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From Venkatesh <vramanatha...@aol.com>
Subject Re: How to delete rows in a FIFO manner
Date Fri, 06 Aug 2010 15:59:35 GMT

 I wrestled with that idea of time bounded tables..Would it make it harder to write code/run
map reduce
on multiple tables ? Also, how do u decide to when to do the cut over (start of a new day,
& if u do how to process data that cross those time boundaries efficiently..
Guess that is not your requirement..

If it is fixed time cut over, is n't enough to set the TTL timestamp ? 

 Interesting thread..thanks



-----Original Message-----
From: Thomas Downing <tdowning@proteus-technologies.com>
To: user@hbase.apache.org <user@hbase.apache.org>
Sent: Fri, Aug 6, 2010 11:39 am
Subject: Re: How to delete rows in a FIFO manner

Thanks for the suggestions.  The problem isn't generating the 
Delete objects, or the delete operation itself - both are fast 
enough.  The problem is generating the list of row keys from 
which the Delete objects are created. 
For now, the obvious work-around is to create and drop 
tables on the fly, using HBaseAdmin, with the tables being 
time-bounded. When the high end of a table passes the expiry 
time, just drop the table. When a table is written with the first 
record greater than the low bound, create a new table for the 
next time interval. 
As I am having other problems related to high ingest rates, 
the fact may be that I am just using the wrong tool for the job. 
On 8/6/2010 10:24 AM, Jean-Daniel Cryans wrote: 
> If the inserts are coming from more than 1 client, and your are trying 
> to delete from only 1 client, then likely it won't work. You could try 
> using a pool of deleters (multiple threads that delete rows) that you 
> feed from the scanner. Or you could run a MapReduce that would 
> parallelize that for you, that takes your table as an input and that 
> outputs Delete objects. 
> J-D 
> On Fri, Aug 6, 2010 at 5:50 AM, Thomas Downing 
> <tdowning@proteus-technologies.com>  wrote: 
>    >> Hi, 
>> Continuing with testing HBase suitability in a high ingest rate 
>> environment, I've come up with a new stumbling block, likely 
>> due to my inexperience with HBase. 
>> We want to keep and purge records on a time basis: i.e, when 
>> a record is older than say, 24 hours, we want to purge it from 
>> the database. 
>> The problem that I am encountering is the only way I've found 
>> to delete records using an arbitrary but strongly ordered over 
>> time row id is to scan for rows from lower bound to upper 
>> bound, then build an array of Delete using 
>> for Result in ResultScanner 
>>     add new Delete( Result.getRow( ) ) to Delete array. 
>> This method is far too slow to keep up with our ingest rate; the 
>> iteration over the Results in the ResultScanner is the bottleneck, 
>> even though the Scan is limited to a single small column in the 
>> column family. 
>> The obvious but naive solution is to use a sequential row id 
>> where the lower and upper bound can be known.  This would 
>> allow the building of the array of Delete objects without a scan 
>> step.  Problem with this approach is how do you guarantee a 
>> sequential and non-colliding row id across more than one Put'ing 
>> process, and do it efficiently.  As it happens, I can do this, but 
>> given the details of my operational requirements, it's not a simple 
>> thing to do. 
>> So I was hoping that I had just missed something.  The ideal 
>> would be a Delete object that would take row id bounds in the 
>> same way that Scan does, allowing the work to be done all 
>> on the server side.  Does this exists somewhere?  Or is there 
>> some other way to skin this cat? 
>> Thanks 
>> Thomas Downing 
>>      > -- 
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