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From Keith Turner <ke...@deenlo.com>
Subject Re: [jira] [Commented] (ACCUMULO-227) Improve in memory map counts to provide cell level uniqueness for repeated columns in mutation
Date Thu, 22 Dec 2011 22:09:05 GMT
On Thu, Dec 22, 2011 at 4:49 PM, Aaron Cordova <aaron@cordovas.org> wrote:
> I think it's fine to consider different versions of 'identical keys', meaning row,colfam,colqual,
because in that case the implementation still treats two keys that only differ by timestamp
as two unique keys. But I don't think we should allow multiple identical _versions_ of identical
keys, to use your terminology. I think we should throw all but one away if the user does happen
to try to insert them and if the user wants to aggregate across values, he or she must use
different version numbers or timestamps or whatever.
>
> If generating unique timestamps within mutations that want to perform several updates
to the same row,colfam,colqual is a problem, why don't we allow the user to 'put()' multiple
updates into a mutation, and on the server then assign slightly different timestamps to the
identical row,colfam,colqual triples that are found in a mutation. Would that make everyone
happy?

This still does not address the issue of separate mutations inserting
the exact same key.  Also timestamps are only set on the keys in a
mutation if the user does not set them.

So if a table comes to have multiple keys that are exactly the same,
what do you propose?  That we drop them?  Which one will you drop?
One nice thing about Accumulo is that if you wish to have this
behavior, you can very easily write an iterator to do it.  I think you
are proposing that we configure an iterator to do this by default?

I think if the user is inserting things with exact same key and
expecting it to behave like a treemap (honor order of arrival), then
it never will.  Even if we drop duplicate keys, we will not achieve
the map behavior you described.

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