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https://issues.apache.org/jira/browse/SPARK-8008?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14567230#comment-14567230
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Rene Treffer commented on SPARK-8008:
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At the moment each partition uses it's own connection as far as I can tell, I
have to double check how this works on a cluster where even multiple server
might fetch data.
I'm currently loading year+month wise, due to DB schema (index on actual days,
locality based on year/month).
I don't think larger batches would be an solution. 3 months may require >160Mio
rows. I don't think batching that into one partition is a good idea.
> sqlContext.jdbc can kill your database due to high concurrency
> --------------------------------------------------------------
>
> Key: SPARK-8008
> URL: https://issues.apache.org/jira/browse/SPARK-8008
> Project: Spark
> Issue Type: Bug
> Reporter: Rene Treffer
>
> Spark tries to load as many partitions as possible in parallel, which can in
> turn overload the database although it would be possible to load all
> partitions given a lower concurrency.
> It would be nice to either limit the maximum concurrency or to at least warn
> about this behavior.
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