-Re: Using HBase for Deduping
Michael Segel 2013-02-15, 01:33
What constitutes a duplicate?
An over simplification is to do a HTable.checkAndPut() where you do the put if the column doesn't exist.
Then if the row is inserted (TRUE) return value, you push the event.
That will do what you want.
At least at first blush.
On Feb 14, 2013, at 3:24 PM, Viral Bajaria <[EMAIL PROTECTED]> wrote:
> Given the size of the data (> 1B rows) and the frequency of job run (once
> per hour), I don't think your most optimal solution is to lookup HBase for
> every single event. You will benefit more by loading the HBase table
> directly in your MR job.
> In 1B rows, what's the cardinality ? Is it 100M UUID's ? 99% unique UUID's ?
> Also once you have done the unique, are you going to use the data again in
> some other way i.e. online serving of traffic or some other analysis ? Or
> this is just to compute some unique #'s ?
> It will be more helpful if you describe your final use case of the computed
> data too. Given the amount of back and forth, we can take it off list too
> and summarize the conversation for the list.
> On Thu, Feb 14, 2013 at 1:07 PM, Rahul Ravindran <[EMAIL PROTECTED]> wrote:
>> We can't rely on the the assumption event dupes will not dupe outside an
>> hour boundary. So, your take is that, doing a lookup per event within the
>> MR job is going to be bad?
>> From: Viral Bajaria <[EMAIL PROTECTED]>
>> To: Rahul Ravindran <[EMAIL PROTECTED]>
>> Cc: "[EMAIL PROTECTED]" <[EMAIL PROTECTED]>
>> Sent: Thursday, February 14, 2013 12:48 PM
>> Subject: Re: Using HBase for Deduping
>> You could do with a 2-pronged approach here i.e. some MR and some HBase
>> lookups. I don't think this is the best solution either given the # of
>> events you will get.
>> FWIW, the solution below again relies on the assumption that if a event is
>> duped in the same hour it won't have a dupe outside of that hour boundary.
>> If it can have then you are better of with running a MR job with the
>> current hour + another 3 hours of data or an MR job with the current hour +
>> the HBase table as input to the job too (i.e. no HBase lookups, just read
>> the HFile directly) ?
>> - Run a MR job which de-dupes events for the current hour i.e. only runs on
>> 1 hour worth of data.
>> - Mark records which you were not able to de-dupe in the current run
>> - For the records that you were not able to de-dupe, check against HBase
>> whether you saw that event in the past. If you did, you can drop the
>> current event or update the event to the new value (based on your business
>> - Save all the de-duped events (via HBase bulk upload)
>> Sorry if I just rambled along, but without knowing the whole problem it's
>> very tough to come up with a probable solution. So correct my assumptions
>> and we could drill down more.
>> On Thu, Feb 14, 2013 at 12:29 PM, Rahul Ravindran <[EMAIL PROTECTED]>
>>> Most will be in the same hour. Some will be across 3-6 hours.
>>> Sent from my phone.Excuse the terseness.
>>> On Feb 14, 2013, at 12:19 PM, Viral Bajaria <[EMAIL PROTECTED]>
>>>> Are all these dupe events expected to be within the same hour or they
>>>> can happen over multiple hours ?
>>>> From: Rahul Ravindran
>>>> Sent: 2/14/2013 11:41 AM
>>>> To: [EMAIL PROTECTED]
>>>> Subject: Using HBase for Deduping
>>>> We have events which are delivered into our HDFS cluster which may
>>>> be duplicated. Each event has a UUID and we were hoping to leverage
>>>> HBase to dedupe them. We run a MapReduce job which would perform a
>>>> lookup for each UUID on HBase and then emit the event only if the UUID
>>>> was absent and would also insert into the HBase table(This is
>>>> simplistic, I am missing out details to make this more resilient to
>>>> failures). My concern is that doing a Read+Write for every event in MR
>>>> would be slow (We expect around 1 Billion events every hour). Does
Michael Segel | (m) 312.755.9623
Segel and Associates