Re: How to define a custom filter to skip some amount of rows?

[NNever]

Thanks dmitriy, I will try the hint

2012/2/18 Dmitriy Lyubimov <dlie...@gmail.com>

> Filters support re-seek functionality. Hint can be given on the point
> of re-seek. Re-seek can be applied to either columns or rows
> (basically, hint is the new target of re-seek as key-value). You can
> find details in the hbase book (and perhaps somewhere online, too).
>
> -d
>
> On Mon, Feb 13, 2012 at 5:27 PM, NNever <nnever...@gmail.com> wrote:
> > Hello~
> > In HBase-0.92.0rc4.
> > If I need to skip some amount of rows from the scan result, how can I
> > define a custom filter to do it?
> > Here is my solution:
> >
> > *public class SkipFilter extends FilterBase{*
> > *    private long totalSkip = -1;*
> > *    private long currentSkip = 0;*
> > *    *
> > *    public SkipFilter(){}*
> > *
> > *
> > *    public SkipFilter(long totalSkip){*
> > *        this.totalSkip = totalSkip;*
> > *        currentSkip = 0;*
> > *    }*
> > *
> > *
> > *    // Only override this method*
> > *    public boolean filterRowKey(byte[] buffer, int offset, int length){*
> > *        if(currentSkip < totalSkip){*
> > *                currentSkip++;*
> > *                return true;*
> > *        }else{*
> > *                return false;*
> > *        }*
> > *    }*
> > *
> > *
> > *    ...readFileds...*
> > *    ...write...*
> > *}*
> >
> > And used like this:
> >
> > *Scan scan = new Scan();*
> > *scan.setStartRow(xxx);*
> > *scan.setEndRow(xxx);*
> > *Filter someFilter = new XXXFilter();*
> > *Filter skipFilter = new SkipFilter(100);*
> > *scan.setFilter(new FilterList(someFilter,...,skipFilter));*
> > *...doScan....*
> >
> > *
> > *
> > Well, it works fine.  I scan some table, and the result can jump the
> first
> > 100 rows, start from the 101th suitable row.
> > But when I delete some row from this table, tragedy accure!! *The
> > filter.filterRowKey can meet the deleted row*(I have post a mail before
> to
> > discribe this).
> > So if I try to skip the first 100 undeleted row, I user SkipFilter(100),
> > but infact it can only filter out 99 rows.
> > If I use this to do Paging, then at the second page I may meet the same
> row
> > from first page.
> >
> > Can someone give me some suggestions on it or how to design a better
> > SkipFilter to suit my need?
> > Thanks!
>