Hi All
One thing came while going through Filter code
Suppose I am using a FilterList along with my Scan. The list contains one
PageFilter(max pages=N) and one SingleColumnValueFilter.[One filter checks a
col value and other deals with number of rows in result] So as a user what I
expect out of this usage is to get N number of rows where colval=X
Now if I create my FilterList like below things would work fine
FilterList list = new FilterList();
SingleColumnValueFilter f = new SingleColumnValueFilter(..)
f.setLatestVersionOnly(false);
list.add( f);
list.add( new PageFilter(..));
Just use the code with slight diff in the order in which the filters are added
FilterList list = new FilterList();
list.add( new PageFilter(..));
SingleColumnValueFilter f = new SingleColumnValueFilter(..)
f.setLatestVersionOnly(false);
list.add( f);
Being a user I would expect to get the same result. But it may not be. This
even can return me empty results also.
Here as the filter which deals with the number of returned rows coming 1st. So
even if the second filter might filter out one KV or row later, this number
tracked within the filter getting incremented. [1st filter never gets a chance
to rollback the operation when the next filter filters out the row/KV]
If we use like the 1st way in which the filters dealing with the number of rows
or KVs as the last items in the FilterList, there wont be any problem. Do some
one feel this as an issue with our filter framework and FilterList ? Atleast
we should document this clearly I think. Pls give your suggestion.
Note : In the above shown code sample if we are going with latet version
only=true for SingleColumnValueFilter , even the second scenario also will be
working fine. Here the diff would be skipping one row will be handled by the
filterRowKey() itself and filterRow() wont get called for the ignored
rowkey.[PageFilter deals with filterRow()]
So it all depends on which of the APIs the filter is using to decide to include
or skip or seek to rows.
Also there is one issues opened regarding the FilterList HBASE-6132 Pls
give your valuable thoughts and suggestions
-Anoop-
