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https://issues.apache.org/jira/browse/DRILL-5070?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Paul Rogers updated DRILL-5070:
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Comment: was deleted
(was: Analysis of impact. Method order is random. If a generated class has n
method, then there are n! possible orderings, and the cache holds up to n!
different variations when one would do. Reduction in each size for various
method counts (assuming each variation ends up being cached):
* 2 methods: 1/2
* 3 methods: 1/6
* 4 methods: 1/24
That is, a class with 3 methods will store 1/6 the number of variations after
the fix as before.
Since the cache is cluttered with fewer functionally duplicate classes, more
room will be available to preserve other classes, potentially further reducing
the amount of compilation required.)
> Code gen: create methods in fixed order to allow test verification
> ------------------------------------------------------------------
>
> Key: DRILL-5070
> URL: https://issues.apache.org/jira/browse/DRILL-5070
> Project: Apache Drill
> Issue Type: Bug
> Affects Versions: 1.8.0
> Reporter: Paul Rogers
> Priority: Minor
>
> A handy technique in testing is to compare generated code against a "golden"
> copy that defines the expected results. However, at present, Drill generates
> code using the method order returned by {{Class.getDeclaredMethods}}, but
> this method makes no guarantee about the order of the methods. The order
> varies from one run to the next. There is some evidence [this
> link|http://stackoverflow.com/questions/28585843/java-reflection-getdeclaredmethods-in-declared-order-strange-behaviour]
> that order can vary even within a single run, though a quick test was unable
> to reproduce this case.
> If method order does indeed vary within a single run, then the order can
> impact the Drill code cache since it compares the sources from two different
> generation events to detect duplicate code.
> This issue appeared when attempting to modify tests to capture generated code
> for comparison to future results. Even a simple generated case from
> {{ExpressionTest.testBasicExpression()}} that generates {{if(true) then 1
> else 0 end}} (all constants) produced methods in different orders on each
> test run.
> The fix is simple, in the {{SignatureHolder}} constructor, sort methods by
> name after retrieving them from the class. The sort ensures that method order
> is deterministic. Fortunately, the number of methods is small, so the sort
> step adds little cost.
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