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From Thomas Downing <tdown...@proteus-technologies.com>
Subject How to delete rows in a FIFO manner
Date Fri, 06 Aug 2010 12:50:04 GMT

Continuing with testing HBase suitability in a high ingest rate
environment, I've come up with a new stumbling block, likely
due to my inexperience with HBase.

We want to keep and purge records on a time basis: i.e, when
a record is older than say, 24 hours, we want to purge it from
the database.

The problem that I am encountering is the only way I've found
to delete records using an arbitrary but strongly ordered over
time row id is to scan for rows from lower bound to upper
bound, then build an array of Delete using

for Result in ResultScanner
     add new Delete( Result.getRow( ) ) to Delete array.

This method is far too slow to keep up with our ingest rate; the
iteration over the Results in the ResultScanner is the bottleneck,
even though the Scan is limited to a single small column in the
column family.

The obvious but naive solution is to use a sequential row id
where the lower and upper bound can be known.  This would
allow the building of the array of Delete objects without a scan
step.  Problem with this approach is how do you guarantee a
sequential and non-colliding row id across more than one Put'ing
process, and do it efficiently.  As it happens, I can do this, but
given the details of my operational requirements, it's not a simple
thing to do.

So I was hoping that I had just missed something.  The ideal
would be a Delete object that would take row id bounds in the
same way that Scan does, allowing the work to be done all
on the server side.  Does this exists somewhere?  Or is there
some other way to skin this cat?


Thomas Downing

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