Thanks Jan! To avoid spreading discussions on multiple places, I will continue the comments on the doc. Also it is easier to run into communication gaps in email threads since effectively we have one thread, but in docs we have many.
Thanks, Walaa. On Tue, Mar 26, 2024 at 6:27 AM Jan Kaul <jank...@mailbox.org.invalid> wrote: > I've added a description to the "Combined metadata" Option of Walaa's > document. I'm also adding it here: > > This option treats the underlying view and storage table as a combined > catalog object. The operation of this combined approach can be best > demonstrated by looking at the different layers of the Iceberg > implementation. In the top layer is the Iceberg *library* that interacts > with a particular Iceberg *catalog*. The catalog handles the access to > the metadata *storage*. > This option uses a combined storage object to store view and table > metadata related to the materialized view. To avoid the definition of an > entirely new metadata format, the storage object is composed of the view > and table metadata. Additionally the combined storage object has a *single > identifier* in the catalogs. The Iceberg library treats the materialized > view as a separate view and a storage table object, it is only at the > catalog and storage layer that the materialized view is treated as a single > entity. > To reuse most of the existing TableCatalog, ViewCatalog and their > operations, the table and view catalog can be thought of as “filters” ( > lenses <https://medium.com/javascript-scene/lenses-b85976cb0534>), that > allow the interaction only with the corresponding part of the MV storage > object. Performing a “CommitView” operation on the view catalog will only > affect the view metadata part of the combined MV storage object. And > similarly, performing a “CommitTable” operation on the table catalog will > only affect the table metadata part of the combined MV storage object. Both > catalogs use the same identifier for operations on the materialized view. > The creation of a materialized view is done with the “createView” > operation (with additional materialization flag) on the view catalog, > creating a combined MV storage object with an empty storage table. > One could entirely reuse the existing API for loading the materialized > view metadata as follows. When calling the “loadView” method of the > ViewCatalog, the catalog implementation fetches and caches the entire MV > metadata object in process and returns the view metadata part. When the > “loadTable” method of the TableCatalog is then called to obtain the storage > table, it returns the table part of the cached MV metadata object. > > Best wishes, > > Jan > On 3/26/24 9:08 AM, Jan Kaul wrote: > > I think it makes sense if I use the "Description" section of your document > to clarify how I imagine a combined MV solution to look like. This would > simplify the discussion about pros and cons, because we can reference or > extend the description. I will try to find the time later today. > > Thanks, > > Jan > On 3/25/24 4:39 PM, Walaa Eldin Moustafa wrote: > > Thanks Jan! I am not sure if you would like to make suggestions to revise > the options themselves or the current options pros and cons. In either > case, as mentioned earlier, we can do that on the doc and once we agree on > the options and their pros and cons we can move forward. How does that > sound? > > Thanks, > Walaa. > > > On Mon, Mar 25, 2024 at 7:45 AM Jan Kaul <jank...@mailbox.org.invalid> > <jank...@mailbox.org.invalid> wrote: > >> I have the feeling that the current pros and cons from the summary target >> a version of the MV spec that wasn't really part of the discussion. The >> current arguments target a completely new specification for materialized >> views which we agreed on, is out of scope. Instead of a completely new >> specification the argument was made for a MV metadata object that embeds >> the View and the Table metadata, which was Option 6 >> <https://docs.google.com/spreadsheets/d/1a0tlyh8f2ft2SepE7H3bgoY2A0q5IILgzAsJMnwjTBs/edit#gid=0&range=G3> >> in Jack's summary document. With that approach the "commitView" and >> "commitTable" operations don't have to be changed and only the "loadView" >> operation has to be adopted. Additionally, compaction and snapshot >> expiration can be reused for the embedded solution. With that in mind, the >> cons 2, 4, 5, 6 from the summary don't really apply. >> Furthermore, I think we should distinguish between pros and cons for the >> implementers and the users. Because most of the pros (no new operations) >> for separate objects (option1) are for the implementers and most of the >> pros (single logical object, doesn't require 2 loads) for combined objects >> (option3) are for the users. In my opinion, in the long run the design >> decisions should be focused more on the user preferences than the >> implementers. >> On 3/25/24 14:49, Benny Chow wrote: >> >> Hi Manu >> >> This is Walaa's Spark implementation for option 1: >> https://github.com/apache/iceberg/pull/9830/files/a9e1bee3b5bf5914e5330d3b195042aea33868c9 >> There's no code for option 2 yet. >> >> Best >> Benny >> >> On Mon, Mar 25, 2024 at 12:37 AM Manu Zhang <owenzhang1...@gmail.com> >> wrote: >> >>> Thanks Walaa for the summary. It's unclear to me which are the reference >>> implementation for option 1 and reference MV spec for option 2 from the >>> context. I can find some links in the References section but not sure which >>> should be referred to respectively. >>> >>> On Mon, Mar 25, 2024 at 3:38 AM Walaa Eldin Moustafa < >>> wa.moust...@gmail.com> wrote: >>> >>>> Thanks Himadri for the questions. At this point, our objective is to >>>> have a common understanding of both options and their pros and cons. The >>>> best way to achieve this is to iterate on the doc to discuss the details of >>>> each option or their pros and cons. We can always add more details or >>>> update the pros and cons. The main thing is to keep the options to two so >>>> that we keep the scope manageable. >>>> >>>> Once we have a common understanding, it will be easy to make a choice >>>> and move forward. Therefore, I would suggest reframing your questions as >>>> either adding suggestions to add more details to the options, questions on >>>> how either works, or discussions of their pros and cons on the doc. >>>> >>>> Thanks, >>>> Walaa. >>>> >>>>
