Hi Fokko I like the idea, but I think it's more a workaround and could be confusing for users :)
Regards JB On Tue, Nov 12, 2024 at 2:53 PM Fokko Driesprong <fo...@apache.org> wrote: > > Hey Gabor, > > Thanks for raising this. While reading this, my first thought is to leverage > the `tableExists` operation: > https://github.com/apache/iceberg/blob/e3f39972863f891481ad9f5a559ffef093976bd7/open-api/rest-catalog-open-api.yaml#L1129-L1160 > > This doesn't return anything today, but we could return a payload to the > latest metadata.json. > > Looking forward to what others think. > > Kind regards, > Fokko > > > > > Op di 12 nov 2024 om 14:33 schreef Shani Elharrar > <sh...@upsolver.com.invalid>: >> >> I recommend option (b), provided there is no partial metadata loading. We >> implemented option (b) internally to facilitate partial metadata loading, as >> we have tables with hundreds of thousands of snapshots. This results in >> metadata that occupies approximately 500 MB in memory (excluding the >> JsonNodes), which is a significant load for some of our services. >> >> Shani. >> >> On 12 Nov 2024, at 14:12, Gabor Kaszab <gaborkas...@apache.org> wrote: >> >> Hey Iceberg Community, >> >> Background: >> Impala is designed in a way to cache the Iceberg table metadata (BaseTable >> objects in practice) for faster access. Currently, Impala is tightly coupled >> with HMS and in turn with the HiveCatalog, and in order to keep the cached >> table objects up-to-date there is a notification mechanism driven by HMS to >> notify Impala about any changes in the table metadata. >> The Impala community is actively looking for ways to decouple HMS from >> Impala and provide a way to use Impala without the need for HMS, and get the >> Iceberg table metadata from other catalog Implementations mainly focusing >> now on REST catalogs. >> >> Problem to solve: >> We identified a particular missing functionality in the current REST spec: >> For engines that cache table metadata currently there is no way to check if >> that table metadata is up-to-date or not, and whether the engine should >> reload the metadata for that table or not without getting a whole table >> object from the catalog. For this I think the REST catalog (but in fact I >> think this could apply to any other catalogs) should be able to answer a >> question like: >> "Hi Catalog, I have this version of this table, is it up-to-date?" >> >> Proposal: >> I've been following the discussion about partial metadata loading that could >> be also used to answer the above question, but I have the impression now >> that the conversation stopped making any progress. >> So instead of waiting for partial metadata loading I propose to have an >> addition to the REST spec now to answer the question I raised above: >> >> a) boolean isLatest(TableIdentifier ident, String metadataLocation); >> b) String metadataLocation(TableIdentifier ident); >> >> Any of the above 2 approaches could help engines to decide if they have to >> invalidate/reload particular table metadata in the cache. I personally would >> go for option a) but would be open to hear other opinions. >> >> I'd like to know if the community could support me extending the REST spec >> with any of the 2 options. >> >> Regards, >> Gabor >> >>
