Glance sorting API specification
This spec describes new sorting standard for image output in Glance and defines the system behavior in different cases. Also information about sorting and some examples were added to the existing api listing spec. Change-Id: Ic1181d9d581492ce34e75b7e78a1a56813c0aaaf
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Mike Fedosin
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@ -40,11 +40,75 @@ only images that are between one and four megabytes in size.
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**Sorting**
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The results of this operation can be ordered using the 'sort\_key' and
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'sort\_dir' parameters. The API uses the natural sorting of whatever
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image attribute is provided as the 'sort\_key'. All image attributes can
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be used as the sort\_key (except tags and link attributes). The
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sort\_dir parameter indicates in which direction to sort. Acceptable
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values are 'asc' (ascending) and 'desc' (descending). Defaults values
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for sort\_key and sort\_dir are 'created\_at' and 'desc'.
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The results of this operation can be ordered by using classic and new
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sorting syntaxes. Classic syntax uses multiple 'sort\_key' and
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'sort\_dir' parameters, and new one accepts a single 'sort' string with
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comma separated sort keys with optional sort direction after ':'.
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Both syntaxes provide an ability to sort output with multiple keys and
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directions but with some differences.
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The classic syntax takes a list of keys and either exactly the same
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number of directions for each key, or only one that specifies the
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default value for all keys.
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The new syntax applies a default direction to all keys where it's
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missing.
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The API uses the natural sorting of whatever image attribute is
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provided as the sort key. List of image attributes can be used as the
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sort key: 'name', 'status', 'container\_format', 'disk\_format',
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'size', 'id', 'created\_at', 'updated\_at'. The sort dir parameter
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indicates in which direction to sort. Acceptable values are 'asc'
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(ascending) and 'desc' (descending). Default values for sort key and
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sort direction are 'created\_at' and 'desc'.
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Examples of sorting:
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#. New syntax with specified direction for keys::
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sort=name:asc,status:asc
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Sort: by name with asc order, then by status with asc order.
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#. New syntax with missing direction::
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sort=name,status:asc
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Sort: by name with desc order, then by status with asc order.
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#. New syntax without directions::
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sort=name,status
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Sort: by name with desc order, then by status with desc order.
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#. Classic syntax with specified default direction::
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sort_key=name&sort_key=status&sort_dir=asc
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Sort: by name with asc order, then by status with asc order.
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#. Classic syntax with missing direction::
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sort_key=name&sort_key=status
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Sort: by name with desc order, then by status with desc order.
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#. Classic syntax with missing key and specified default direction::
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sort_dir=asc
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Sort: by created_at with asc order.
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#. Classic syntax with specified direction for keys::
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sort_key=name&sort_dir=desc&sort_key=status&sort_dir=asc
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Sort: by name with desc order, then by status with asc order.
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#. Classic syntax with different number of keys and directions::
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sort_key=name&sort_dir=asc&sort_key=status&sort_dir=asc&sort_key=id
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Will be an error.
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244
specs/kilo/sorting-enhancements.rst
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244
specs/kilo/sorting-enhancements.rst
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@ -0,0 +1,244 @@
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..
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This work is licensed under a Creative Commons Attribution 3.0 Unported
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License.
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http://creativecommons.org/licenses/by/3.0/legalcode
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Glance sorting enhancements
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===========================
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https://blueprints.launchpad.net/glance/+spec/glance-sorting-enhancements
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Currently, the sorting support for Glance allows the caller to specify
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multiple sort keys and one sort direction. This blueprint enhances the
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sorting support for the /images and /images/detail APIs so that
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multiple sort keys and sort directions can be supplied on the request.
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Problem description
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~~~~~~~~~~~~~~~~~~~
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There is no support for retrieving image data based on multiple sort
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directions; multiple sort keys and one direction are currently
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supported, and they're defaulted to descending sort order by the
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"created_at" key.
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In order to retrieve data in any sort order and direction, the REST
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APIs need to accept multiple sort keys and directions.
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Use Case: A UI that displays a table with only the page of data that it
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has retrieved from the server. The items in this table need to be sorted
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by status first and by display name second. In order to retrieve data in
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this order, the APIs must accept multiple sort keys/directions.
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Proposed change
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~~~~~~~~~~~~~~~~~~~
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The /images and /images/detail APIs will align with the API working group
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guidelines [1]_ for sorting and support the following parameter on the
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request:
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* sort: Comma-separated list of sort keys, each key is optionally appended
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with <:dir>, where 'dir' is the direction for the corresponding sort key
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(supported values are 'asc' for ascending and 'desc' for descending).
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For example::
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/images?sort=status:asc,name:asc,created_at:desc
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Note: The "created_at" and "id" sort keys are always appended at the end of
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the key list if they are not already specified in the request.
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The database layer already supports multiple sort keys and directions. This
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blueprint will update the API layer to retrieve the sort information from
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the API request and pass that information down to the database layer.
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All sorting is handled in the glance.db.sqlalchemy.api._paginate_query
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function. This function accepts an ORM model class as an argument and the
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only valid sort keys are attributes on the given model class. Therefore,
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the valid sort keys are: 'name', 'status', 'container_format', 'disk_format',
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'size', 'id', 'created_at', 'updated_at'.
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Alternatives
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------------
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Multiple sort keys and directions could be passed using repeated 'sort_key'
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and 'sort_dir' query parameters. For example::
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/images?sort_key=status&sort_dir=asc&sort_key=name&sort_dir=asc&
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sort_key=created_at&sort_dir=desc
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To provide users with the ability to use the classic familiar syntax and to
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ensure a smoother transition to the new one, classic syntax should be
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implemented too.
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Data model impact
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-----------------
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None
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REST API impact
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---------------
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The following existing v2 GET APIs will support the new sorting parameters:
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* /v2/images
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* /v2/images/detail
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Note that the design described in this blueprint could be applied to other GET
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REST APIs, but this blueprint is scoped to only those listed above. Once this
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design is finalized, then the same approach could be applied to other APIs.
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The existing API documentation needs to be updated to include the following
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new Request Parameters:
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+-----------+-------+--------+------------------------------------------------+
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| Parameter | Style | Type | Description |
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+===========+=======+========+================================================+
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| sort | query | string | Comma-separated list of sort keys and optional |
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| | | | sort directions in the form of key<:dir>, |
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| | | | where 'dir' is either 'asc' for ascending |
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| | | | order or 'desc' for descending order. Defaults |
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| | | | to the 'created_at' and 'id' keys in |
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| | | | descending order. |
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+-----------+-------+--------+------------------------------------------------+
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Currently, the images query supports the 'sort_key' and 'sort_dir' parameters;
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these will be deprecated. The API will raise a "BadRequest" error response
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(code 400) if both the new 'sort' parameter and a deprecated 'sort_key' or
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'sort_dir' parameter is specified.
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Neither the API response format nor the return codes will be modified, only
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the order of the images that are returned.
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In the event that an invalid sort key or sort direction is specified, then a
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"BadRequest" error response (code 400) will be returned with a message like
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"Invalid input received: Invalid sort key" or "Invalid input received: Invalid
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sort dir" respectively.
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Security impact
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---------------
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None
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Notifications impact
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--------------------
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None
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Other end user impact
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---------------------
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The python-glanceclient should be updated to accept sort keys and
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sort directions, using the 'sort' parameter being proposed in the
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cross-project spec [2]_.
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Performance Impact
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------------------
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None
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Other deployer impact
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---------------------
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The choice of sort keys has no impact on data retrieval performance.
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Therefore, the user should be allowed to retrieve data in whatever
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order they need to for creating their views (see use case in the
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Problem Description).
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Developer impact
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----------------
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None
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Implementation
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~~~~~~~~~~~~~~
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Assignee(s)
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-----------
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Primary assignee:
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mfedosin
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Other contributors:
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None
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Reviewers
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---------
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ativelkov
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icordasc
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nikhil-komawar
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Work Items
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----------
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Ideally the logic for processing the sort parameters would be common to all
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components and would be done in oslo; a similar blueprint is also being
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proposed in nova:
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https://blueprints.launchpad.net/nova/+spec/nova-pagination
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Therefore, I see the following work items:
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* Update the existing API to retrieve the sort information and pass down to
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the DB layer (https://review.openstack.org/#/c/148326/);
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* Extend API with new syntax to support multiple sorting keys and directions
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(https://review.openstack.org/#/c/148512/);
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* Update the python-glanceclient to accept and process multiple sort keys and
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sort directions with classic and new sorting syntax
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(https://review.openstack.org/#/c/120777/,
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https://review.openstack.org/#/c/148688/,
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https://review.openstack.org/#/c/148981/);
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* Implement the full test coverage for the new changes.
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Dependencies
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~~~~~~~~~~~~
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* CLI Sorting Argument Guidelines cross project spec [2]_;
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* Related (but independent) change being proposed in nova [3]_.
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Testing
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~~~~~~~
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Both unit and Tempest tests need to be created to ensure that the data is
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retrieved in the specified sort order. Tests should also verify that the
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default sort keys ("created_at" and "id") are always appended to the user
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supplied keys (if the user did not already specify them).
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Documentation Impact
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~~~~~~~~~~~~~~~~~~~~
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The /images and /images/detail API documentation will need to be updated
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to:
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- reflect the new sorting parameters and explain that these parameters will
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affect the order in which the data is returned.
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- explain how the default sort keys will always be added at the end of the
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sort key list.
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References
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~~~~~~~~~~
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.. [1]
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`API Working group sorting guidelines <https://github.com/openstack/
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api-wg/blob/master/guidelines/pagination_filter_sort.rst>`_
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.. [2]
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`CLI Sorting Argument Guidelines <http://specs.openstack.org/openstack/
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openstack-specs/specs/cli-sorting-args.html>`_
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.. [3]
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`Related change being proposed in nova <https://blueprints.launchpad.net/
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nova/+spec/nova-pagination>`_
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