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Date: Fri, 27 Jan 2012 14:36:15 +0000 (UTC)
From: "Sylvain Lebresne (Created) (JIRA)" <jira@apache.org>
To: commits@cassandra.apache.org
Message-ID: <1685841153.47.1327674975219.JavaMail.tomcat@hel.zones.apache.org>
Subject: [jira] [Created] (CASSANDRA-3798) get_count paging often asks for a
 page uselessly
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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


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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