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https://issues.apache.org/jira/browse/CALCITE-2267?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Julian Hyde resolved CALCITE-2267.
----------------------------------
       Resolution: Fixed
    Fix Version/s: 1.17.0

Fixed in 
[f5b041ff|http://git-wip-us.apache.org/repos/asf/calcite/commit/f5b041ff]; 
thanks for the PR, [~zhong.j.yu]!

> AbstractRelNode.getId() may produce duplicate IDs in multi-threaded 
> environment
> -------------------------------------------------------------------------------
>
>                 Key: CALCITE-2267
>                 URL: https://issues.apache.org/jira/browse/CALCITE-2267
>             Project: Calcite
>          Issue Type: Bug
>          Components: core
>            Reporter: Zhong Yu
>            Assignee: Julian Hyde
>            Priority: Major
>             Fix For: 1.17.0
>
>
> RelOptNode.getId() is supposed to be unique per instance; however, the 
> generation of AbstractRelNode.id is not thread safe; in a multithreaded 
> environment, the behavior is undeterministic, and there is a non-trivial 
> possibility that duplicate IDs are generated for different nodes.
> This ID is used for comparing nodes in several places, therefore it may 
> affect program stability and correctness. For example, if we set id=0 for all 
> nodes, Calcite's own test suite will have multiple failures. 
> In our own test environment, the optimizers are expected to be deterministic, 
> yet occasionally they mysteriously produce different plans. While we cannot 
> be 100% sure that it is caused by AbstractRelNode.id, we can verify that 
> fudging with the ID will reliably change the output of our optimizers.



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