Grokbase Groups HBase user June 2012
FAQ
Looking at HBASE-6284 it seems that deletes are not batched at the regionserver level so that is the
reason for the performance degradation. Additionally HBASE-5941 with the locks is also contributing
to the performance degradation.

So until those changes get into an hbase release I just have to live with the slower performance.
Is there anything I need to do on my end?

Just as a sanity check, I tried setting a timestamp in the delete object but it made no difference.
I'll batch my deletes at end as you suggested (as memory allows).

Thanks,
~Jeff
On 6/27/2012 4:11 PM, Ted Yu wrote:
Amit:
Can you point us to the JIRA or changelist in 0.89-fb ?

Thanks
On Wed, Jun 27, 2012 at 3:05 PM, Amitanand Aiyer wrote:

There was some difference in the way locks are taken for batched deletes
and puts. This was fixed for 89.

I wonder if the same could be the issue here.

Sent from my iPhone
On Jun 27, 2012, at 2:04 PM, "Jeff Whiting" wrote:

I'm struggling to understand why my deletes are taking longer than my
inserts. My understanding is that a delete is just an insertion of a
tombstone. And I'm deleting the entire row.
I do a simple loop (pseudo code) and insert the 100 byte rows:

for (int i=0; i < 50000; i++)
{
puts.append(new Put(rowkey[i], oneHundredBytes[i]));

if (puts.size() % 1000 == 0)
{
Benchmark.start();
table.batch(puts);
Benchmark.stop();
}
}


The above takes about 8282ms total.

However the delete takes more than twice as long:

Iterator it = table.getScannerScan(rowkey[0],
rowkey[50000-1]).iterator();
while(it.hasNext())
{
r = it.next();
deletes.append(new Delete(r.getRow()));
if (deletes.size() % 1000 == 0)
{
Benchmark.start();
table.batch(deletes);
Benchmark.stop();
}
}

The above takes 17369ms total.

I'm only benchmarking the deletion time and not the scan time.
Additionally if I batch the deletes into one big one at the end (rather
than while I'm scanning) it takes about the same amount of time. I am
deleting the entire row so I wouldn't think it would be doing a read before
the delete (
http://mail-archives.apache.org/mod_mbox/hbase-user/201206.mbox/%3CE83D30E8F408F94A96F992785FC29D82063395D6@s2k3mntaexc1.mentacapital.local%3E
).
Any thoughts on why it is slower and how I can speed it up?

Thanks,
~Jeff

--
Jeff Whiting
Qualtrics Senior Software Engineer
jeffw@qualtrics.com
--
Jeff Whiting
Qualtrics Senior Software Engineer
jeffw@qualtrics.com

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categorieshbase, hadoop
postedJun 27, '12 at 9:04p
activeJun 28, '12 at 2:38p
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websitehbase.apache.org

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