[Pulp-dev] uniqueness constraints within a repository version

[Brian Bouterse]

Having a way for units to express their uniqueness per repo sounds good
because then more areas of Pulp's code could answer the question: "will I
have a duplicate if I add content X to repo_version Y".

Let's assume we know that situation is about to occur during sync for
example, what do we do about it? In the errata case we know the "new" one
should replace the existing one. Maybe we start to 'order' the units with
colliding repo keys and keep the newest one always? Would this work for
pulp_cookbook and pulp_rpm? Would it generalize? Is this what you imagined?

On Tue, Jun 25, 2019 at 5:30 AM Tatiana Tereshchenko <ttereshc at redhat.com>
wrote:

> Do I understand correctly that it doesn't cover the sync case and it's
> only about explicit repo version creation?
> So the suggestion is to implement the same logic twice: for sync case -
> RemoveDuplicates stage and/or maybe some custom stage (e.g. to disallow
> overlapping paths), and for direct repo version creation - your proposal.
>
>
>
> On Mon, Jun 24, 2019 at 3:13 PM Austin Macdonald <amacdona at redhat.com>
> wrote:
>
>> I have a design in mind for solving this problem:
>>
>> 1. Remove POST to RepositoryVersion (no general add/remove endpoint).
>> 2. Add an endpoint to kick off an add/remove task, namespaced by plugin.
>> ie `POST pulp/api/v3/docker/add-remove/`
>>    This view can be provided to all plugins by the plugin template, and
>> will be based on the current RepositoryVersionCreate:
>>
>> https://github.com/pulp/pulpcore/blob/master/pulpcore/app/viewsets/repository.py#L221-L258
>>    Note: the main purpose of this view is to kick off the general
>> add/remove task, which will be unchanged:
>>
>> https://github.com/pulp/pulpcore/blob/master/pulpcore/app/tasks/repository.py#L70
>> 3. Add an add/remove serializer to the plugin API.
>> 3. Plugins needing further customization can provide their own task and
>> subclassed serializer.
>>
>> This gives the plugin writer full control over the endpoint (customizable
>> arguments and validation), and full control over the flow (extra logic,
>> depsolving, enforced uniqueness). It only uses the existing patterns (and
>> existing required knowledge), but requires no work (other than using the
>> template) for the simple case.
>>
>> On Mon, Jun 3, 2019 at 2:56 PM Simon Baatz <gmbnomis at gmail.com> wrote:
>>
>>> On Mon, Jun 03, 2019 at 09:11:07AM -0400, David Davis wrote:
>>> >    @Simon I like the idea behind the repo_key solution you came up
>>> with.
>>> >    Can you be more specific around cases you think that it couldn't
>>> >    handle? I imagine that plugin writers could use properties or
>>> >    denormailzation (ie additional database columns) to solve cases
>>> where
>>> >    they need uniqueness across data that isn't in the database. In a
>>> worst
>>> >    case scenario, they can't use the pulpcore solution and just have to
>>> >    roll their own.
>>>
>>>
>>> What I wrote probably sounded too pessimistic. You are right, in
>>> most cases that should be doable.
>>>
>>> I agree that we could have a simple default solution that just
>>> requires to specify a couple of field names in the easiest case.  As you
>>> say, it should be possible use custom logic in a plugin if required.
>>>
>>> Here is the case I was thinking of that it can't handle:
>>>
>>> In pulp_file, a uniqueness constraint on "relative_path" would allow
>>> content units "a" and "a/b" to be in a repo version.
>>>
>>> However, we may want file repos to be representable on an actual file
>>> system (e.g. when exporting them as tar files).  For the repo above,
>>> this does not work, as "a" can't be a file and a directory at the
>>> same time on a standard Unix file system.
>>>
>>>
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