Github user ron8hu commented on a diff in the pull request:
https://github.com/apache/spark/pull/17148#discussion_r104557294
--- Diff:
sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/plans/logical/statsEstimation/FilterEstimation.scala
---
@@ -90,32 +95,43 @@ case class FilterEstimation(plan: Filter, catalystConf:
CatalystConf) extends Lo
def calculateFilterSelectivity(condition: Expression, update: Boolean =
true): Option[Double] = {
condition match {
case And(cond1, cond2) =>
- // For ease of debugging, we compute percent1 and percent2 in 2
statements.
- val percent1 = calculateFilterSelectivity(cond1, update)
- val percent2 = calculateFilterSelectivity(cond2, update)
- (percent1, percent2) match {
- case (Some(p1), Some(p2)) => Some(p1 * p2)
- case (Some(p1), None) => Some(p1)
- case (None, Some(p2)) => Some(p2)
- case (None, None) => None
- }
+ val percent1 = calculateFilterSelectivity(cond1,
update).getOrElse(1.0)
+ val percent2 = calculateFilterSelectivity(cond2,
update).getOrElse(1.0)
+ Some(percent1 * percent2)
case Or(cond1, cond2) =>
- // For ease of debugging, we compute percent1 and percent2 in 2
statements.
- val percent1 = calculateFilterSelectivity(cond1, update = false)
- val percent2 = calculateFilterSelectivity(cond2, update = false)
- (percent1, percent2) match {
- case (Some(p1), Some(p2)) => Some(math.min(1.0, p1 + p2 - (p1 *
p2)))
- case (Some(p1), None) => Some(1.0)
- case (None, Some(p2)) => Some(1.0)
- case (None, None) => None
+ val percent1 = calculateFilterSelectivity(cond1, update =
false).getOrElse(1.0)
+ val percent2 = calculateFilterSelectivity(cond2, update =
false).getOrElse(1.0)
+ Some(percent1 + percent2 - (percent1 * percent2))
+
+ // For AND and OR conditions, we will estimate conservatively if one
of two
+ // components is not supported, e.g. suppose c1 is not supported,
+ // then p(And(c1, c2)) = p(c2), and p(Or(c1, c2)) = 1.0.
+ // But once they are wrapped in NOT condition, then after 1 - p, it
becomes
+ // under-estimation. So in these cases, we consider them as
unsupported.
+ case Not(And(cond1, cond2)) =>
+ val p1 = calculateFilterSelectivity(cond1, update = false)
+ val p2 = calculateFilterSelectivity(cond2, update = false)
+ if (p1.isDefined && p2.isDefined) {
+ Some(1 - p1.get * p2.get)
+ } else {
+ None
}
- case Not(cond) => calculateFilterSelectivity(cond, update = false)
match {
- case Some(percent) => Some(1.0 - percent)
- // for not-supported condition, set filter selectivity to a
conservative estimate 100%
- case None => None
- }
+ case Not(Or(cond1, cond2)) =>
+ val p1 = calculateFilterSelectivity(cond1, update = false)
+ val p2 = calculateFilterSelectivity(cond2, update = false)
+ if (p1.isDefined && p2.isDefined) {
+ Some(1 - (p1.get + p2.get - (p1.get * p2.get)))
+ } else {
+ None
--- End diff --
This is good. We compute selectivity for "Not(Or(cond1, cond2))" only
when we can get selectivity for both conditions. If we cannot get selectivity
for either one or both, then we just return None. It is a clean solution.
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