.. Licensed under the Apache License, Version 2.0 (the "License"); you may not
.. use this file except in compliance with the License. You may obtain a copy of
.. the License at
..
..   http://www.apache.org/licenses/LICENSE-2.0
..
.. Unless required by applicable law or agreed to in writing, software
.. distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
.. WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
.. License for the specific language governing permissions and limitations under
.. the License.

.. _api/ddoc/view:

==========================================
``/db/_design/design-doc/_view/view-name``
==========================================

.. http:get:: /{db}/_design/{ddoc}/_view/{view}
    :synopsis: Returns results for the specified stored view

    Executes the specified view function from the specified design document.

    :param db: Database name
    :param ddoc: Design document name
    :param view: View function name

    :<header Accept: - :mimetype:`application/json`
                     - :mimetype:`text/plain`

    :query boolean conflicts: Includes `conflicts` information in response.
      Ignored if `include_docs` isn't ``true``. Default is ``false``
    :query boolean descending: Return the documents in descending by key order.
      Default is ``false``
    :query json endkey: Stop returning records when the specified key is
      reached. *Optional*
    :query json end_key: Alias for `endkey` param
    :query string endkey_docid: Stop returning records when the specified
      document ID is reached. Requires ``endkey`` to be specified for this to
      have any effect. *Optional*
    :query string end_key_doc_id: Alias for `endkey_docid` param
    :query boolean group: Group the results using the reduce function to a
      group or single row. Default is ``false``
    :query number group_level: Specify the group level to be used. *Optional*
    :query boolean include_docs: Include the associated document with each row.
      Default is ``false``.
    :query boolean attachments: Include the Base64-encoded content of
      :ref:`attachments <api/doc/attachments>` in the documents that are
      included if `include_docs` is ``true``. Ignored if `include_docs` isn't
      ``true``. Default is ``false``.
    :query boolean att_encoding_info: Include encoding information in
      attachment stubs if `include_docs` is ``true`` and the particular
      attachment is compressed. Ignored if `include_docs` isn't ``true``.
      Default is ``false``.
    :query boolean inclusive_end: Specifies whether the specified end key
      should be included in the result. Default is ``true``
    :query json key: Return only documents that match the specified key.
      *Optional*
    :query json-array keys: Return only documents where the key matches one of
      the keys specified in the array. *Optional*
    :query number limit: Limit the number of the returned documents to the
      specified number. *Optional*
    :query boolean reduce: Use the reduction function. Default is ``true``
    :query number skip: Skip this number of records before starting to return
      the results. Default is ``0``
    :query boolean sorted: Sort returned rows (see :ref:`Sorting Returned Rows
     <api/ddoc/view/sorting>`). Setting this to ``false`` offers a performance
     boost. The `total_rows` and `offset` fields are not available when this
     is set to ``false``. Default is ``true``
    :query boolean stable: Whether or not the view results should be returned
     from a stable set of shards. Default is ``false``. *Optional*
    :query string stale: Allow the results from a stale view to be used.
      Supported values: ``ok``, ``update_after`` and ``false``.
      ``ok`` is equivalent to ``stable=true&update=false``.
      ``update_after`` is equivalent to ``stable=true&update=lazy``.
      ``false`` is equivalent to ``stable=false&update=true``.
      *Optional*
    :query json startkey: Return records starting with the specified key.
      *Optional*
    :query json start_key: Alias for `startkey` param
    :query string startkey_docid: Return records starting with the specified
      document ID. Requires ``startkey`` to be specified for this to have any
      effect. *Optional*
    :query string start_key_doc_id: Alias for `startkey_docid` param
    :query string update: Whether or not the view in question should be updated
     prior to responding to the user.
     Supported values: ``true``, ``false``, ``lazy``.
     Default is ``true``. *Optional*
    :query boolean update_seq: Response includes an ``update_seq`` value
      indicating which sequence id of the database the view reflects.
      Default is ``false``.

    :>header Content-Type: - :mimetype:`application/json`
                           - :mimetype:`text/plain; charset=utf-8`
    :>header ETag: Response signature
    :>header Transfer-Encoding: ``chunked``

    :>json number offset: Offset where the document list started
    :>json array rows: Array of view row objects. By default the information
      returned contains only the document ID and revision
    :>json number total_rows: Number of documents in the database/view
    :>json object update_seq: Current update sequence for the database

    :code 200: Request completed successfully
    :code 400: Invalid request
    :code 401: Read permission required
    :code 404: Specified database, design document or view is missed
    :code 500: View function execution error

    **Request**:

    .. code-block:: http

        GET /recipes/_design/ingredients/_view/by_name HTTP/1.1
        Accept: application/json
        Host: localhost:5984

    **Response**:

    .. code-block:: http

        HTTP/1.1 200 OK
        Cache-Control: must-revalidate
        Content-Type: application/json
        Date: Wed, 21 Aug 2013 09:12:06 GMT
        ETag: "2FOLSBSW4O6WB798XU4AQYA9B"
        Server: CouchDB (Erlang/OTP)
        Transfer-Encoding: chunked

        {
            "offset": 0,
            "rows": [
                {
                    "id": "SpaghettiWithMeatballs",
                    "key": "meatballs",
                    "value": 1
                },
                {
                    "id": "SpaghettiWithMeatballs",
                    "key": "spaghetti",
                    "value": 1
                },
                {
                    "id": "SpaghettiWithMeatballs",
                    "key": "tomato sauce",
                    "value": 1
                }
            ],
            "total_rows": 3
        }

.. versionchanged:: 1.6.0 added ``attachments`` and ``att_encoding_info``
    parameters
.. versionchanged:: 2.0.0 added ``sorted`` parameter
.. versionchanged:: 2.1.0 added ``stable`` and ``update`` parameters

.. warning::
    Using the ``attachments`` parameter to include attachments in view results
    is not recommended for large attachment sizes. Also note that the
    Base64-encoding that is used leads to a 33% overhead (i.e. one third) in
    transfer size for attachments.

.. http:post:: /{db}/_design/{ddoc}/_view/{view}
    :synopsis: Returns certain rows for the specified stored view

    Executes the specified view function from the specified design document.
    Unlike :get:`/{db}/_design/{ddoc}/_view/{view}` for accessing views, the
    :method:`POST` method supports the specification
    of explicit keys to be retrieved from the view results. The remainder of
    the :method:`POST` view functionality is identical to the
    :get:`/{db}/_design/{ddoc}/_view/{view}` API.

    **Request**:

    .. code-block:: http

        POST /recipes/_design/ingredients/_view/by_name HTTP/1.1
        Accept: application/json
        Content-Length: 37
        Host: localhost:5984

        {
            "keys": [
                "meatballs",
                "spaghetti"
            ]
        }

    **Response**:

    .. code-block:: http

        HTTP/1.1 200 OK
        Cache-Control: must-revalidate
        Content-Type: application/json
        Date: Wed, 21 Aug 2013 09:14:13 GMT
        ETag: "6R5NM8E872JIJF796VF7WI3FZ"
        Server: CouchDB (Erlang/OTP)
        Transfer-Encoding: chunked

        {
            "offset": 0,
            "rows": [
                {
                    "id": "SpaghettiWithMeatballs",
                    "key": "meatballs",
                    "value": 1
                },
                {
                    "id": "SpaghettiWithMeatballs",
                    "key": "spaghetti",
                    "value": 1
                }
            ],
            "total_rows": 3
        }

.. _api/ddoc/view/options:

View Options
============

There are two view indexing options that can be defined in a design document
as boolean properties of an ``options`` object. Unlike the others querying
options, these aren't URL parameters because they take effect when the view
index is generated, not when it's accessed:

- **local_seq** (*boolean*): Makes documents' local sequence numbers available
  to map functions (as a ``_local_seq`` document property)
- **include_design** (*boolean*): Allows map functions to be called on design
  documents as well as regular documents

.. _api/ddoc/view/indexing:

Querying Views and Indexes
==========================

The definition of a view within a design document also creates an index based
on the key information defined within each view. The production and use of the
index significantly increases the speed of access and searching or selecting
documents from the view.

However, the index is not updated when new documents are added or modified in
the database. Instead, the index is generated or updated, either when the view
is first accessed, or when the view is accessed after a document has been
updated. In each case, the index is updated before the view query is executed
against the database.

View indexes are updated incrementally in the following situations:

- A new document has been added to the database.
- A document has been deleted from the database.
- A document in the database has been updated.

View indexes are rebuilt entirely when the view definition changes. To achieve
this, a 'fingerprint' of the view definition is created when the design
document is updated. If the fingerprint changes, then the view indexes are
entirely rebuilt. This ensures that changes to the view definitions are
reflected in the view indexes.

.. note::
    View index rebuilds occur when one view from the same the view group (i.e.
    all the views defined within a single a design document) has been
    determined as needing a rebuild. For example, if if you have a design
    document with different views, and you update the database, all three view
    indexes within the design document will be updated.

Because the view is updated when it has been queried, it can result in a delay
in returned information when the view is accessed, especially if there are a
large number of documents in the database and the view index does not exist.
There are a number of ways to mitigate, but not completely eliminate, these
issues. These include:

- Create the view definition (and associated design documents) on your database
  before allowing insertion or updates to the documents. If this is allowed
  while the view is being accessed, the index can be updated incrementally.

- Manually force a view request from the database. You can do this either
  before users are allowed to use the view, or you can access the view manually
  after documents are added or updated.

- Use the :ref:`changes feed <api/db/changes>` to monitor for changes to the
  database and then access the view to force the corresponding view index to be
  updated.

- Use a monitor with the :ref:`update notification <update-notifications>`
  section of the CouchDB configuration file to monitor for changes to your
  database, and trigger a view query to force the view to be updated.

None of these can completely eliminate the need for the indexes to be rebuilt
or updated when the view is accessed, but they may lessen the effects on
end-users of the index update affecting the user experience.

Another alternative is to allow users to access a 'stale' version of the view
index, rather than forcing the index to be updated and displaying the updated
results. Using a stale view may not return the latest information, but will
return the results of the view query using an existing version of the index.

For example, to access the existing stale view ``by_recipe`` in the
``recipes`` design document:

.. code-block:: text

    http://localhost:5984/recipes/_design/recipes/_view/by_recipe?stale=ok

Accessing a stale view:

- Does not trigger a rebuild of the view indexes, even if there have been
  changes since the last access.

- Returns the current version of the view index, if a current version exists.

- Returns an empty result set if the given view index does exist.

As an alternative, you use the ``update_after`` value to the ``stale``
parameter. This causes the view to be returned as a stale view, but for the
update process to be triggered after the view information has been returned to
the client.

In addition to using stale views, you can also make use of the ``update_seq``
query argument. Using this query argument generates the view information
including the update sequence of the database from which the view was
generated. The returned value can be compared this to the current update
sequence exposed in the database information (returned by :get:`/{db}`).

.. _api/ddoc/view/sorting:

Sorting Returned Rows
=====================

Each element within the returned array is sorted using native UTF-8 sorting
according to the contents of the key portion of the emitted content. The basic
order of output is as follows:

-  ``null``
-  ``false``
-  ``true``
-  Numbers
-  Text (case sensitive, lowercase first)
-  Arrays (according to the values of each element, in order)
-  Objects (according to the values of keys, in key order)

**Request**:

.. code-block:: http

    GET /db/_design/test/_view/sorting HTTP/1.1
    Accept: application/json
    Host: localhost:5984

**Response**:

.. code-block:: http

    HTTP/1.1 200 OK
    Cache-Control: must-revalidate
    Content-Type: application/json
    Date: Wed, 21 Aug 2013 10:09:25 GMT
    ETag: "8LA1LZPQ37B6R9U8BK9BGQH27"
    Server: CouchDB (Erlang/OTP)
    Transfer-Encoding: chunked

    {
        "offset": 0,
        "rows": [
            {
                "id": "dummy-doc",
                "key": null,
                "value": null
            },
            {
                "id": "dummy-doc",
                "key": false,
                "value": null
            },
            {
                "id": "dummy-doc",
                "key": true,
                "value": null
            },
            {
                "id": "dummy-doc",
                "key": 0,
                "value": null
            },
            {
                "id": "dummy-doc",
                "key": 1,
                "value": null
            },
            {
                "id": "dummy-doc",
                "key": 10,
                "value": null
            },
            {
                "id": "dummy-doc",
                "key": 42,
                "value": null
            },
            {
                "id": "dummy-doc",
                "key": "10",
                "value": null
            },
            {
                "id": "dummy-doc",
                "key": "hello",
                "value": null
            },
            {
                "id": "dummy-doc",
                "key": "Hello",
                "value": null
            },
            {
                "id": "dummy-doc",
                "key": "\u043f\u0440\u0438\u0432\u0435\u0442",
                "value": null
            },
            {
                "id": "dummy-doc",
                "key": [],
                "value": null
            },
            {
                "id": "dummy-doc",
                "key": [
                    1,
                    2,
                    3
                ],
                "value": null
            },
            {
                "id": "dummy-doc",
                "key": [
                    2,
                    3
                ],
                "value": null
            },
            {
                "id": "dummy-doc",
                "key": [
                    3
                ],
                "value": null
            },
            {
                "id": "dummy-doc",
                "key": {},
                "value": null
            },
            {
                "id": "dummy-doc",
                "key": {
                    "foo": "bar"
                },
                "value": null
            }
        ],
        "total_rows": 17
    }

You can reverse the order of the returned view information by using the
``descending`` query value set to true:

**Request**:

.. code-block:: http

    GET /db/_design/test/_view/sorting?descending=true HTTP/1.1
    Accept: application/json
    Host: localhost:5984

**Response**:

.. code-block:: http

    HTTP/1.1 200 OK
    Cache-Control: must-revalidate
    Content-Type: application/json
    Date: Wed, 21 Aug 2013 10:09:25 GMT
    ETag: "Z4N468R15JBT98OM0AMNSR8U"
    Server: CouchDB (Erlang/OTP)
    Transfer-Encoding: chunked

    {
        "offset": 0,
        "rows": [
            {
                "id": "dummy-doc",
                "key": {
                    "foo": "bar"
                },
                "value": null
            },
            {
                "id": "dummy-doc",
                "key": {},
                "value": null
            },
            {
                "id": "dummy-doc",
                "key": [
                    3
                ],
                "value": null
            },
            {
                "id": "dummy-doc",
                "key": [
                    2,
                    3
                ],
                "value": null
            },
            {
                "id": "dummy-doc",
                "key": [
                    1,
                    2,
                    3
                ],
                "value": null
            },
            {
                "id": "dummy-doc",
                "key": [],
                "value": null
            },
            {
                "id": "dummy-doc",
                "key": "\u043f\u0440\u0438\u0432\u0435\u0442",
                "value": null
            },
            {
                "id": "dummy-doc",
                "key": "Hello",
                "value": null
            },
            {
                "id": "dummy-doc",
                "key": "hello",
                "value": null
            },
            {
                "id": "dummy-doc",
                "key": "10",
                "value": null
            },
            {
                "id": "dummy-doc",
                "key": 42,
                "value": null
            },
            {
                "id": "dummy-doc",
                "key": 10,
                "value": null
            },
            {
                "id": "dummy-doc",
                "key": 1,
                "value": null
            },
            {
                "id": "dummy-doc",
                "key": 0,
                "value": null
            },
            {
                "id": "dummy-doc",
                "key": true,
                "value": null
            },
            {
                "id": "dummy-doc",
                "key": false,
                "value": null
            },
            {
                "id": "dummy-doc",
                "key": null,
                "value": null
            }
        ],
        "total_rows": 17
    }

Sorting order and startkey/endkey
---------------------------------

The sorting direction is applied before the filtering applied using the
``startkey`` and ``endkey`` query arguments. For example the following query:

.. code-block:: http

    GET http://couchdb:5984/recipes/_design/recipes/_view/by_ingredient?startkey=%22carrots%22&endkey=%22egg%22 HTTP/1.1
    Accept: application/json

will operate correctly when listing all the matching entries between
``carrots`` and ``egg``. If the order of output is reversed with the
``descending`` query argument, the view request will return no entries:

.. code-block:: http

    GET /recipes/_design/recipes/_view/by_ingredient?descending=true&startkey=%22carrots%22&endkey=%22egg%22 HTTP/1.1
    Accept: application/json
    Host: localhost:5984

    {
        "total_rows" : 26453,
        "rows" : [],
        "offset" : 21882
    }

The results will be empty because the entries in the view are reversed before
the key filter is applied, and therefore the ``endkey`` of “egg” will be seen
before the ``startkey`` of “carrots”, resulting in an empty list.

Instead, you should reverse the values supplied to the ``startkey`` and
``endkey`` parameters to match the descending sorting applied to the keys.
Changing the previous example to:

.. code-block:: http

    GET /recipes/_design/recipes/_view/by_ingredient?descending=true&startkey=%22egg%22&endkey=%22carrots%22 HTTP/1.1
    Accept: application/json
    Host: localhost:5984

.. _api/ddoc/view/sorting/raw:

Raw collation
-------------

By default CouchDB using `ICU`_ driver for sorting view results. It's possible
use binary collation instead for faster view builds where Unicode collation is
not important.

To use raw collation add ``"collation": "raw"`` key-value pair to the design
documents ``options`` object at the root level. After that, views will be
regenerated and new order applied.

.. seealso::
    :ref:`views/collation`

.. _ICU: http://site.icu-project.org/

.. _api/ddoc/view/limiting:

Using Limits and Skipping Rows
==============================

By default, views return all results. That's ok when the number of results is
small, but this may lead to problems when there are billions results, since the
client may have to read them all and consume all available memory.

But it's possible to reduce output result rows by specifying ``limit`` query
parameter. For example, retrieving the list of recipes using the ``by_title``
view and limited to 5 returns only 5 records, while there are total 2667
records in view:

**Request**:

.. code-block:: http

    GET /recipes/_design/recipes/_view/by_title?limit=5 HTTP/1.1
    Accept: application/json
    Host: localhost:5984

**Response**:

.. code-block:: http

    HTTP/1.1 200 OK
    Cache-Control: must-revalidate
    Content-Type: application/json
    Date: Wed, 21 Aug 2013 09:14:13 GMT
    ETag: "9Q6Q2GZKPH8D5F8L7PB6DBSS9"
    Server: CouchDB (Erlang/OTP)
    Transfer-Encoding: chunked

    {
        "offset" : 0,
        "rows" : [
            {
                "id" : "3-tiersalmonspinachandavocadoterrine",
                "key" : "3-tier salmon, spinach and avocado terrine",
                "value" : [
                    null,
                    "3-tier salmon, spinach and avocado terrine"
                ]
            },
            {
                "id" : "Aberffrawcake",
                "key" : "Aberffraw cake",
                "value" : [
                    null,
                    "Aberffraw cake"
                ]
            },
            {
                "id" : "Adukiandorangecasserole-microwave",
                "key" : "Aduki and orange casserole - microwave",
                "value" : [
                    null,
                    "Aduki and orange casserole - microwave"
                ]
            },
            {
                "id" : "Aioli-garlicmayonnaise",
                "key" : "Aioli - garlic mayonnaise",
                "value" : [
                    null,
                    "Aioli - garlic mayonnaise"
                ]
            },
            {
                "id" : "Alabamapeanutchicken",
                "key" : "Alabama peanut chicken",
                "value" : [
                    null,
                    "Alabama peanut chicken"
                ]
            }
        ],
        "total_rows" : 2667
    }

To omit some records you may use ``skip`` query parameter:

**Request**:

.. code-block:: http

    GET /recipes/_design/recipes/_view/by_title?limit=3&skip=2 HTTP/1.1
    Accept: application/json
    Host: localhost:5984

**Response**:

.. code-block:: http

    HTTP/1.1 200 OK
    Cache-Control: must-revalidate
    Content-Type: application/json
    Date: Wed, 21 Aug 2013 09:14:13 GMT
    ETag: "H3G7YZSNIVRRHO5FXPE16NJHN"
    Server: CouchDB (Erlang/OTP)
    Transfer-Encoding: chunked

    {
        "offset" : 2,
        "rows" : [
            {
                "id" : "Adukiandorangecasserole-microwave",
                "key" : "Aduki and orange casserole - microwave",
                "value" : [
                    null,
                    "Aduki and orange casserole - microwave"
                ]
            },
            {
                "id" : "Aioli-garlicmayonnaise",
                "key" : "Aioli - garlic mayonnaise",
                "value" : [
                    null,
                    "Aioli - garlic mayonnaise"
                ]
            },
            {
                "id" : "Alabamapeanutchicken",
                "key" : "Alabama peanut chicken",
                "value" : [
                    null,
                    "Alabama peanut chicken"
                ]
            }
        ],
        "total_rows" : 2667
    }

.. warning::
    Using ``limit`` and ``skip`` parameters is not recommended for results
    pagination. Read :ref:`pagination recipe <views/pagination>` why it's so
    and how to make it better.

.. _api/ddoc/view/multiple_queries:

Sending multiple queries to a view
==================================

.. versionadded:: 2.0

.. http:post:: /{db}/_design/{ddoc}/_view/{view}
    :synopsis: Returns results for the specified queries

    Executes multiple specified view queries against the view function
    from the specified design document.

    :param db: Database name
    :param ddoc: Design document name
    :param view: View function name

    :<header Content-Type: - :mimetype:`application/json`
    :<header Accept: - :mimetype:`application/json`
                     - :mimetype:`text/plain`

    :query json queries: An array of query objects with fields for the
        parameters of each individual view query to be executed. The field names
        and their meaning are the same as the query parameters of a
        regular :ref:`view request <api/ddoc/view>`.

    :>header Content-Type: - :mimetype:`application/json`
                           - :mimetype:`text/plain; charset=utf-8`
    :>header ETag: Response signature
    :>header Transfer-Encoding: ``chunked``

    :>json array results: An array of result objects - one for each query. Each
        result object contains the same fields as the response to a regular
        :ref:`view request <api/ddoc/view>`.

    :code 200: Request completed successfully
    :code 400: Invalid request
    :code 401: Read permission required
    :code 404: Specified database, design document or view is missed
    :code 500: View function execution error

**Request**:

.. code-block:: http

    POST /recipes/_design/recipes/_view/by_title HTTP/1.1
    Content-Type: application/json
    Accept: application/json
    Host: localhost:5984

    {
        "queries": [
            {
                "keys": [
                    "meatballs",
                    "spaghetti"
                ]
            },
            {
                "limit": 3,
                "skip": 2
            }
        ]
    }

**Response**:

.. code-block:: http

    HTTP/1.1 200 OK
    Cache-Control: must-revalidate
    Content-Type: application/json
    Date: Wed, 07 Sep 2016 11:17:07 GMT
    ETag: "1H8RGBCK3ABY6ACDM7ZSC30QK"
    Server: CouchDB (Erlang/OTP)
    Transfer-Encoding: chunked

    {
        "results" : [
            {
                "offset": 0,
                "rows": [
                    {
                        "id": "SpaghettiWithMeatballs",
                        "key": "meatballs",
                        "value": 1
                    },
                    {
                        "id": "SpaghettiWithMeatballs",
                        "key": "spaghetti",
                        "value": 1
                    },
                    {
                        "id": "SpaghettiWithMeatballs",
                        "key": "tomato sauce",
                        "value": 1
                    }
                ],
                "total_rows": 3
            },
            {
                "offset" : 2,
                "rows" : [
                    {
                        "id" : "Adukiandorangecasserole-microwave",
                        "key" : "Aduki and orange casserole - microwave",
                        "value" : [
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