maropu commented on a change in pull request #32498:
URL: https://github.com/apache/spark/pull/32498#discussion_r631512825
##########
File path:
sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/plans/logical/basicLogicalOperators.scala
##########
@@ -789,6 +793,36 @@ case class Range(
}
}
+ private def getHistogramStatistics = {
+ val numBins = conf.histogramNumBins
+ val height = numElements.toDouble / numBins
+ val percentileArray = (0 to numBins).map(i => i * height).toArray
+
+ var binId = 0
Review comment:
This is not performance-intensive code, so could you use
`zipWithIndex+map` instead of `while`?
##########
File path:
sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/plans/logical/basicLogicalOperators.scala
##########
@@ -789,6 +793,36 @@ case class Range(
}
}
+ private def getHistogramStatistics = {
+ val numBins = conf.histogramNumBins
+ val height = numElements.toDouble / numBins
+ val percentileArray = (0 to numBins).map(i => i * height).toArray
+
+ var binId = 0
+ val binArray = new Array[HistogramBin](numBins)
+ var lowerIndex = percentileArray(0)
+ var lowerBinValue = getRangeValue(0)
+ while (binId < numBins) {
+ val upperIndex = percentileArray(binId + 1)
+ val upperBinValue = getRangeValue(math.max(math.ceil(upperIndex).toInt -
1, 0))
+ val ndv = math.max(math.ceil(upperIndex).toInt -
math.ceil(lowerIndex).toInt, 1)
Review comment:
Please do not repeat `math.ceil(upperIndex)` here.
##########
File path:
sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/plans/logical/basicLogicalOperators.scala
##########
@@ -789,6 +793,36 @@ case class Range(
}
}
+ private def getHistogramStatistics = {
Review comment:
`getHistogramStatistics` -> `computeHistogramStatistics()`
##########
File path:
sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/plans/logical/basicLogicalOperators.scala
##########
@@ -774,13 +774,17 @@ case class Range(
} else {
(start + (numElements - 1) * step, start)
}
+
+ val histogram = getHistogramStatistics
Review comment:
I feel its better to wrap a return value of `computeHistogramStatistics
` with `Some` in the caller side because the method always return a value.
https://github.com/apache/spark/pull/32498/files#diff-0ac2c89f8cc0d00e8fe7717b01697f36f20fe8abf2def09bcfde0ad84b30e467R814
##########
File path:
sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/plans/logical/basicLogicalOperators.scala
##########
@@ -774,13 +774,17 @@ case class Range(
} else {
(start + (numElements - 1) * step, start)
}
+
+ val histogram = getHistogramStatistics
Review comment:
Let's check `conf.histogramEnabled` here;
```
val histogram = if (conf.histogramEnabled) {
Some(computeHistogramStatistics())
} else {
None
}
```
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