[jira] [Commented] (CASSANDRA-3798) get_count paging often asks for a page uselessly

["Jonathan Ellis (Commented) (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/CASSANDRA-3798?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13194818#comment-13194818 ] 

Jonathan Ellis commented on CASSANDRA-3798:
-------------------------------------------

+1
                
> get_count paging often asks for a page uselessly
> ------------------------------------------------
>
>                 Key: CASSANDRA-3798
>                 URL: https://issues.apache.org/jira/browse/CASSANDRA-3798
>             Project: Cassandra
>          Issue Type: Improvement
>    Affects Versions: 1.0.0
>            Reporter: Sylvain Lebresne
>            Assignee: Sylvain Lebresne
>            Priority: Minor
>             Fix For: 1.1
>
>         Attachments: 3798.patch
>
>
> Current get_count paging stopping condition is:
> {noformat}
> if ((requestedCount == 0) || ((columns.size() == 1) && (lastName.equals(predicate.slice_range.start))))
> {
>     break;
> }
> {noformat}
> On a "count how many columns this row has" query (arguably the main reason why you'd use get_count), requestedCount will never be 0, and so we'll stop whenever a page has only returned the last column of the preceding page. While this isn't wrong, we could stop as soon as a page returns less element than requested and avoid querying that last 1 column page.

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