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 > <https://lists.apache.org/thread/ll3q30410gfrr89lynojj7b2kyh1xgh9> 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 > > >
