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!
