[jira] [Resolved] (IMPALA-2066) Traverse expression trees iteratively

["Tim Armstrong (Jira)" <ji...@apache.org>]

     [ https://issues.apache.org/jira/browse/IMPALA-2066?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Tim Armstrong resolved IMPALA-2066.
-----------------------------------
    Resolution: Later

> Traverse expression trees iteratively
> -------------------------------------
>
>                 Key: IMPALA-2066
>                 URL: https://issues.apache.org/jira/browse/IMPALA-2066
>             Project: IMPALA
>          Issue Type: Improvement
>          Components: Frontend
>    Affects Versions: Impala 2.2
>            Reporter: Henry Robinson
>            Priority: Minor
>
> In several places, for example in {{Expr.analyze()}} in the frontend, we recursively traverse trees of expression objects. Doing so puts us at risk of blowing through the stack limit, and therefore having a much lower limit on the number of expressions than memory would actually allow (this is not just a theoretical improvement - users have been bumping up against this limit).
> We should transform our tree-walking code to iteratively traverse the exprs. For example, {{analyze()}} could be transformed into a post-order iterative traversal. Then the expr tree size is bounded by the size of stack we can reasonably allocate, which will be much larger than the call stack.



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