Github user cloud-fan commented on a diff in the pull request:
https://github.com/apache/spark/pull/19594#discussion_r156388437
--- Diff:
sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/plans/logical/statsEstimation/EstimationUtils.scala
---
@@ -114,4 +115,183 @@ object EstimationUtils {
}
}
+ /**
+ * Returns overlapped ranges between two histograms, in the given value
range [newMin, newMax].
+ */
+ def getOverlappedRanges(
+ leftHistogram: Histogram,
+ rightHistogram: Histogram,
+ newMin: Double,
+ newMax: Double): Seq[OverlappedRange] = {
+ val overlappedRanges = new ArrayBuffer[OverlappedRange]()
+ // Only bins whose range intersect [newMin, newMax] have join
possibility.
+ val leftBins = leftHistogram.bins
+ .filter(b => b.lo <= newMax && b.hi >= newMin)
+ val rightBins = rightHistogram.bins
+ .filter(b => b.lo <= newMax && b.hi >= newMin)
+
+ leftBins.foreach { lb =>
+ rightBins.foreach { rb =>
--- End diff --
nit:
```
for {
leftBin <- leftBins
rightBin <- rightBins
} yield {
...
OverlappedRange ...
}
```
Then we can omit `val overlappedRanges = new ArrayBuffer[OverlappedRange]()`
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