That's an interesting approach. I'll try it ... Accept my deepest
thanks

One thing comes to my mind when I need a double filtration, i.e 2
operations to remove duplicates.
For example first one by name
Then remove duplicates by address

Can you order the output of an operation to feed the second
operation ?


On Nov 30, 3:30 pm, Miles Waller <[email protected]> wrote:
> Hi,
>
> I haven't tried the AbstractAggregationOperation before, but the way
> I've done this in the past is to ensure the input source is sorted at the
> outset, so the duplicates all follow each other in the rowset.  Then create
> a custom Operation that always "remebers" the last yielded row (or just the
> key value), and yields subsequent rows only if they differ in the key
> columns, or drops them if they are duplicates.  I haven't tested, but the
> memory footprint for the operation should just be the one remembered row.
>
> You could avoid sorting the input if you kept a list of key values in the
> Operation, but that's more memory for a large set.
>
> Hope that helps,
>
> Miles
>
> On Tue, Nov 30, 2010 at 12:00 PM, jalchr <[email protected]> wrote:
> > Now, I'm using the AbstractAggregationOperation which aggregates all
> > rows based on some Column(s) ... This works fine but it results it
> > huge memory consumption ...
>
> > What is the best, efficient way (least memory possible) to use when
> > trying to filter the rows based on some column combination (for
> > example FirstName, LastName) ...
>
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