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From Amit Shah <amits...@gmail.com>
Subject Re: Disabling HBase Block Cache
Date Mon, 28 Mar 2016 07:36:18 GMT
Hi James,

Executing the alter table query in the format you specified indeed shows
the BLOCKCACHE => 'false' when describing the table on hbase shell.

Thanks,
Amit.

On Fri, Mar 25, 2016 at 10:57 PM, James Taylor <jamestaylor@apache.org>
wrote:

> Hi Amit,
>
> Have you see our documentation and examples for ALTER TABLE [1]?
>
> So you could do ALTER TABLE my_table SET BLOCKCACHE=false;
>
> If you want to prevent rows from being put in the block cache on a per
> query basis, you can use the /*+ NO_CACHE */ hint [2] on a query like this:
>
> SELECT /*+ NO_CACHE */ ...
>
> Thanks,
> James
>
> [1] https://phoenix.apache.org/language/index.html#alter
> [2] https://phoenix.apache.org/language/index.html#hint
>
> On Fri, Mar 25, 2016 at 6:39 AM, Amit Shah <amits.84@gmail.com> wrote:
>
>> I noticed that the charts <http://i.imgur.com/ZEJTHWt.png>on cloudera
>> indicate no block usage when the group by query is executed. This probably
>> means that the block cache is disabled. The only strange fact is that the
>> hbase shell describe command gave BLOCKCACHE => 'true'. It would be great
>> if someone could throw some light on this.
>>
>> P.S - Though disabling the block cache didn't speed up the group by query
>> but that seems like a separate topic of discussion.
>>
>> Thanks!
>>
>> On Fri, Mar 25, 2016 at 1:34 PM, Amit Shah <amits.84@gmail.com> wrote:
>>
>>> Hi,
>>>
>>> I am using apache hbase (version 1.0.0) and phoenix (version 4.6)
>>> deployed through cloudera. Since my aggregations with group by query is
>>> slow, I want to try out disabling the block cache for a particular hbase
>>> table. I tried a couple of approaches but couldn't succeed. I am verifying
>>> if the block cache is enabled/disabled through the hbase shell - describe
>>> 'my_table' command.
>>>
>>> 1. Set 'hfile.block.cache.size' property from cloudera console to 0
>>>
>>> 2. alter 'myTable', CONFIGURATION => {NAME => 'myColumnFamily',
>>> BLOCKCACHE => 'false'}
>>>
>>> Even after the above two steps, I get BLOCKCACHE => 'true' in the
>>> describe command output
>>>
>>> COLUMN FAMILIES DESCRIPTION {NAME => '0', DATA_BLOCK_ENCODING =>
>>> 'FAST_DIFF', BLOOMFILTER => 'ROW', REPLICATION_SCOPE => '0', COMPRESSION
=>
>>> 'NONE', VERSIONS => '1', MIN_VERSIONS => '0', TTL => 'FOREVER',
>>> KEEP_DELETED_CELLS => 'FALSE', BLOCKSIZE => '65536', IN_MEMORY => 'false',
>>> BLOCKCACHE => 'true'}
>>>
>>> What could be going wrong? Any suggestions?
>>>
>>> Thank you.
>>>
>>>
>>>
>>
>

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