[jira] Commented: (CONNECTORS-110) Max activity and Max bandwidth reports fail under Derby with a stack trace

["Karl Wright (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/CONNECTORS-110?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12912212#action_12912212 ] 

Karl Wright commented on CONNECTORS-110:
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Checked in a partial solution to this issue.  At least the reports don't fail with an exception now, but they also list all time intervals on Derby instead of collapsing and reporting just the maximum, which will make these reports far less useful.  r998635.

> Max activity and Max bandwidth reports fail under Derby with a stack trace
> --------------------------------------------------------------------------
>
>                 Key: CONNECTORS-110
>                 URL: https://issues.apache.org/jira/browse/CONNECTORS-110
>             Project: Apache Connectors Framework
>          Issue Type: Bug
>          Components: Framework crawler agent
>            Reporter: Karl Wright
>
> The reason for the failure is because the queries used are doing the Postgresql DISTINCT ON (xxx) syntax, which Derby does not support.  Unfortunately, there does not seem to be a way in Derby at present to do anything similar to DISTINCT ON (xxx), and the queries really can't be done without that.
> One option is to introduce a getCapabilities() method into the database implementation, which would allow ACF to query the database capabilities before even presenting the report in the navigation menu in the UI.  Another alternative is to do a sizable chunk of resultset processing within ACF, which would require not only the DISTINCT ON() implementation, but also the enclosing sort and limit stuff.  It's the latter that would be most challenging, because of the difficulties with i18n etc.

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