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https://issues.apache.org/jira/browse/NIFI-5855?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Pierre Villard updated NIFI-5855:
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Description:
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.
was:
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.
> 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
> Fix For: 1.9.0
>
>
> 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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