is supported as well. The request below would report the identifiers of all rejected errata submitted since 2024:¶

QUERY /errata.json HTTP/1.1
Host: example.org
Content-Type: application/jsonpath
Accept: application/json

$..[
     ?@.errata_status_code=="Rejected"
     && @.submit_date>"2024"
   ]
   ["doc-id"]

Response:¶

HTTP/1.1 200 OK
Content-Type: application/json
Accept-Query: "application/jsonpath", "application/xslt+xml"
Date: Thu, 20 Feb 2025, 09:55:42 GMT
Last-Modified: Thu, 20 Feb 2025 06:10:01 GMT

[
  "RFC1185","RFC8407","RFC6350","RFC8467","RFC1157","RFC9543",
  "RFC9076","RFC7656","RFC2822","RFC9460","RFC2104","RFC6797",
  "RFC9499","RFC9557","RFC2131","RFC2328","RFC9001","RFC3325",
  "RFC9438","RFC2526","RFC2985","RFC7643","RFC9132","RFC6376",
  "RFC9110","RFC9460","RFC7748","RFC9497","RFC8463","RFC4035",
  "RFC7239","RFC9083","RFC9537","RFC9537","RFC9420","RFC9000",
  "RFC9656","RFC9110","RFC2324","RFC2549","RFC6797","RFC2549",
  "RFC8894"
]