[jira] [Comment Edited] (CASSANDRA-6167) Add end-slice termination predicate

["Tupshin Harper (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/CASSANDRA-6167?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13901513#comment-13901513 ] 

Tupshin Harper edited comment on CASSANDRA-6167 at 2/14/14 2:56 PM:
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re: benedict

That certainly has some appeal. Linking to CASSANDRA-6561 for reference.

On the other hand, I'm increasingly a fan of scala/haskell style Either types, and if/when we get custom types, I would consider implementing this feature in terms such a disjoint union.


was (Author: tupshin):
That certainly has some appeal. Linking to CASSANDRA-6561 for reference.

On the other hand, I'm increasingly a fan of scala/haskell style Either types, and if/when we get custom types, I would consider implementing this feature in terms such a disjoint union.

> Add end-slice termination predicate
> -----------------------------------
>
>                 Key: CASSANDRA-6167
>                 URL: https://issues.apache.org/jira/browse/CASSANDRA-6167
>             Project: Cassandra
>          Issue Type: Improvement
>          Components: API, Core
>            Reporter: Tupshin Harper
>            Priority: Minor
>              Labels: ponies
>
> When doing performing storage-engine slices, it would sometimes be beneficial to have the slice terminate for other reasons other than number of columns or min/max cell name.
> Since we are able to look at the contents of each cell as we read it, this is potentially doable with very little overhead. 
> Probably more challenging than the storage-engine implementation itself, is to come up with appropriate CQL syntax (Thrift, should we decide to support it, would be trivial).
> Two possibilities ar
> 1) special where function:
> SELECT pk,event from cf WHERE pk IN (1,5,10,11) AND partition_predicate({predicate})
> or a bigger language change, but i think one I prefer. more like:
> 2) SELECT pk,event from cf where pk IN (1,5,10,11) UNTIL PARTITION event {predicate}
> Neither feels perfect, but I do like the fact that the second one at least clearly states what it is intended to do.
> By using "UNTIL PARTITION", we could re-use the UNTIL keyword to handle other kinds of early-termination of selects that the coordinator might be able to do, such as stop retrieving additional rows from shards after a particular criterion was met.



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