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RE: HBase Put
Pamecha, Abhishek 2012-08-22, 21:41
Thanks. I should have read there first. :)

Thanks,
Abhishek
-----Original Message-----
From: Jason Frantz [mailto:[EMAIL PROTECTED]]
Sent: Wednesday, August 22, 2012 2:05 PM
To: [EMAIL PROTECTED]
Subject: Re: HBase Put

Abhishek,

Setting your column family's bloom filter to ROWCOL will include qualifiers:

http://hbase.apache.org/book.html#schema.bloom

-Jason

On Wed, Aug 22, 2012 at 1:49 PM, Pamecha, Abhishek <[EMAIL PROTECTED]> wrote:

> Can I enable bloom filters per block at column qualifier levels too?
> That way, will small block sizes, I can selectively load only few data
> blocks in memory. Then I can do some trade off between block size and
> bloom filter false positive rate.
>
> I am designing for a wide table scenario with thousands and millions
> of columns and thus I don't really want to stress on checks for blocks
> having more than one row key.
>
> Thanks,
> Abhishek
>
>
> -----Original Message-----
> From: Mohit Anchlia [mailto:[EMAIL PROTECTED]]
> Sent: Wednesday, August 22, 2012 11:09 AM
> To: [EMAIL PROTECTED]
> Subject: Re: HBase Put
>
> On Wed, Aug 22, 2012 at 10:20 AM, Pamecha, Abhishek <[EMAIL PROTECTED]>
> wrote:
>
> > So then a GET query means one needs to look in every HFile where key
> > falls within the min/max range of the file.
> >
> > From another parallel thread, I gather, HFile comprise of blocks
> > which, I think, is an atomic unit of persisted data in HDFS.(please
> correct if not).
> >
> > And that each block for a HFile has a range of keys. My key can
> > satisfy the range for the block and yet may not be present. So, all
> > the blocks that match the range for my key, will need to be scanned.
> > There is one block index per HFile which sorts blocks by key ranges.
> > This index help in reducing the number of blocks to scan by
> > extracting only those blocks whose ranges satisfy the key.
> >
> > In this case, if puts are random wrt order, each block may have
> > similar range and it may turn out that Hbase needs to scan every
> > block for the File. This may not be good for performance.
> >
> > I just want to validate my understanding.
> >
> >
> If you have such a use case I think best practice is to use bloom filters.
> I think in generaly it's a good idea to atleast enable bloom filter at
> row level.
>
> > Thanks,
> > Abhishek
> >
> >
> > -----Original Message-----
> > From: lars hofhansl [mailto:[EMAIL PROTECTED]]
> >  Sent: Tuesday, August 21, 2012 5:55 PM
> > To: [EMAIL PROTECTED]
> > Subject: Re: HBase Put
> >
> > That is correct.
> >
> >
> >
> > ________________________________
> >  From: "Pamecha, Abhishek" <[EMAIL PROTECTED]>
> > To: "[EMAIL PROTECTED]" <[EMAIL PROTECTED]>; lars hofhansl <
> > [EMAIL PROTECTED]>
> > Sent: Tuesday, August 21, 2012 4:45 PM
> > Subject: RE: HBase Put
> >
> > Hi Lars,
> >
> > Thanks for the explanation. I still have a little doubt:
> >
> > Based on your description, given gets do a merge sort, the data on
> > disk is not kept sorted across files, but just sorted within a file.
> >
> > So, basically if on two separate days, say these keys get inserted:
> >
> > Day1: File1:   A B J M
> > Day2: File2:  C D K P
> >
> > Then each file is sorted within itself, but scanning both files will
> > require Hbase to use merge sort to produce a sorted result. Right?
> >
> > Also, File 1 and File2 are immutable, and during compactions, File 1
> > and
> > File2 are compacted and sorted using merge sort to a bigger File3.
> > Is that correct too?
> >
> > Thanks,
> > Abhishek
> >
> >
> > -----Original Message-----
> > From: lars hofhansl [mailto:[EMAIL PROTECTED]]
> > Sent: Tuesday, August 21, 2012 4:07 PM
> > To: [EMAIL PROTECTED]
> > Subject: Re: HBase Put
> >
> > In a nutshell:
> > - Puts are collected in memory (in a sorted data structure)
> > - When the collected data reaches a certain size it is flushed to a
> > new file (which is sorted)
> > - Gets do a merge sort between the various files that have been