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From Amitanand Aiyer <amitanan...@fb.com>
Subject Re: Slow row deletion performance in comparison to insertion
Date Wed, 27 Jun 2012 22:05:40 GMT
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" <jeffw@qualtrics.com> 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
> 

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