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From Marc Parisi <m...@accumulo.net>
Subject Re: Using Iterator To Toss Unchanged Values
Date Thu, 12 Jul 2012 13:24:52 GMT
I read your question as William did, but I feel like what you may be doing
is looking to keep versions, and only exclude them when you desire, in
which case you could disable the VersioningIterator and only add it to your
iterator stack when you want to exclude them, thereby allowing you to keep
the versions for when you want to keep track or create metrics for them.

Am I misunderstanding your question?

Best Regards,
- Marco

On Thu, Jul 12, 2012 at 9:02 AM, William Slacum <wslacum@gmail.com> wrote:

> It seems like you're asking to create a new VersioningIterator so that
> you don't have to use the old one :) The VersioningIterator is pretty
> simple, so is there a reason you're not using it? Is there a
> difference in behavior with the DropUnchangedValueIterator and the
> VersioningIterator if it sees the same Key (save for timestamp) and
> Value?
>
> On Thu, Jul 12, 2012 at 8:47 AM, David Medinets
> <david.medinets@gmail.com> wrote:
> > I'd like to track field level changes for a given record (say,
> > author). So I create a table without a VersioningIterator. And I
> > insert a few records:
> >
> > insert "JOHN" "ATTRIBUTE" "AGE" "34"
> > insert "JOHN" "ATTRIBUTE" "HEIGHT" "67"
> > insert "JOHN" "BOOKS" "TITLE" "THE RISE OF ACCUMULO"
> >
> > The next action is that some ingest process happens and does this:
> >
> > insert "JOHN" "ATTRIBUTE" "AGE" "34"
> >
> > Since there is no VersioningIterator, there are two AGES both with
> > "34" as the value.
> >
> > I would like an DropUnchangedValueIterator which removes the last
> > inserted record. Removing the last record lets me use the n-1
> > timestamp as a LastUpdated value for the key-value pair. But as soon
> > as a record is deleted, the previous records are not available
> > anymore? What if the timestamp is set to MAX-timestamp so the records
> > are sorted backwards? Does that avoid the blocking tombstones? I'd
> > look at the source code before asking but I don't have that luxury for
> > the next week or two and the question is rattling around my head.
> >
> > Naturally, I could query the database before the ingest insert. But,
> > referring to slide 19 in Adam's presentation at
> > http://people.apache.org/~afuchs/slides/accumulo_table_design.pdf, the
> > read-modify-write design is not optimal.
>

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