GH-52: Make RangeEqualsVisitor of RunEndEncodedVector more efficient

[ViggoC]

What's Changed

Avoid doing a binary search on every step to make the RangeEqualsVisitor of RunEndEncodedVector more efficient.

Closes #52 .

[lidavidm]

Suggested change

	while (leftIterator.nextRun() | rightIterator.nextRun()) {
	while (leftIterator.nextRun() || rightIterator.nextRun()) {

[lidavidm]

I suppose we already checked the vector lengths to be equal, and since we're requiring run lengths to be equal, we don't need to check for any leftover runs after the loop?

[ViggoC]

@lidavidm The vector length is checked in RangeEqualsVisitor.rangeEqual. If we call vector.visit(RangeEqualsVisitor, Range)` directly, the argument checks are skipped. Using rangeEqual is the best practice, but we seem to be unable to limit users from using another method. Therefore, I'm also considering whether we need to add more boundary checks in Iterator. What do you think?

[lidavidm]

I think it doesn't hurt to make sure that both iterators are at the end at the end of the loop as a sanity check.

[ViggoC]

@lidavidm According to your suggestion, I should change it to while (leftIterator.nextRun() && rightIterator.nextRun()) instead of while (leftIterator.nextRun() || rightIterator.nextRun()). The short-circuit feature of '||' will make only leftIterator move forward, while right stays still.

[lidavidm]

Ah...that would be clearer over using the bitwise operator, yes

[lidavidm]

While the original code had this problem too, maybe it's better to check the run length first? That's presumably a cheaper check and so we can bail out earlier.

[ViggoC]

Modified as you suggested.

[lidavidm]

Ah, the linter is unhappy:

2025-05-21T23:24:02.6057815Z [WARN] /build/vector/src/main/java/org/apache/arrow/vector/complex/RunEndEncodedVector.java:833:5: Missing a Javadoc comment. [MissingJavadocMethod]
2025-05-21T23:24:02.6060058Z [WARN] /build/vector/src/main/java/org/apache/arrow/vector/complex/RunEndEncodedVector.java:850:5: Missing a Javadoc comment. [MissingJavadocMethod]
2025-05-21T23:24:02.6062203Z [WARN] /build/vector/src/main/java/org/apache/arrow/vector/complex/RunEndEncodedVector.java:864:5: Missing a Javadoc comment. [MissingJavadocMethod]

[ViggoC]

@lidavidm There were 15 checks that failed. Which ones do I need to fix? Which check action does the linter belong to?

[lidavidm]

All the checks run basically the same build, so you can check any one of them. The linter is part of running maven - did it not error locally?

[lidavidm]

Same deal. I can push a fix if that's ok?

 Error:  Failed to execute goal com.diffplug.spotless:spotless-maven-plugin:2.44.4:check (spotless-check) on project arrow-vector: The following files had format violations:
Error:      src/main/java/org/apache/arrow/vector/complex/RunEndEncodedVector.java
Error:          @@ -836,7 +836,8 @@
Error:           ·····*·@param·runEndEncodedVector·The·vector·to·iterate·over
Error:           ·····*·@param·startIndex·The·logical·start·index·of·the·range·(inclusive)
Error:           ·····*·@param·length·The·number·of·values·to·include·in·the·range
Error:          -·····*·@throws·IllegalArgumentException·if·startIndex·is·negative·or·(startIndex·+·length)·exceeds·vector·bounds
Error:          +·····*·@throws·IllegalArgumentException·if·startIndex·is·negative·or·(startIndex·+·length)·exceeds
Error:          +·····*·····vector·bounds
Error:           ·····*/
Error:           ····public·RangeIterator(RunEndEncodedVector·runEndEncodedVector,·int·startIndex,·int·length)·{
Error:           ······int·rangeEnd·=·startIndex·+·length;
Error:  Run 'mvn spotless:apply' to fix these violations.
Error:  -> [Help 1]
Error:  
Error:  To see the full stack trace of the errors, re-run Maven with the -e switch.
Error:  Re-run Maven using the -X switch to enable full debug logging.
Error:  
Error:  For more information about the errors and possible solutions, please read the following articles:
Error:  [Help 1] http://cwiki.apache.org/confluence/display/MAVEN/MojoExecutionException
Error:  
Error:  After correcting the problems, you can resume the build with the command
Error:    mvn <args> -rf :arrow-vector

[ViggoC]

@lidavidm Thank you, I applied the spotless, but most of the checks failed, seems it's terminated for some reason.

[lidavidm]

Retrying - I think GHA had an outage

[lidavidm]

And I think those JNI failures are unrelated...I'll have to find time and take a look.