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https://issues.apache.org/jira/browse/HIVE-18685?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16362969#comment-16362969
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Alan Gates commented on HIVE-18685:
-----------------------------------
Finally, the comments on the Thrift changes:
I am in full agreement that we need to make a v2 of the API. I would like to
start that discussion with asking if we should stick with Thrift or move to
something else. But, I don't want to tie this (or any other) feature to that,
as that will be a many month project with a complex migration plan.
I also want this to be 100% backwards compatible, meaning old clients with no
knowledge of catalogs should still be able to work. So I don't want to change
existing calls like get_table() to add the catalog name.
Alexander's idea of re-using the existing Thrift calls by jamming the catalog
name into the dbname is very interesting. It avoid duplicating 75% of the
existing Thrift calls. I would only need to add Thrift calls for
createCatalog, getCatalog, etc. I'll explore this and see if it's viable. I
think I will likely still change HiveMetaStoreClient to add methods with
explicit catalog name, but that is much easier than adding thrift methods. And
in HiveMetaStoreClient I can explicitly deprecate the old methods, giving users
a warning not to continue using them. This will also hide 95% of our users
from the hackery.
> Add catalogs to metastore
> -------------------------
>
> Key: HIVE-18685
> URL: https://issues.apache.org/jira/browse/HIVE-18685
> Project: Hive
> Issue Type: New Feature
> Components: Metastore
> Affects Versions: 3.0.0
> Reporter: Alan Gates
> Assignee: Alan Gates
> Priority: Major
> Attachments: HMS Catalog Design Doc.pdf
>
>
> SQL supports two levels of namespaces, called in the spec catalogs and
> schemas (with schema being equivalent to Hive's database). I propose to add
> the upper level of catalog. The attached design doc covers the use cases,
> requirements, and brief discussion of how it will be implemented in a
> backwards compatible way.
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