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Posted to issues-all@impala.apache.org by "ASF subversion and git services (Jira)" <ji...@apache.org> on 2020/06/24 16:51:00 UTC
[jira] [Commented] (IMPALA-8755) Implement Z-ordering for Impala
[ https://issues.apache.org/jira/browse/IMPALA-8755?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17144042#comment-17144042 ]
ASF subversion and git services commented on IMPALA-8755:
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Commit 71a64591e35b5de818ca0cc1212b720d2e69c111 in impala's branch refs/heads/master from norbert.luksa
[ https://gitbox.apache.org/repos/asf?p=impala.git;h=71a6459 ]
IMPALA-8755: Unlock Z-ordering by default
Z-ordering has been around for a while behind a feature flag
(unlock_zorder_sort). It's around time to turn this flag on by default.
This commit beside setting the flag to true, merges the Z-order tests
from custom cluster tests into the normal test files.
Tests:
- Run all related tests.
Change-Id: I653e0e2db8f7bc2dd077943b3acf667514d45811
Reviewed-on: http://gerrit.cloudera.org:8080/16003
Reviewed-by: Impala Public Jenkins <im...@cloudera.com>
Tested-by: Impala Public Jenkins <im...@cloudera.com>
> Implement Z-ordering for Impala
> -------------------------------
>
> Key: IMPALA-8755
> URL: https://issues.apache.org/jira/browse/IMPALA-8755
> Project: IMPALA
> Issue Type: New Feature
> Reporter: Zoltán Borók-Nagy
> Assignee: Norbert Luksa
> Priority: Major
>
> Implement Z-ordering for Impala: [https://en.wikipedia.org/wiki/Z-order_curve]
> A Z-order curve defines an ordering on multi-dimensional data. Data sorted that way can be efficiently filtered by min/max statistics regarding to the columns participating in the ordering.
> Impala currently only supports lexicographic ordering via the SORT BY clause. This strongly prefers the first column, i.e. given the "SORT BY A, B, C" clause => A will be totally ordered (hence filtering on A will be very efficient), but values belonging to B and C will be scattered throughout the data set (hence filtering on B or C will barely do any good).
> We could add a new clause, e.g. a "ZSORT BY" clause to Impala that writes the data in Z-order.
> "ZSORT BY A, B C" would cluster the rows in a way that filtering on A, B, or C would be equally efficient.
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