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From André Hacker <andrephac...@gmail.com>
Subject Re: Difference between Hive and HCat table?
Date Sat, 09 Aug 2014 14:04:05 GMT
Thank you Andrew and Lefty, that helped a lot with clarification.

So the link tells me that, assuming a single metastore, everything done in
the HCat CLI will be reflected in Hive CLI and vice versa, but there are
some features exclusively available in Hive CLI and a few others
exclusively in HCat CLI (only table groups/permissions as far as I can see).

>From my user perspective it still looks a bit redundant to distinguish
these two CLIs. However, I understand that there are reasons to distinguish
HCat, which is a very generic metadata layer, and Hive, which is one (the
most popular one) of many engines running on HCat. The fact that HCat is
bundled with Hive and at the same time separated was always a bit confusing
to me, so I wanted to see if I missed something.

So thanks again, this section in the documentation was just what I was
looking for.

André
Am 05.08.2014 21:32 schrieb "Lefty Leverenz" <leftyleverenz@gmail.com>:

> Perhaps this documentation will help:  HCatalog CLI -- Hive CLI
> <https://cwiki.apache.org/confluence/display/Hive/HCatalog+CLI#HCatalogCLI-HiveCLI>
> .
>
> Also note the section that follows it, which begins "HCatalog supports all
> Hive Data Definition Language except those operations that require running
> a MapReduce job."
>
> -- Lefty
>
>
> On Tue, Aug 5, 2014 at 5:00 AM, Andrew Mains <andrew.mains@kontagent.com>
> wrote:
>
>> André,
>>
>> To my knowledge, your understanding is correct--given that both Hive and
>> HCatalog are pointing to the same metastore instance, all HCatalog table
>> operations should be
>> reflected in Hive, and vice versa. You should be able to use the Hive CLI
>> and hcat interchangeably to execute your DDL.
>>
>> Andrew
>>
>>
>> On 8/5/14, 12:23 AM, André Hacker wrote:
>>
>>> Hi,
>>>
>>> a very simple question: Is there a difference between a table in Hive
>>> and a table in HCat?
>>> In other words: Can I create a table in Hive that is invisible in HCat,
>>> or vice versa?
>>> (Assuming that Hive and HCat point to the same metastore)
>>>
>>> From my understanding, HCat is just a wrapper around the Hive metastore,
>>> so there should be no major difference. This is in line with my experience:
>>> If I create a table via the Hive CLI, it will be shown in HCat too when
>>> running hcat -e "show tables;". And vice versa.
>>>
>>> I ask because some online documentation makes me feel that I have to run
>>> my DDL in HCat to make it visible there. At least I didn't find documents
>>> that say that I can use either Hive CLI or HCat.
>>>
>>> Thanks,
>>>
>>> André Hacker
>>>
>>>
>>
>

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