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From Eugene Cheipesh <echeip...@gmail.com>
Subject Re: Seeking Iterator
Date Fri, 09 Jan 2015 23:54:18 GMT
That’s would work well enough and is my next choice.

 The thought was, rows are stored in increasing order, so as long as I know when I walked
off the edge, and flag the iterator as empty it’d be good.  I’m just chasing the optimal
in this case, but if it doesn’t exist, oh well.

Thank you for the reference link, it’s very helpful. 

-- 
Eugene Cheipesh

From: Russ Weeks <rweeks@newbrightidea.com>
Reply: user@accumulo.apache.org <user@accumulo.apache.org>>
Date: January 9, 2015 at 6:48:47 PM
To: user@accumulo.apache.org <user@accumulo.apache.org>>
Subject:  Re: Seeking Iterator  

Hi, Eugene,

I think the conventional approach is to decompose your search area (bounding box?) into a
set of scan ranges that introduce minimal extraneous curve segments, and then pass all those
scan ranges into a BatchScanner. The excellent Accumulo Recipes site has an example[1]. Does
this approach not work for you?

In general, your custom iterator should never try to seek to a row id different from the current
row id, because that row could be hosted by a different tablet server.

-Russ

1: https://github.com/calrissian/accumulo-recipes/blob/master/store/geospatial-store/src/main/java/org/calrissian/accumulorecipes/geospatialstore/support/QuadTreeHelper.java#L33

On Fri, Jan 9, 2015 at 2:37 PM, Eugene Cheipesh <echeipesh@gmail.com> wrote:
Hello,

I am attempting to write an Iterator based on a Z-curve index to search through multi-dimensional
data. Essentially, given a record that I have encountered that is in the index range not in
the multi-demensional query range I have a way to generate the next candidate record, potentially
far ahead of the current point.

Ideally I would be able to refine my search range with subsequent calls to seek(). It appears
that Accumulo will create an iterator for every RFile (or some split other split point). The
beginning of the range argument to seek will be the record at beginning of this split (which
is good), however all instances of the iterator have the same, global range end (which is
bad).

I need to avoid the case where I seek past the range boundary of each individual iterator
instance and throw a NullPointerException. Is there any way to get enough information to achieve
this?

Thank you,

-- 
Eugene Cheipesh


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