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Posted to issues@lucene.apache.org by "Tony Xu (Jira)" <ji...@apache.org> on 2020/06/08 22:59:00 UTC
[jira] [Commented] (LUCENE-9395) ConstantValuesSource creates more
than one DoubleValues unnecessarily
[ https://issues.apache.org/jira/browse/LUCENE-9395?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17128699#comment-17128699 ]
Tony Xu commented on LUCENE-9395:
---------------------------------
I believe the eager initialization would work for most cases.
> ConstantValuesSource creates more than one DoubleValues unnecessarily
> ----------------------------------------------------------------------
>
> Key: LUCENE-9395
> URL: https://issues.apache.org/jira/browse/LUCENE-9395
> Project: Lucene - Core
> Issue Type: Improvement
> Components: core/search
> Affects Versions: 8.5.2
> Reporter: Tony Xu
> Priority: Minor
>
> At my day job, we use ConstantValuesSource to represent default values or a constant query-level feature by calling *_DoubleValuesSource.constant_*. I realized under the hood the _*ConstantValuesSource.getDoubleValues*_ creates a new _*DoubleValues*_ which simply return the specified value each time it is called.
> Unless I missed something, I don't see a risk of creating one _*DoubleValues*_ as use it as the return value of all _*getDoubleValues**()*_ calls given that the constant _*DoubleValues*_ doesn't maintain any state.
> We can also offer the user flexibilities of how to initialize it.
> 1) _*DoubleValuesSource.constant(double constant)*_ – we can eagerly initialize an `DoubleValues` that returns the constant and make it the return value of all _*getDoubleValues()*_ calls.
> 2) _*DoubleValuesSource.constant(DoubleSupplier doubleSupplier)*_ – For lazy evaluation if the constant takes some time to compute and user expects the returned DVS will not be used in all code path.
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