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https://issues.apache.org/jira/browse/BEAM-3424?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Alexey Romanenko reassigned BEAM-3424:
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Assignee: Alexey Romanenko (was: Jean-Baptiste Onofré)
> CassandraIO uses 1 split if can't estimate size
> -----------------------------------------------
>
> Key: BEAM-3424
> URL: https://issues.apache.org/jira/browse/BEAM-3424
> Project: Beam
> Issue Type: Bug
> Components: io-java-cassandra
> Reporter: Eugene Kirpichov
> Assignee: Alexey Romanenko
> Priority: Major
>
> See
> https://stackoverflow.com/questions/48090668/how-to-increase-dataflow-read-parallelism-from-cassandra?noredirect=1#comment83227824_48090668
> . When CassandraIO can't estimate size, it falls back to a single split:
> https://github.com/apache/beam/blob/master/sdks/java/io/cassandra/src/main/java/org/apache/beam/sdk/io/cassandra/CassandraServiceImpl.java#L196
> A single split is very poor for performance. We should fall back to a
> different value. Not sure what a good value would be; probably the largest
> value that still doesn't introduce too much per-split overhead? E.g. would
> there be any downside to just changing that number to 100?
> Alternatively/additionally, like in DatastoreIO, CassandraIO could accept
> requested number of splits as a parameter.
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