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https://issues.apache.org/jira/browse/NIFI-5855?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16703928#comment-16703928
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Matt Burgess commented on NIFI-5855:
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In addition to the check in NIFI-5727, we should remove the COUNT(*) when the
partition size is zero, for the same logical consequence (i.e. row count is not
used)
> 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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