On Tue, Mar 18, 2014 at 6:38 PM, Russ Weeks <[email protected]>wrote:
> Hi,
>
> org.apache.accumulo.core.iterators.user.RowFilter doesn't have a deepCopy
> method, which seems to mean that I can't chain multiple RowFilters together.
>
> Looking at some examples (GrepIterator, SortedKeyIterator) it seems pretty
> easy to provide an implementation of deepCopy, the only thing that concerns
> me is this part of the javadoc: "Creates a deep copy of this iterator *as
> though seek had not yet been called*". There are a bunch of conditions
> where RowFilter.skipRows will call seek() on the source iterator and
> decision iterator.
>
This is tricky. May need to open a ticket about making this easier. I
think RowFilter should have a protected constructor to aid w/ deepCopy().
If you need to implement deepCopy (you may not see comments below), then I
think you would need to do something like the following.
public class SomeRowFilter extends RowFilter {
private Map<String,String> options;
@Override
public SortedKeyValueIterator<Key,Value> deepCopy(IteratorEnvironment
env) {
SortedKeyValueIterator<Key,Value> dci = getSource().deepCopy(env);
SomeRowFilter srf = new SomeRowFilter();
srf.init(dci, options, env);
return srf;
}
@Override
public boolean acceptRow(SortedKeyValueIterator<Key,Value> rowIterator)
throws IOException {
// TODO Auto-generated method stub
return false;
}
@Override
public void init(SortedKeyValueIterator<Key,Value> source,
Map<String,String> options, IteratorEnvironment env) throws IOException {
super.init(source, options, env);
this.options = options;
}
}
>
> Is the missing implementation of deepCopy just an oversight or are there
> complications here? Where should I look to better understand how/when/why
> accumulo will call my iterator's deepCopy method?
>
Only a few iterators call deepCopy(). You can chain iterators that do not
implement deepCopy() w/ no problem as long as no iterator tries to call
it. For example, the IntersectingIterator calls deepCopy() in its init
method (so that it can have multiple independent pointers into a row). If
you wrapped a RowFilter with IntersectingIterator then your RowFilter would
need to implement deepCopy().
>
> Thanks,
> -Russ
>
