First, remember that the Calcite "interface Schema" is quite low level. It is basically a namespace that contains a set of tables and a set of sub-schemas. You can, and probably should, make it immutable.
A Schema instance doesn’t know its own name or path. That allows you to “mount” it (as you would mount a filesystem) under several paths. This gives you a clue for how you could serve multiple tenants, each possibly seeing the same schema and tables (or possibly seeing different subsets). Just set a different root schema for each tenant’s connection. I believe that’s analogous to how a container like Docker works. Calcite does not, by default, write anything to disk. The built-in adapters read from foreign wrappers (e.g. connecting to another JDBC database or Cassandra or MongoDB or CSV files) but then process data in memory. If you wanted to, you could write a merge sort algorithm that uses sort runs on disk. But that’s not in Calcite currently. Julian > On Oct 19, 2022, at 8:19 PM, JiaTao Tao <[email protected]> wrote: > > In fact, you can change calcite to use like HMS to manager schema > > Regards! > > Aron Tao > > > Mike Albritton <[email protected]> 于2022年10月20日周四 07:16写道： > >> Hi all, >> >> >> I am considering using Calcite in a multi-tenant application that can run >> queries from different customers in the same process and have a few >> questions for those familiar with the code about this approach. >> >> >> Specifically, I would like to know if metadata is completely separated >> per-schema that is loaded or if it is ever shared between schemas? Also, I >> read in the docs somewhere that Calcite manages memory for cross schema >> joins which seemed to suggest it may persist data to disk temporarily. Is >> this the case or is there somewhere I can learn more about how data >> persistence works? Are there any other concerns that I should have when >> running Calcite in a multi-tenant application? >> >> >> Finally, if you or someone you know may be interested in a short term >> contract to assist with a Calcite POC, let me know. >> >> >> Regards, >> >> Mike >>
