incubator-accumulo-user mailing list archives

Site index · List index
Message view « Date » · « Thread »
Top « Date » · « Thread »
From Keith Turner <ke...@deenlo.com>
Subject Re: Finding my way through the forest of iterators
Date Wed, 15 Feb 2012 16:41:06 GMT
FYI,

I opened this ticket.

https://issues.apache.org/jira/browse/ACCUMULO-403

This may not help now, since it does not exist.  But your question
made me realize the we should probably implement a generalized row
selection iterator that works even if the row does not fit into
memory.


On Tue, Feb 14, 2012 at 11:39 AM, Benson Margulies
<bimargulies@gmail.com> wrote:
> Keith,
>
> I think I'm good with the simple filtering stuff right now. I'm aiming to
> make a second pass once 1.4 is released to revisit the problem of
> aggregation across CQ instead of only on Value.
>
> --benson
>
>
> On Tue, Feb 14, 2012 at 11:23 AM, Keith Turner <keith@deenlo.com> wrote:
>>
>> The WholeRowIterator is one way to do this.  One drawback is that it
>> reads entire rows into memory.
>>
>> If rows may not fit into memory there is an efficient way to handle
>> this using two iterators.  One iterator creates another iterator that
>> used to determine if rows contain the column, if not it seeks the
>> original iterator over the row. If using the second iterator you
>> determine the row contains the column, then you can read the row from
>> the original iterator. This design allows you to efficiently return
>> rows that meet a particular criteria w/o reading the rows into memory.
>>  If you are interested in learning more I can point you to examples in
>> the 1.4 code.
>>
>>
>> On Tue, Feb 14, 2012 at 9:54 AM, Benson Margulies <bimargulies@gmail.com>
>> wrote:
>> > I'm working with 1.3.5, and there's not a ton of javadoc in
>> > org.apache.accumulo.core.iterators.
>> >
>> > If I want to just filter to the rows that have a particular CF/CQ value,
>> > does one of the existing iterator classes do the job, or do I need to
>> > write
>> > one?
>> >
>
>

Mime
View raw message