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Accumulo, mail # user - Using Iterator To Toss Unchanged Values


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David Medinets 2012-07-12, 12:47
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Re: Using Iterator To Toss Unchanged Values
William Slacum 2012-07-12, 13:02
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
<[EMAIL PROTECTED]> 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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Marc Parisi 2012-07-12, 13:24
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Billie J Rinaldi 2012-07-12, 15:47
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Corey Nolet 2012-07-12, 19:07
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David Medinets 2012-07-12, 19:09