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From Todd Lipcon <t...@cloudera.com>
Subject Re: CDH 5.5 - Kudu error not enough space remaining in buffer for op
Date Wed, 18 May 2016 13:25:18 GMT
Hi Abhi,

Will is right that the error is client-side, and probably happening because
your rows are so wide.Impala typically will batch 1000 rows at a time when
inserting into Kudu, so if each of your rows is 7-8KB, that will overflow
the max buffer size that Will mentioned. This seems quite probable if your
data is 1000 columns of doubles or int64s (which are 8 bytes each).

I don't think his suggested workaround will help, but you can try running
'set batch_size=500' before running the create table or insert query.

In terms of max supported columns, most of the workloads we are focusing on
are more like typical data-warehouse tables, on the order of a couple
hundred columns. Crossing into the 1000+ range enters "uncharted territory"
where it's much more likely you'll hit problems like this and quite
possibly others as well. Will be interested to hear your experiences,
though you should probably be prepared for some rough edges.

-Todd

On Tue, May 17, 2016 at 8:32 PM, William Berkeley <wdberkeley@cloudera.com>
wrote:

> Hi Abhi.
>
> I believe that error is actually coming from the client, not the server.
> See e,g,
> https://github.com/apache/incubator-kudu/blob/master/src/kudu/client/batcher.cc#L787
(NB
> that link is to master branch not the exact release you are using).
>
> If you look around there, you'll see that the max is set by something
> called max_buffer_size_, which appears to be hardcoded to 7 * 1024 * 1024
> bytes = 7MiB (and this is consistent with 6.96 + 0.0467 > 7).
>
> I think the simple workaround would be to do the CTAS as a CTAS + insert
> as select. Pick a condition that bipartitions the table, so you don't get
> errors trying to double insert rows.
>
> -Will
>
> On Tue, May 17, 2016 at 4:45 PM, Abhi Basu <9000revs@gmail.com> wrote:
>
>> What is the limit of columns in Kudu?
>>
>> I am using 1000 gen dataset, specifically the chr22 table which has
>> 500,000 rows x 1101 columns. This table has been built In Impala/HDFS. I am
>> trying to create a new Kudu table as select from that table. I get the
>> following error:
>>
>> Error while applying Kudu session.: Incomplete: not enough space
>> remaining in buffer for op (required 46.7K, 6.96M already used
>>
>> When looking at http://pcsd-cdh2.local.com:8051/mem-trackers, I see the
>> following. What configuration needs to be tweaked?
>>
>>
>> Memory usage by subsystem
>> IdParentLimitCurrent ConsumptionPeak consumption
>> root none 50.12G 4.97M 6.08M
>> block_cache-sharded_lru_cache root none 937.9K 937.9K
>> code_cache-sharded_lru_cache root none 1B 1B
>> server root none 2.3K 201.4K
>> tablet-00000000000000000000000000000000 server none 530B 200.1K
>> MemRowSet-6 tablet-00000000000000000000000000000000 none 265B 265B
>> txn_tracker tablet-00000000000000000000000000000000 64.00M 0B 28.5K
>> DeltaMemStores tablet-00000000000000000000000000000000 none 265B 87.8K
>> log_block_manager server none 1.8K 2.7K
>>
>> Thanks,
>> --
>> Abhi Basu
>>
>
>


-- 
Todd Lipcon
Software Engineer, Cloudera

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