[LUCENE-7966] build mr-jar and use some java 9 methods if available

• Type: Improvement
• Status: Closed
• Priority: Major
• Resolution: Fixed
• Fix Version/s: 7.3, 8.0
• Component/s: core/other, general/build
• Labels: Java9
• Lucene Fields: New
• Assignee: Uwe Schindler
• Reporter: Robert Muir
• Created: 12/Sep/17 05:23
• Updated: 28/Aug/22 15:19
• Resolved: 08/Feb/18 17:32

Description

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:

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

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.

Issue Links

• breaks: LUCENE-8156 patch-mrjar-classes fails if an old version of ASM is on the Ant classpath
• is related to: LUCENE-7968 AnalyzingSuggester's comparator compares incorrectly
• is related to: LUCENE-8154 TODO List when upgrading to Java 9 as minimum requirement
• is related to: LUCENE-8155 Add Java 9 support to smoke tester
• supercedes: LUCENE-3654 Optimize BytesRef comparator to use Unsafe long based comparison (when possible)