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https://issues.apache.org/jira/browse/LUCENE-7966?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16170377#comment-16170377
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Uwe Schindler commented on LUCENE-7966:
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I implemented by latest idea based again on Robert's patch:
https://github.com/apache/lucene-solr/compare/master...uschindler:jira/LUCENE-7966-v2
This approach is much more clean: We compile against Robert's replacement
classes {{FutureObjects}} and {{FutureArrays}} (that have to contain the same
method signatures as the Java 9 original, but we can add a test for this later
with smoketester) as usual with Java 8. Before packaging the JAR file we read
all class files and patch all {{FutureObjects/FutureArrays}} references to
refer to the Java 9 class. The patched output is sent to a separate folder
{{build/classes/java9}}. The JAR file is then packaged to take both variants,
placing the patched ones in the Java 9 MultiRelease part.
Currently only the lucene-core.jar file uses the patched stuff, so stuff
outside lucene-core (e.g., codecs) does not yet automatically add Java 9
variants, instead it will use Robert's classes. If this is the way to go, I
will move the patcher to the global tools directory and we can apply patching
to all JAR files of the distribution. WARNING: We cannot support Maven builds
here, Maven always builds a Java8-only JAR file!
[~mikemccand], [~jpountz]: Could you build a lucene-core.jar file with the
above branch on Github and do your tests again? The main difference here is
that the JAR file no longer contains a delegator class. Instead all class files
that were originally compiled with FutureObjects/FutureArrays (for Java 8
support) are patched to directly use the Java 9 Arrays/Objects methods, without
using a delegator class. Keep in mind: This currently only support
lucene-core.jar, the codecs JAR file is not yet Multirelease with this patch.
> build mr-jar and use some java 9 methods if available
> -----------------------------------------------------
>
> Key: LUCENE-7966
> URL: https://issues.apache.org/jira/browse/LUCENE-7966
> Project: Lucene - Core
> Issue Type: Improvement
> Components: general/build
> Reporter: Robert Muir
> Attachments: LUCENE-7966.patch, LUCENE-7966.patch, LUCENE-7966.patch,
> LUCENE-7966.patch, LUCENE-7966.patch
>
>
> See background: http://openjdk.java.net/jeps/238
> It would be nice to use some of the newer array methods and range checking
> methods in java 9 for example, without waiting for lucene 10 or something. If
> we build an MR-jar, we can start migrating our code to use java 9 methods
> right now, it will use optimized methods from java 9 when thats available,
> otherwise fall back to java 8 code.
> This patch adds:
> {code}
> Objects.checkIndex(int,int)
> Objects.checkFromToIndex(int,int,int)
> Objects.checkFromIndexSize(int,int,int)
> Arrays.mismatch(byte[],int,int,byte[],int,int)
> Arrays.compareUnsigned(byte[],int,int,byte[],int,int)
> Arrays.equal(byte[],int,int,byte[],int,int)
> // did not add char/int/long/short/etc but of course its possible if needed
> {code}
> It sets these up in {{org.apache.lucene.future}} as 1-1 mappings to java
> methods. This way, we can simply directly replace call sites with java 9
> methods when java 9 is a minimum. Simple 1-1 mappings mean also that we only
> have to worry about testing that our java 8 fallback methods work.
> I found that many of the current byte array methods today are willy-nilly and
> very lenient for example, passing invalid offsets at times and relying on
> compare methods not throwing exceptions, etc. I fixed all the instances in
> core/codecs but have not looked at the problems with AnalyzingSuggester. Also
> SimpleText still uses a silly method in ArrayUtil in similar crazy way, have
> not removed that one yet.
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