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From Jean-Marc Spaggiari <jean-m...@spaggiari.org>
Subject Re: scan column families with different time ranges
Date Sun, 02 Aug 2015 13:22:02 GMT
Just thinking at loud :
"Cutting out the old store files could well also reduce disk IO for
that family by 100x."

What is "recent"  for your data? More than 7 days?  Or less? Don't you have
weekly major compactions?  If so and if you are scanning for  more than 7
days,  then you will read the older files anyway, no?

JM
Le 2015-08-02 05:57, "Ted Yu" <yuzhihong@gmail.com> a écrit :

> Dave:
> I wonder if Filter response can be enhanced in the following manner:
>
> http://pastebin.com/sb6apTPm
>
> My approach is based on using essential column family (column family A in
> your case) to guide whether the remaining column families should be loaded.
> To be specific, if outside the TimeRange you specify (last day), your
> filter returns ReturnCode.INCLUDE_AND_SEEK_NEXT_ROW.
>
> What do you think ?
>
> Cheers
>
> On Sat, Aug 1, 2015 at 8:06 PM, Dave Latham <latham@davelink.net> wrote:
>
> > Thanks for brainstorming, Ted.  That sounds like option 2 I listed using
> a
> > separate scanner for A vs B which "adds complexity to the job and gives
> up
> > the atomicity/consistency guarantees as new writes hit both column
> > families".
> >
> > On Sat, Aug 1, 2015 at 9:07 AM, Ted Yu <yuzhihong@gmail.com> wrote:
> >
> > > Can you achieve your goal with two scans ?
> > > The first scan specifies TimeRange corresponding to last day. This scan
> > > returns both column families.
> > > The other scan specifies TimeRange excluding last day. This scan
> returns
> > > column family A.
> > >
> > > Cheers
> > >
> > > On Sat, Aug 1, 2015 at 8:35 AM, Dave Latham <latham@davelink.net>
> wrote:
> > >
> > > > Hi Ted,
> > > >
> > > > Thanks for the suggestion, but I'm not sure that it helps my case
> much.
> > > I
> > > > wasn't very familiar with the feature, and it doesn't seem very well
> > > > documented - I had to go to the source and the originating JIRA to
> > > > understand how it works.  It sounds like it allows you to mark which
> > > column
> > > > families the filter operates on ("essential" seems an odd name).  If
> > any
> > > > data from those column families passes the filter, then the scan
> loads
> > > and
> > > > includes data from the remaining families without filtering it.  In
> my
> > > > case, it's not clear from a row's family A whether or not family B
> for
> > > that
> > > > row is required (though that could probably be added).  Moreover,
> even
> > > if a
> > > > row has recent data, we don't want to load all the old data from that
> > > row.
> > > > We'd prefer to be able to entirely skip reading the data off disk for
> > the
> > > > old store files.
> > > >
> > > > Dave
> > > >
> > > > On Sat, Aug 1, 2015 at 7:53 AM, Ted Yu <yuzhihong@gmail.com> wrote:
> > > >
> > > > > Have you considered using essential column family feature (through
> > > > Filter)
> > > > > ?
> > > > > In your case A would be the essential column family.
> > > > > Within TimeRange for recent data, the filter would return both
> column
> > > > > families.
> > > > > Outside the TimeRange, only family A is returned.
> > > > >
> > > > > Cheers
> > > > >
> > > > > On Sat, Aug 1, 2015 at 7:17 AM, Dave Latham <latham@davelink.net>
> > > wrote:
> > > > >
> > > > > > I have a table with 2 column families, call them A and B, with
> new
> > > data
> > > > > > regularly being added. They are very different sizes: B is 100x
> the
> > > > size
> > > > > of
> > > > > > A.  Among other uses for this data, I have a MapReduce job that
> > needs
> > > > to
> > > > > > read all of A, but only recent data from B (e.g. last day).
 Here
> > are
> > > > > some
> > > > > > methods I've considered:
> > > > > >
> > > > > >    1. Use a Filter to get throw out older data from B (this
is
> > what I
> > > > > >    currently do).  However, all the data from B still needs
to be
> > > read
> > > > > from
> > > > > >    disk, causing a disk IO bottleneck.
> > > > > >    2. Configure the table input format to read from B only,
> using a
> > > > > >    TimeRange for recent data, and have each map task open a
> > separate
> > > > > > scanner
> > > > > >    for A (without a TimeRange) then merge the data in the map
> task.
> > > > > > However,
> > > > > >    this adds complexity to the job and gives up the
> > > > atomicity/consistency
> > > > > >    guarantees as new writes hit both column families.
> > > > > >    3. Add a new column family C to the table with an additional
> > copy
> > > of
> > > > > the
> > > > > >    data in B, but set a TTL on it.  All writes duplicate the
data
> > > > written
> > > > > > to B
> > > > > >    and C.  Change the scan to include C instead of B.  However,
> > this
> > > > adds
> > > > > > all
> > > > > >    the overhead of another column family, more writes, and having
> > to
> > > > set
> > > > > > the
> > > > > >    TTL to the maximum of any time window I want to scan
> > efficiently.
> > > > > >    4. Implement an enhancement to HBase's Scan to allow giving
> each
> > > > > column
> > > > > >    family its own TimeRange.  The job would then be able to
skip
> > most
> > > > old
> > > > > >    large store files (hopefully all of them with tiered
> compaction
> > at
> > > > > some
> > > > > >    point).
> > > > > >
> > > > > > Does anyone have other suggestions?  Would HBase be willing
to
> > accept
> > > > > > updating Scan to have different TimeRange's for each column
> > families?
> > > > > >
> > > > > >
> > > > > > Dave
> > > > > >
> > > > >
> > > >
> > >
> >
>

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