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From Eugene Koifman <>
Subject Re: Locking when using the Metastore/HCatalog APIs.
Date Tue, 27 Oct 2015 22:43:27 GMT
Wouldn't it make more sense for the api to acquire required locks automatically?   That seems
like a simpler user model.

From: Alan Gates <<>>
Reply-To: "<>" <<>>
Date: Tuesday, October 27, 2015 at 11:34 AM
To: "<>" <<>>
Subject: Re: Locking when using the Metastore/HCatalog APIs.

Answers inlined.

Elliot West<>
October 22, 2015 at 6:40
I notice from the Hive locking wiki page<>
that locks may be acquired for a range of HQL DDL operations. I wanted to know how the locking
scheme mapped mapped/employed by equivalent operations in the Metastore and HCatalog APIs.
Consider the operation:

alter table T1 drop partition P1

This apparently requires a shared lock on T1 and an exclusive lock on P1. However, when following
the invocation chain on the equivalent APIs I can see no acquisition of such locks:


I notice that IMetaStoreClient exposes methods to lock and unlock resources and I have used
these when working with the ACID APIs. However I can find nothing similar on the HCatalog
API. As a user of these APIs:

  1.  Do I need to acquire/release locks as declared on the wiki page when using equivalent
operations in these APIs?


  1.  If not, why not?
  2.  Ideally, should the HCatClient also expose lock/unlock methods like the Metastore API?


  1.  If not, why not?

Thank you - Elliot.

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