uros-b opened a new pull request, #57883:
URL: https://github.com/apache/spark/pull/57883
### What changes were proposed in this pull request?
Uses the idiomatic emptiness checks for the three `ArrayBuffer` length
comparisons in `ExternalAppendOnlyMap`:
```scala
if (kcPairs.nonEmpty) { // was kcPairs.length > 0
def isEmpty: Boolean = pairs.isEmpty // was pairs.length == 0
assert(pairs.nonEmpty) // was assert(pairs.length > 0)
```
### Why are the changes needed?
The same file already uses this form for its other emptiness checks
(`spilledMaps.isEmpty`, `mergeHeap.nonEmpty`, `mergeHeap.isEmpty`), as does the
sibling `ExternalSorter`, so these three were the odd ones out.
To be clear about scope: this is a **readability change, not a performance
optimization**. For `ArrayBuffer` both forms are O(1) and exactly equivalent --
`isEmpty` resolves to `SeqOps.isEmpty`, which is `lengthCompare(0) == 0` over
the buffer's cached size -- so there is no measurable difference either way.
The `currentMap.size > 0` check in `forceSpill` is deliberately **not**
changed. `AppendOnlyMap` is an `Iterable` rather than a `Seq` and does not
override `knownSize`, so `isEmpty` there would fall through to `iterator()`,
which asserts the map has not been destructively sorted. Since `forceSpill` can
run under memory pressure after `destructiveSortedIterator` has been called,
that site must stay a size comparison.
### Does this PR introduce _any_ user-facing change?
No.
### How was this patch tested?
Behavior-preserving, so the existing `ExternalAppendOnlyMapSuite` coverage
applies, in particular the spill and hash-collision tests that drive
`StreamBuffer` with more than one pair per hash. The three predicates have
identical truth values for every possible buffer state, so no branch can be
taken differently.
### Was this patch authored or co-authored using generative AI tooling?
Generated-by: Claude Code (Opus 4.8)
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