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HBase >> mail # user >> question about merge-join (or AND operator betwween colums)


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Re: question about merge-join (or AND operator betwween colums)
Ok. Understand.

But do you check is it really an issue? I think that it is only 1 IO here,
(especially
if compression used)? You have big rows?

2011/1/9 Jack Levin <[EMAIL PROTECTED]>

> Sorting is not the issue, the location of data can be in the beginning,
> middle or end, or any combination of thereof.  I only given the worst case
> scenario example, I understand that filtering will produce results we want
> but at cost of examining every row and offloading AND/join logic to the
> application.
>
> -Jack
>
> On Sat, Jan 8, 2011 at 1:59 PM, Andrey Stepachev <[EMAIL PROTECTED]> wrote:
>
> > More details on binary sorting you can read
> >
> >
> http://brunodumon.wordpress.com/2010/02/17/building-indexes-using-hbase-mapping-strings-numbers-and-dates-onto-bytes/
> >
> > 2011/1/8 Jack Levin <[EMAIL PROTECTED]>
> >
> > > Basic problem described:
> > >
> > > user uploads 1 image and creates some text -10 days ago, then creates
> > 1000
> > > text messages on between 9 days ago and today:
> > >
> > >
> > > row key          | fm:type --> value
> > >
> > >
> > > 00days:uid     | type:text --> text_id
> > >
> > > .
> > >
> > > .
> > >
> > > 09days:uid | type:text --> text_id
> > >
> > >
> > > 10days:uid     | type:photo --> URL
> > >
> > >          | type:text --> text_id
> > >
> > >
> > > Skip all the way to 10days:uid row, without reading 00days:id - 09:uid
> > > rows.
> > >  Ideally we do not want to read all 1000 entries that have _only_ text.
> >  We
> > > want to get to last entry in the most efficient way possible.
> > >
> > >
> > > -Jack
> > >
> > >
> > >
> > >
> > > On Sat, Jan 8, 2011 at 11:43 AM, Stack <[EMAIL PROTECTED]> wrote:
> > > > Strike that.  This is a Scan, so can't do blooms + filter.  Sorry.
> > > > Sounds like a coprocessor then.  You'd have your query 'lean' on the
> > > > column that you know has the lesser items and then per item, you'd do
> > > > a get inside the coprocessor against the column of many entries.  The
> > > > get would go via blooms.
> > > >
> > > > St.Ack
> > > >
> > > >
> > > > On Sat, Jan 8, 2011 at 11:39 AM, Stack <[EMAIL PROTECTED]> wrote:
> > > >> On Sat, Jan 8, 2011 at 11:35 AM, Jack Levin <[EMAIL PROTECTED]>
> > wrote:
> > > >>> Yes, we thought about using filters, the issue is, if one family
> > > >>> column has 1ml values, and second family column has 10 values at
> the
> > > >>> bottom, we would end up scanning and filtering 99990 records and
> > > >>> throwing them away, which seems inefficient.
> > > >>
> > > >> Blooms+filters?
> > > >> St.Ack
> > > >>
> > > >
> > >
> >
>