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

["Aleksey Yeschenko (JIRA)" <ji...@apache.org>]

     [ https://issues.apache.org/jira/browse/CASSANDRA-6167?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Aleksey Yeschenko resolved CASSANDRA-6167.
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    Resolution: Later

Closing as Later at least until someone comes up with a decent syntax (most likely UDF-based) for the feature. 

> Add end-slice termination predicate
> -----------------------------------
>
>                 Key: CASSANDRA-6167
>                 URL: https://issues.apache.org/jira/browse/CASSANDRA-6167
>             Project: Cassandra
>          Issue Type: Improvement
>          Components: CQL
>            Reporter: Tupshin Harper
>            Priority: Minor
>              Labels: cql
>
> 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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