On Thu, Jan 03, 2019 at 01:02:57PM -0500, David Davis wrote: > I don't think that using integer ids with bulk_create and supporting > mysql/mariadb are necessarily mutually exclusive. I think there might > be a way to find the records created using bulk_create if we know the > natural key. It might be more performant than using UUIDs as well.
This assumes that there is a natural key. For content types with no digest information in the meta data, there may be a natural key for content within a repo version only, but no natural key for the overall content. (If we want to support non-immediate modes for such content. In immediate mode, a digest can be computed from the associated artifact(s)). Of course, there are ways around that (use a UUID as the "natural" key, or add a UUID to the repo version key fields), but I would like to avoid that. > On Thu, Jan 3, 2019 at 11:04 AM Dennis Kliban <[1]dkli...@redhat.com> > wrote: > > Thank you Daniel for the explanation and for filing an issue[0] to do > performance analysis of UUIDs. > I really hope that we can switch back to using UUIDs so we can bring > back MariaDB support for Pulp 3. > [0] [2]https://pulp.plan.io/issues/4290 > > On Wed, Dec 5, 2018 at 1:35 PM Daniel Alley <[3]dal...@redhat.com> > wrote: > > To rephrase the problem a little bit: > We need to bulk_create() a bunch of objects, and then after we do that > we want to immediately be able to relate them with other objects, which > means we need their PKs of the objects that were just created. > In the case of auto-increment integer PKs, we can't know that PK value > before it gets saved into the database. Luckily, PostgreSQL (and > Oracle) support a "RETURNING" keyword that does provides this > information. The raw SQL would look something like this: > > INSERT INTO items (name) values ('bear') RETURNING id; > > Django uses this feature to set the PK field on the model objects it > returns when you call bulk_create() on a list of unsaved model objects. > Unfortunately, MySQL doesn't support this, so there's no way to figure > out what the PKs of the objects you just saved were, so the ORM can't > set that information on the returned model objects. > UUID PKs circumvent this because the PK gets created outside of the > database, prior to being saved in the database, and so Django *can* > know what the PK will be when it gets saved. > > On Wed, Dec 5, 2018 at 12:11 PM Brian Bouterse <[4]bbout...@redhat.com> > wrote: > > +1 to experimentation and also making sure that we understand the > performance implications of the decision. I'm replying to this earlier > note to restate my observations of the problem a bit more. > More ideas and thoughts are welcome. This is a decision with a lot of > aspects to consider. > On Tue, Nov 20, 2018 at 10:00 AM Patrick Creech <[5]pcre...@redhat.com> > wrote: > > On Mon, 2018-11-19 at 17:08 -0500, Brian Bouterse wrote: > > When we switched from UUID to integers for the PK > > with databases other than PostgreSQL [0]. > > > > With a goal of database agnosticism for Pulp3, if plugin writers > plan to use bulk_create with any object inherited > > from one of ours, they can't will get different behaviors on > different databases and they won't have PKs that they may > > require. bulk_create is a normal django thing, so plugin writers > making a django plugin should be able to use it. This > > concerned me already, but today it was also brought up by non-RH > plugin writers also [1] in a PR. > > > > The tradeoffs bteween UUIDs versus PKs are pretty well summed up > in our ticket where we discussed that change [2]. > > Note, we did not consider this bulk_create downside at that time, > which I think is the most significant downside to > > consider. > > > > Having bulk_create effectively not available for plugin writers > (since we can't rely on its pks being returned) I > > think is a non-starter for me. I love how short the UUIDs made our > URLs so that's the tradeoff mainly in my mind. > > Those balanced against each other, I think we should switch back. > > > > Another option is to become PostgreSQL only which (though I love > psql) I think would be the wrong choice for Pulp from > > what I've heard from its users. > > > > What do you think? What should we do? > So, my mind immediately goes to this question, which might be > usefull for others to help make decisions, so I'll ask: > When you say: > "we lost the ability to have the primary key set during bulk_create" > Can you clarify what you mean by this? > My mind immediately goes to this chain of events: > When you use bulk_create, the existing in-memory model > objects representing the data to create do not get > updated with the primary key values that are created in the > database. > Upon a subsequent query of the database, for the exact same > set of objects just added, those objects _will_ have > the primary key populated. > In other words, > The database records themselves get the auto-increment IDs > added, they just don't get reported back in that > query to the ORM layer, therefore it takes a subsequent query to get > those ids out. > Does that about sum it up? > > Yes this describes the situation, but there is a bit more to tell. > Since PostgreSQL does return the ids the subsequent query that could be > done to get the ids isn't written in code today. We didn't need to > because we developed it against PostgreSQL. I'm pretty sure that if you > configure Pulp against MySQL Pulp won't work, which I think is a > problem. So I'm observing two things here. 1) This is a hazard that > causes code to unexpectedly be only compliant with PostgreSQL. 2) Pulp > itself fell into this hazard and we need to fix that too > Do you also see these two issues? What should be done about these? > > > > > [0]: > [6]https://docs.djangoproject.com/en/2.1/ref/models/querysets/#bulk- > create > > [1]: > [7]https://github.com/pulp/pulp/pull/3764#discussion_r234780702 > > [2]: [8]https://pulp.plan.io/issues/3848 > > _______________________________________________ > > Pulp-dev mailing list > > [9]Pulp-dev@redhat.com > > [10]https://www.redhat.com/mailman/listinfo/pulp-dev > _______________________________________________ > Pulp-dev mailing list > [11]Pulp-dev@redhat.com > [12]https://www.redhat.com/mailman/listinfo/pulp-dev > > _______________________________________________ > Pulp-dev mailing list > [13]Pulp-dev@redhat.com > [14]https://www.redhat.com/mailman/listinfo/pulp-dev > > _______________________________________________ > Pulp-dev mailing list > [15]Pulp-dev@redhat.com > [16]https://www.redhat.com/mailman/listinfo/pulp-dev > > _______________________________________________ > Pulp-dev mailing list > [17]Pulp-dev@redhat.com > [18]https://www.redhat.com/mailman/listinfo/pulp-dev > > References > > 1. mailto:dkli...@redhat.com > 2. https://pulp.plan.io/issues/4290 > 3. mailto:dal...@redhat.com > 4. mailto:bbout...@redhat.com > 5. mailto:pcre...@redhat.com > 6. https://docs.djangoproject.com/en/2.1/ref/models/querysets/#bulk-create > 7. https://github.com/pulp/pulp/pull/3764#discussion_r234780702 > 8. https://pulp.plan.io/issues/3848 > 9. mailto:Pulp-dev@redhat.com > 10. https://www.redhat.com/mailman/listinfo/pulp-dev > 11. mailto:Pulp-dev@redhat.com > 12. https://www.redhat.com/mailman/listinfo/pulp-dev > 13. mailto:Pulp-dev@redhat.com > 14. https://www.redhat.com/mailman/listinfo/pulp-dev > 15. mailto:Pulp-dev@redhat.com > 16. https://www.redhat.com/mailman/listinfo/pulp-dev > 17. mailto:Pulp-dev@redhat.com > 18. https://www.redhat.com/mailman/listinfo/pulp-dev > _______________________________________________ > Pulp-dev mailing list > Pulp-dev@redhat.com > https://www.redhat.com/mailman/listinfo/pulp-dev -- Simon Baatz <gmbno...@gmail.com> _______________________________________________ Pulp-dev mailing list Pulp-dev@redhat.com https://www.redhat.com/mailman/listinfo/pulp-dev
