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https://issues.apache.org/jira/browse/CALCITE-604?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Julian Hyde resolved CALCITE-604.
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Resolution: Fixed
Fix Version/s: 1.7.0
Fixed in http://git-wip-us.apache.org/repos/asf/calcite/commit/d14040c5.
> Invoke metadata providers via a class generated at runtime, rather than
> reflection
> ----------------------------------------------------------------------------------
>
> Key: CALCITE-604
> URL: https://issues.apache.org/jira/browse/CALCITE-604
> Project: Calcite
> Issue Type: Bug
> Reporter: Julian Hyde
> Assignee: Julian Hyde
> Fix For: 1.7.0
>
>
> Currently we dispatch to metadata providers using reflection. With this
> change, we generate a dispatcher class and compile using Janino.
> Currently calls to metadata providers are dispatched via reflection
> (Method.invoke, see ReflectiveRelMetadataProvider, ChainedRelMetadataProvider
> and CachingInvocationHandler), and I suspect that planning a complex query
> (especially with tracing enabled) makes millions of calls. Reflection has a
> performance problem; lots of boxing and unboxing and creating temporary
> arrays and bound objects.
> One option we considered to improve performance was moving to MethodHandle.
> (JDK 1.7 introduced
> http://docs.oracle.com/javase/7/docs/api/java/lang/invoke/MethodHandle.html,
> a more efficient way to invoke methods. Access control etc. is done when the
> handle is created, not each invocation.) However, MethodHandle.invoke can
> dispatch only within one provider.
> So, we should generate a dispatcher class, and compile and instantiate at run
> time using Janino.
> For each metadata interface we will need to add a handler interface that has
> the same methods but two extra arguments (a sub-class of RelNode, and a
> RelMetadataQuery). Previously these arguments were passed by calling "bind"
> on an UnboundMetadata.
> We can also make the dispatcher cache the results within a metadata call.
> This should yield a performance improvement when, say, a join requires many
> kinds of metadata (rowCount, averageRowSize, selectivity) and they all rely
> on the rowCount of the input, and that rowCount is expensive to compute.
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