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https://issues.apache.org/jira/browse/NIFI-5855?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16703929#comment-16703929
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ASF GitHub Bot commented on NIFI-5855:
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GitHub user mattyb149 opened a pull request:
https://github.com/apache/nifi/pull/3191
NIFI-5855: Remove unnecessary ORDER BY clause in GenerateTableFetch when
Partition Size is zero
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You can merge this pull request into a Git repository by running:
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Alternatively you can review and apply these changes as the patch at:
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This closes #3191
----
commit 78a3c9badf4724691022081413bbb0a6de2f960e
Author: Matthew Burgess <mattyb149@...>
Date: 2018-11-29T22:46:24Z
NIFI-5855: Remove unnecessary ORDER BY clause in GenerateTableFetch when
Partition Size is zero
----
> Optimize GenerateTableFetch to remove unnecessary ORDER BY clause
> -----------------------------------------------------------------
>
> Key: NIFI-5855
> URL: https://issues.apache.org/jira/browse/NIFI-5855
> Project: Apache NiFi
> Issue Type: Improvement
> Components: Extensions
> Reporter: Matt Burgess
> Assignee: Matt Burgess
> Priority: Major
>
> Related to NIFI-5727, which for the query that GenerateTableFetch uses to get
> column/table information removes an unnecessary COUNT(*) clause when
> Partition Size = 0, the ORDER BY clause can also be removed. This is because
> there will be a single generated query that will fetch all rows that match
> the filters. The ORDER BY is necessary during pagination (when Partition Size
> > 0) so it can fetch from Row X to Row Y based on the row number, which is
> only constant if the column is ordered.
> This Jira proposes to remove the ORDER BY clause from the generated query if
> Partition Size is set to 0. Note that this can cause the output of the
> executed query to not guaranteed to be ordered; it is a possible change in
> behavior, but we don't document any guarantees about row ordering anyway. If
> the user needs the rows ordered, they can do it with QueryRecord, or they can
> add the ORDER BY clause manually via ReplaceText.
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