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From Lance Norskog <>
Subject Re: DIH: alternative approach to deltaQuery
Date Fri, 17 Sep 2010 03:40:43 GMT
Database optimization is not like program optimization- it is wildly 

What bugs me about the delta approach is using the last time DIH ran, 
rather than a timestamp from the DB. Oh well. Also, with SOLR-1499 you 
can query Solr directly to see what it has.

Lukas Kahwe Smith wrote:
> Hi,
> I think i have mentioned this approach before on this list, but I really think that the
deltaQuery approach which is currently explained as the "way to do updates" is far from ideal.
It seems to add a lot of redundant queries.
> I therefore propose to merge the initial import and delta queries using the below approach:
>          <entity name="person" query="SELECT * FROM foo
>          WHERE '${dataimporter.request.clean}' != 'false' OR last_updated>  '${dataimporter.last_index_time}'">
> Using this approach when clean = true the "last_updated>  '${dataimporter.last_index_time}"
should be optimized out by any sane RDBMS. And if clean = false it basically triggers the
delta query part to be evaluated.
> Is there any downside to this approach? Should this be added to the wiki?
> regards.
> Lukas Kahwe Smith

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