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https://issues.apache.org/jira/browse/NIFI-2712?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15468533#comment-15468533
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ASF subversion and git services commented on NIFI-2712:
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Commit 2afc739ab72fa2bce8f64c8833f3eae1399966ce in nifi's branch
refs/heads/master from [~mattyb149]
[ https://git-wip-us.apache.org/repos/asf?p=nifi.git;h=2afc739 ]
NIFI-2712: Fixed Fetch processors for multiple max-value columns. This closes
#976
> Database Fetch processors' max-value columns don't work as expected
> -------------------------------------------------------------------
>
> Key: NIFI-2712
> URL: https://issues.apache.org/jira/browse/NIFI-2712
> Project: Apache NiFi
> Issue Type: Bug
> Reporter: Matt Burgess
> Assignee: Matt Burgess
>
> Currently, for QueryDatabaseTable and GenerateTableFetch, the user can enter
> any number of maximum-value columns, which are used to generate a SQL query
> that will fetch all records whose values are greater than the last-observed
> maximum values for those columns.
> However this makes multiple max-value columns not very useful, since they
> will both have to increase in lockstep or records will be lost/skipped. In
> such a case, using one or the other (but not both) would suffice, making
> multiple max-value columns useless.
> The more likely use case is that there are multiple columns whose values are
> strictly increasing, but at different rates. This is common with very large
> tables where a column could be for "date_created" and also a "bucket number"
> that strictly increases once a day. Queries for a day's worth of data are
> more efficient if they can be filtered on "bucket" (in this case), then on
> timestamp. However the generated SQL queries would have to reflect that
> "bucket" may remain the same as timestamp is increasing, but once the bucket
> value has increased, then only the (new) timestamps for that bucket should be
> fetched.
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