Since there seems to be no objections to switching to UUIDs, I’d like to propose we merge the PRs[0][1] that will switch core to use UUID PKs tomorrow (in 24 hours). After that, we'll open redmine issues to update plugins to use UUIDs.
[0] https://github.com/pulp/pulpcore/pull/16 [1] https://github.com/pulp/pulpcore-plugin/pull/69 David On Tue, Mar 5, 2019 at 5:15 PM Jeff Ortel <[email protected]> wrote: > +1 to switching back to UUIDs for the reasons Brian gave. > > On 3/1/19 2:23 PM, Brian Bouterse wrote: > > I've finally gotten to read through the numbers and this thread. It is a > tradeoff but I am +1 for switching to UUIDs. I focus on the PostgreSQL UUID > vs int case because that is our default database. I don't think too much > about how things perform on MariaDB because they can improve their own > performance to catch up to PostgreSQL which regularly is performing better > afaict. I agree with the assessment of 30% ish slowdown in the large unit > cases for PostgreSQL. Still, I believe the advantages of switching to UUIDs > are worth it. Two main reasons stick out in my mind. > > 1. Our core code and all plugin code will always be compatible with common > db backends even when using bulk_create() > 2. We get database sharding with postgresql which you can only do with > UUID pks. I was advised this years ago by jcline. > > Performance and compatibility are a pretty classic trade-off. Overall I've > found that initial releases launch with less performance and improve (often > significantly) overtime. Consider the interpreter pypy (not pypi). It > started "roughly 2000x slower [at initial launch] than CPython, to roughly > 7x faster [now]" [0]. Launching Pulp 3.0 that is 30% slower in the > worst-case but runs everywhere with zero "db-behavior surprises" I think is > worth it. Also conversely, if we don't adopt UUIDs, how will we address > item 1 pre RC? > > @dawalker for the "can we have both" option, we probably can have some > db-specific codepaths, but I don't think doing an application wide PK type > change as a setting is feasible to support. The db specific codepaths are > one way performance improves over time. For the initial release, to keep > things simple I hope we don't have conditional database codepaths (for now). > > More discussion on this change is encouraged. Thanks @dalley so much for > all the detailed investigation! > > [0]: https://morepypy.blogspot.com/2018/09/the-first-15-years-of-pypy.html > > Thank you, > Brian > > On Fri, Mar 1, 2019 at 2:51 PM Dana Walker <[email protected]> wrote: > >> As I brought up on irc, I don't know how feasible the complications to >> maintenance would be going forward, but I would prefer if we could use some >> sort of settings in order to choose uuid or id based on MariaDB or >> PostgreSQL. I want us to work everywhere, but I'm really concerned at the >> impact to our users of a 30-40% efficiency drop in speed and storage. >> >> David wrote up a quick Proof of Concept after I brought this up but >> wasn't necessarily advocating it himself. I think Daniel and Dennis >> expressed some concerns. I'd like to see more people discussing it here >> with reasoning/examples on how doable something like this could be? >> >> If it's not on the table, I understand, but want to make sure we've >> considered all reasonable options, and that might not be a simple binary of >> either/or. >> >> Thanks, >> >> --Dana >> >> Dana Walker >> >> Associate Software Engineer >> >> Red Hat >> >> <https://www.redhat.com> >> <https://red.ht/sig> >> >> >> On Fri, Mar 1, 2019 at 9:15 AM David Davis <[email protected]> wrote: >> >>> I just want to bump this thread. If we hope to make the Pulp 3 RC date, >>> we need feedback today. >>> >>> David >>> >>> >>> On Wed, Feb 27, 2019 at 5:09 PM Matt Pusateri <[email protected]> >>> wrote: >>> >>>> Not sure if https://www.webyog.com/ Monyog will give a free opensource >>>> project license. But that might help diagnose the MariaDB performance. >>>> Monyog is really nice, I wish it supported Postgres. >>>> >>>> Matt P. >>>> >>>> On Tue, Feb 26, 2019 at 7:23 PM Daniel Alley <[email protected]> wrote: >>>> >>>>> Hello all, >>>>> >>>>> We've had an ongoing discussion about whether Pulp would be able to >>>>> perform acceptably if we switched back to UUID primary keys. I've >>>>> finished >>>>> doing the performance testing and I *think* the answer is yes. Although >>>>> to >>>>> be honest, I'm not sure that I understand why, in the case of MariaDB. >>>>> >>>>> I linked my testing methodology and results here: >>>>> https://pulp.plan.io/issues/4290#note-18 >>>>> >>>>> To summarize, I tested the following: >>>>> >>>>> * How long it takes to perform subsequent large (lazy) syncs, with >>>>> lots of content in the database (100-400k content units) >>>>> * How long it takes to perform various small but important database >>>>> queries >>>>> >>>>> The results were weirdly in contrast in some cases. >>>>> >>>>> The first four syncs (202,000 content total) behaved mostly the same >>>>> on PostgreSQL whether it used an autoincrement or UUID primary key. >>>>> Subsequent syncs had a performance drop of between 30-40%. Likewise, the >>>>> code snippets performed 30+% worse. Sync time scaled linearly"ish" with >>>>> the amont of content in the repository in both cases, which was a bit >>>>> surprising to me. The size of the database at the end was 30-40% larger >>>>> with UUID primary keys, 736 MB vs 521 MB. The gap would be smaller in >>>>> typical usage when you consider that most content types have more metadata >>>>> than FileContent (what I was testing). >>>>> >>>>> Autoincrement PostgreSQL (left) vs. UUID PostgreSQL (right) in diff >>>>> form >>>>> https://www.diffchecker.com/40AF8vvM >>>>> >>>>> With MariaDB the first sync was almost 80% slower than the first sync >>>>> w/ PostgreSQL, but every subsequent sync was as fast or faster, despite >>>>> the >>>>> tests of specific queries performing multiple times worse. Additionally >>>>> the sync performance did not decrease as rapidly as it did under >>>>> PostgreSQL. With MariaDB, one of my test queries that worked fine when >>>>> backed by PostgreSQL ended up hanging endlessly and I had to cut it off >>>>> after 25 or so minutes. [0] I would consider that a blocker to claiming >>>>> we >>>>> support MariaDB / MySQL. >>>>> >>>>> But overall I'm not sure how to interpret the fact that on one hand >>>>> the real-usage performance is equal or better better, and on the >>>>> performance of some of the underlying queries is noticably worse. Maybe >>>>> there's some weird caching going on in the backend, or the generated >>>>> indexes are different? >>>>> >>>>> UUID PostgreSQL (left) vs. UUID MariaDB (right) in diff form >>>>> https://www.diffchecker.com/W1nnIQgj >>>>> >>>>> I'd like to invite some discussion on this, but nothing I've mentioned >>>>> seems like it would be a problem for going forwards with using UUID >>>>> primary >>>>> keys in a general sense. If we're all in agreement about that engineering >>>>> decision then we can move forwards with that work. >>>>> >>>>> [0] for *some* but not all repository versions. No idea what's up >>>>> there. >>>>> >>>>> >>>>> >>>>> >>>>> >>>>> >>>>> >>>>> _______________________________________________ >>>>> Pulp-dev mailing list >>>>> [email protected] >>>>> https://www.redhat.com/mailman/listinfo/pulp-dev >>>>> >>>> _______________________________________________ >>>> Pulp-dev mailing list >>>> [email protected] >>>> https://www.redhat.com/mailman/listinfo/pulp-dev >>>> >>> _______________________________________________ >>> Pulp-dev mailing list >>> [email protected] >>> https://www.redhat.com/mailman/listinfo/pulp-dev >>> >> _______________________________________________ >> Pulp-dev mailing list >> [email protected] >> https://www.redhat.com/mailman/listinfo/pulp-dev >> > > _______________________________________________ > Pulp-dev mailing > [email protected]https://www.redhat.com/mailman/listinfo/pulp-dev > > > _______________________________________________ > Pulp-dev mailing list > [email protected] > https://www.redhat.com/mailman/listinfo/pulp-dev >
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