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From Ted Yu <yuzhih...@gmail.com>
Subject Re: 1 table, 1 dense CF => N tables, 1 dense CF ?
Date Sat, 10 Jan 2015 00:11:55 GMT
Thanks for the confirmation, Gary.

The change has been done through HBASE-12834.

Cheers

On Fri, Jan 9, 2015 at 1:01 PM, Gary Helmling <ghelmling@gmail.com> wrote:

> ScanType is a parameter of RegionObserver preCompact() and
> preCompactScannerOpen().  It seems like anything we are explicitly
> providing to coprocessor hooks should be LimitedPrivate.
>
> On Fri, Jan 9, 2015 at 12:26 PM, Ted Yu <yuzhihong@gmail.com> wrote:
>
> > w.r.t. ScanType, here is the logic used by DefaultCompactor:
> >
> >         ScanType scanType =
> >
> >             request.isAllFiles() ? ScanType.COMPACT_DROP_DELETES :
> > ScanType.
> > COMPACT_RETAIN_DELETES;
> >
> > BTW ScanType is currently marked InterfaceAudience.Private
> >
> > Should it be marked LimitedPrivate ?
> >
> > Cheers
> >
> > On Fri, Jan 9, 2015 at 12:19 PM, Gary Helmling <ghelmling@gmail.com>
> > wrote:
> >
> > > >
> > > >
> > > > 2) is more expensive than 1).
> > > > I'm wondering if we could use Compaction Coprocessor for 2)?
> HBaseHUT
> > > > needs to be able to grab N rows and merge them into 1, delete those N
> > > rows,
> > > > and just write that 1 new row.  This N could be several thousand
> rows.
> > > > Could Compaction Coprocessor really be used for that?
> > > >
> > > >
> > > It would depend on the details.  If you're simply aggregating the data
> > into
> > > one row, and:
> > > * the thousands of rows are contiguous in the scan
> > > * you can somehow incrementally update or emit the new row that you
> want
> > to
> > > create so that you don't need to retain all the old rows in memory
> > > * the new row you want to emit would sort sequentially into the same
> > > position
> > >
> > > Then overriding the scanner used for compaction could be a good
> solution.
> > > This would allow you to transform the cells emitted during compaction,
> > > including dropping the cells from the old rows and emitting new
> > > (transformed) cells for the new row.
> > >
> > >
> > > > Also, would that come into play during minor or major compactions or
> > > both?
> > > >
> > > >
> > > You can distinguish between them in your coprocessor hooks based on
> > > ScanType.  So up to you.
> > >
> >
>

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