[jira] [Assigned] (CALCITE-4986) Make HepProgram thread-safe

["Julian Hyde (Jira)" <ji...@apache.org>]

     [ https://issues.apache.org/jira/browse/CALCITE-4986?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Julian Hyde reassigned CALCITE-4986:
------------------------------------

    Assignee: Julian Hyde

> Make HepProgram thread-safe
> ---------------------------
>
>                 Key: CALCITE-4986
>                 URL: https://issues.apache.org/jira/browse/CALCITE-4986
>             Project: Calcite
>          Issue Type: Bug
>            Reporter: Julian Hyde
>            Assignee: Julian Hyde
>            Priority: Major
>
> {{HepProgram}} uses mutable fields for its working state and is therefore not thread-safe. If two threads are planning queries simultaneously and are using the same {{HepProgram}} instances they might conflict with each other. I suspect that this happens several times in Calcite's standard set of rules.
> This change would move the mutable state out of {{HepProgram}}, so that {{HepProgram}} is fully immutable and therefore thread-safe.
> It would also modernize some of the internals; for instance, {{class HepInstruction.MatchLimit}} has a field {{int limit}} that could be made final and assigned in the constructor. 



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