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Posted to commits@cassandra.apache.org by "Sylvain Lebresne (Created) (JIRA)" <ji...@apache.org> on 2012/01/27 15:36:15 UTC
[jira] [Created] (CASSANDRA-3798) get_count paging often asks for a
page uselessly
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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[jira] [Commented] (CASSANDRA-3798) get_count paging often asks for
a page uselessly
Posted by "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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[jira] [Updated] (CASSANDRA-3798) get_count paging often asks for a
page uselessly
Posted by "Sylvain Lebresne (Updated) (JIRA)" <ji...@apache.org>.
[ https://issues.apache.org/jira/browse/CASSANDRA-3798?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]
Sylvain Lebresne updated CASSANDRA-3798:
----------------------------------------
Attachment: 3798.patch
Patch attached against 1.1 (I don't really see a reason to risk back-porting to 1.0).
> 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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