Github user cloud-fan commented on a diff in the pull request:
https://github.com/apache/spark/pull/23214#discussion_r238549645
--- Diff:
sql/core/src/main/scala/org/apache/spark/sql/execution/joins/HashedRelation.scala
---
@@ -398,8 +399,8 @@ private[execution] final class LongToUnsafeRowMap(val
mm: TaskMemoryManager, cap
private var numKeys = 0L
// Tracking average number of probes per key lookup.
- private var numKeyLookups = 0L
- private var numProbes = 0L
+ private var numKeyLookups = new LongAdder
+ private var numProbes = new LongAdder
--- End diff --
I'm surprised. I think `LongToUnsafeRowMap` is used in a single thread
environment and multi-thread contend should not be an issue here. Do you have
any insights about how this fixes the perf issue?
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