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https://issues.apache.org/jira/browse/DRILL-3730?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14726115#comment-14726115
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Daniel Barclay (Drill) commented on DRILL-3730:
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> I would rather we did not change things that are not broken.
I'm trying to fix something that arguably _is_ broken:
{{TracingProxyDriver}} can trace calls across the rest of Drill's JDBC
interface because it can create proxy classes wrapping Drill's implementation
classes, since they are defined in terms of interfaces (e.g., JDBC's interface
{{java.sql.Connection}} and Drill's derived interface
{{org.apache.drill.jdbc.DrillConnection}}).
However, because {{DrillConnectionConfig}} is a class, the tracing proxy can't
create a proxy class wrapping it, and so can't trace calls to methods defined
on {{DrillConnectionConfig}} as it can for methods defined on other Drill JDBC
driver objects.
There doesn't seem to be any valid reason for that limitation and
inconsistency. (At deeper levels, we'd run into classes possibly with greater
justification for staying/being classes, but this {{DrillConnectionConfig}} is
in {{org.apache.drill.jdbc}}, not deeper in the system.)
Additionally, there's the simple inconsistency that most of the types (classes
or interfaces) in the rest of the Drill JDBC interface, other than those that
have to be classes (e.g., {{SQLException}} subclasses and the driver class),
are interfaces, but {{DrillConnectionConfig}} is not.
> I really don't see a good reason for changing all the classes to interfaces.
Please note that I'm proposing changing only one class in this JIRA report.
> One of the effects similar refactoring has had is that history is getting
> lost.
Perhaps there's a way to still record whatever part of history might actually
be important without sacrificing functionality (re proxying in this case),
usability (re this case's being in a published/external interface), and
maintainability / easy testability?
What types/forms or cases of history loss are you thinking of?
> Change JDBC driver's DrillConnectionConfig to interface
> -------------------------------------------------------
>
> Key: DRILL-3730
> URL: https://issues.apache.org/jira/browse/DRILL-3730
> Project: Apache Drill
> Issue Type: Bug
> Components: Client - JDBC
> Reporter: Daniel Barclay (Drill)
> Assignee: Daniel Barclay (Drill)
>
> Change {{org.apache.drill.jdbc.DrillConnectionConfig}} (in Drill's published
> interface for the JDBC driver) from being a class to being an interface.
> Move the implementation (including the inheritance from
> {{net.hydromatic.avatica.ConnectionConfigImpl}}) from published-interface
> package {{org.apache.drill.jdbc}} to a class in implementation package
> {{org.apache.drill.jdbc.impl}}.
> (See "TODO(DRILL-3730)" mark currently in DrillConnectionConfig.)
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