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Posted to issues@lucene.apache.org by "Michael McCandless (Jira)" <ji...@apache.org> on 2021/01/16 12:35:00 UTC
[jira] [Updated] (LUCENE-8574) ExpressionFunctionValues should
cache per-hit value
[ https://issues.apache.org/jira/browse/LUCENE-8574?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]
Michael McCandless updated LUCENE-8574:
---------------------------------------
Fix Version/s: 8.7
master (9.0)
> 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
> Fix For: master (9.0), 8.7
>
> Attachments: LUCENE-8574.patch, unit_test.patch
>
> Time Spent: 3h 20m
> 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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