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https://issues.apache.org/jira/browse/CALCITE-794?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15024581#comment-15024581
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Jesus Camacho Rodriguez commented on CALCITE-794:
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[~julianhyde], as we introduced AggregateJoinTransposeRule in Hive, we are
seeing huge stack calls for the {{areColumnsUnique}} method that lead to
slow/never-ending query compilation.
We have a temporary workaround to avoid that call in AggregateJoinTransposeRule
in Hive (HIVE-12508), but we should fix this problem from the root so we do not
hit it with other metadata providers.
Please, let me know the status (I saw there are some related issues such as
CALCITE-790 or CALCITE-604) and if you are working on these issues; otherwise,
I could start taking a look at them. Thanks
> Detect cycles when computing statistics
> ---------------------------------------
>
> Key: CALCITE-794
> URL: https://issues.apache.org/jira/browse/CALCITE-794
> Project: Calcite
> Issue Type: Bug
> Reporter: Julian Hyde
> Assignee: Julian Hyde
> Fix For: next
>
>
> The graph of RelNodes is allowed to be cyclic. This causes problems when
> evaluating certain metadata, for example RelMetataQuery.areColumnsUnique.
> While computing the value for RelNode r, it might recurse through say a
> Project and hit r again. This causes a stack overflow.
> We solve this by adding a map or set of active RelNodes. The map is stored
> within RelMetadataQuery, which can now be instantiated, and its methods are
> no longer static. The first call should instantiate a RelMetadataQuery, but
> all subsequent calls for metadata (perhaps several kinds of metadata) will
> use the same RelMetadataQuery instance, hence the same map.
> Also add a RelMetadataQuery argument to the static "handler" methods in
> RelMdColumnUniqueness and similar classes.
> This is a breaking change for people who have written a metadata handler, and
> might be subtle to detect, because the methods are invoked via reflection.
> For code that is just using RelMetadataQuery methods, the change is still
> breaking, but the break points and remedy will be obvious: the methods are no
> longer static, so they need to change RelMetadataQuery.foo() to
> RelMetadataQuery.instance().foo().
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