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Posted to issues@lucene.apache.org by "Haoyu Zhai (Jira)" <ji...@apache.org> on 2020/07/01 18:14:00 UTC
[jira] [Commented] (LUCENE-8574) ExpressionFunctionValues should
cache per-hit value
[ https://issues.apache.org/jira/browse/LUCENE-8574?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17149623#comment-17149623 ]
Haoyu Zhai commented on LUCENE-8574:
------------------------------------
[~mikemccand] Yes it fixes the test case. Before the fix the test will cause {{OutOfMemoryException}} and after the fix it finishes in a reasonable time (like < 1s when I run it solely)
Thanks for reviewing that, I've addressed those comments!
> ExpressionFunctionValues should cache per-hit value
> ---------------------------------------------------
>
> Key: LUCENE-8574
> URL: https://issues.apache.org/jira/browse/LUCENE-8574
> Project: Lucene - Core
> Issue Type: Bug
> Affects Versions: 7.5, 8.0
> Reporter: Michael McCandless
> Assignee: Robert Muir
> Priority: Major
> Attachments: LUCENE-8574.patch, unit_test.patch
>
> Time Spent: 2h
> Remaining Estimate: 0h
>
> The original version of {{ExpressionFunctionValues}} had a simple per-hit cache, so that nested expressions that reference the same common variable would compute the value for that variable the first time it was referenced and then use that cached value for all subsequent invocations, within one hit. I think it was accidentally removed in LUCENE-7609?
> This is quite important if you have non-trivial expressions that reference the same variable multiple times.
> E.g. if I have these expressions:
> {noformat}
> x = c + d
> c = b + 2
> d = b * 2{noformat}
> Then evaluating x should only cause b's value to be computed once (for a given hit), but today it's computed twice. The problem is combinatoric if b then references another variable multiple times, etc.
> I think to fix this we just need to restore the per-hit cache?
>
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