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https://issues.apache.org/jira/browse/CASSANDRA-1337?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13292395#comment-13292395
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David Alves commented on CASSANDRA-1337:
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couple of questions:
- If i got the logic right the point is that we keep creating async handlers
until we exceed concurrency factor, at which time we block and wait for the
replies, clear the handlers and start again. Can't we reach a state where we
have handlers to which we haven't called get() (because they have not exceeded
concurrecy factor?).
- On another matter what would be the best strategy to test this both for
correctness and speed?
> parallelize fetching rows for low-cardinality indexes
> -----------------------------------------------------
>
> Key: CASSANDRA-1337
> URL: https://issues.apache.org/jira/browse/CASSANDRA-1337
> Project: Cassandra
> Issue Type: Improvement
> Reporter: Jonathan Ellis
> Assignee: David Alves
> Priority: Minor
> Fix For: 1.2
>
> Attachments:
> 0001-CASSANDRA-1337-scan-concurrently-depending-on-num-rows.txt,
> CASSANDRA-1337.patch
>
> Original Estimate: 8h
> Remaining Estimate: 8h
>
> currently, we read the indexed rows from the first node (in partitioner
> order); if that does not have enough matching rows, we read the rows from the
> next, and so forth.
> we should use the statistics fom CASSANDRA-1155 to query multiple nodes in
> parallel, such that we have a high chance of getting enough rows w/o having
> to do another round of queries (but, if our estimate is incorrect, we do need
> to loop and do more rounds until we have enough data or we have fetched from
> each node).
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