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Accumulo >> mail # user >> Iterators and seeking the middle of a row

Cardon, Tejay E 2012-09-13, 19:50
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Re: Iterators and seeking the middle of a row
On Thu, Sep 13, 2012 at 3:50 PM, Cardon, Tejay E
> The javadoc for SortedKeyValueIterator.seek states:
> “Iterators that examine groups of adjacent key/value pairs (e.g. rows) to
> determine their top key and value should be sure that they properly handle a
> seek to a key in the middle of such a group (e.g. the middle of a row). Even
> if the client always seeks to a range containing an entire group (a,c), the
> tablet server could send back a batch of entries corresponding to (a,b],
> then reseek the iterator to range (b,c) when the scan is continued.”
> However, it gives no indication of what proper handling is.  What should an
> iterator that considers and entire row do in this case?  Does it simply
> ignore the row?  Attempt to seek its source iterator to the full row of the
> first range?  I’m struggling to understand the best approach here.

org.apache.accumulo.core.iterators.user.RowFilter does what you
suggested.  It seeks to the beggining of a row if the range starts in
the middle of the row.  Look at the javadoc for the row filter, it
discusses the seeking behavior.

> In my specific case, if it matters, I’m largely looking for ColumnQualifiers
> which exist in all Column Families in a given set (intersecting iterator,
> sortof).
> Thanks,
> Tejay
William Slacum 2012-09-13, 22:34
William Slacum 2012-09-13, 22:38