Github user ron8hu commented on a diff in the pull request:
https://github.com/apache/spark/pull/16395#discussion_r95096602
--- Diff:
sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/plans/logical/estimation/FilterEstimation.scala
---
@@ -0,0 +1,479 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements. See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You under the Apache License, Version 2.0
+ * (the "License"); you may not use this file except in compliance with
+ * the License. You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.apache.spark.sql.catalyst.plans.logical.estimation
+
+import scala.collection.immutable.{HashSet, Map}
+import scala.collection.mutable
+
+import org.apache.spark.internal.Logging
+import org.apache.spark.sql.catalyst.expressions._
+import org.apache.spark.sql.catalyst.plans.logical._
+import org.apache.spark.sql.catalyst.util.DateTimeUtils
+import org.apache.spark.sql.types._
+import org.apache.spark.unsafe.types.UTF8String
+
+
+object FilterEstimation extends Logging {
+
+ /**
+ * We use a mutable colStats because we need to update the corresponding
ColumnStat
+ * for a column after we apply a predicate condition.
+ */
+ private var mutableColStats: mutable.Map[ExprId, ColumnStat] =
mutable.Map.empty
+
+ def estimate(plan: Filter): Option[Statistics] = {
+ val stats: Statistics = plan.child.statistics
+ if (stats.rowCount.isEmpty) return None
+
+ /** save a mutable copy of colStats so that we can later change it
recursively */
+ val statsExprIdMap: Map[ExprId, ColumnStat] =
+ stats.attributeStats.map(kv => (kv._1.exprId, kv._2))
+ mutableColStats = mutable.Map.empty ++= statsExprIdMap
+
+ /** save a copy of ExprId-to-Attribute map for later conversion use */
+ val expridToAttrMap: Map[ExprId, Attribute] =
+ stats.attributeStats.map(kv => (kv._1.exprId, kv._1))
+
+ /** estimate selectivity for this filter */
+ val percent: Double = calculateConditions(plan, plan.condition)
+
+ /** copy mutableColStats contents to an immutable AttributeMap */
+ val mutableAttributeStats: mutable.Map[Attribute, ColumnStat] =
+ mutableColStats.map(kv => (expridToAttrMap(kv._1) -> kv._2))
+ val newColStats = AttributeMap(mutableAttributeStats.toSeq)
+
+ val filteredRowCountValue: BigInt =
+ EstimationUtils.ceil(BigDecimal(stats.rowCount.get) * percent)
+ val avgRowSize = BigDecimal(EstimationUtils.getRowSize(plan.output,
newColStats))
+ val filteredSizeInBytes: BigInt =
+ EstimationUtils.ceil(BigDecimal(filteredRowCountValue) * avgRowSize)
+
+ Some(stats.copy(sizeInBytes = filteredSizeInBytes, rowCount =
Some(filteredRowCountValue),
+ attributeStats = newColStats))
+ }
+
+ def calculateConditions(
+ plan: Filter,
+ condition: Expression,
+ update: Boolean = true)
+ : Double = {
+ /**
+ * For conditions linked by And, we need to update stats after a
condition estimation
+ * so that the stats will be more accurate for subsequent estimation.
+ * For conditions linked by OR, we do not update stats after a
condition estimation.
+ */
+ condition match {
+ case And(cond1, cond2) =>
+ val p1 = calculateConditions(plan, cond1, update)
+ val p2 = calculateConditions(plan, cond2, update)
+ p1 * p2
+
+ case Or(cond1, cond2) =>
+ val p1 = calculateConditions(plan, cond1, update = false)
+ val p2 = calculateConditions(plan, cond2, update = false)
+ math.min(1.0, p1 + p2 - (p1 * p2))
+
+ case Not(cond) => calculateSingleCondition(plan, cond, isNot = true,
update = false)
+ case _ => calculateSingleCondition(plan, condition, isNot = false,
update)
+ }
+ }
+
+ def calculateSingleCondition(
+ plan: Filter,
+ condition: Expression,
+ isNot: Boolean,
+ update: Boolean)
+ : Double = {
+ var notSupported: Boolean = false
+ val percent: Double = condition match {
+ /**
+ * Currently we only support binary predicates where one side is a
column,
+ * and the other is a literal.
+ * Note that: all binary predicate computing methods assume the
literal is at the right side,
+ * so we will change the predicate order if not.
+ */
+ case op@LessThan(ExtractAttr(ar), l: Literal) =>
+ evaluateBinary(op, ar, l, update)
+ case op@LessThan(l: Literal, ExtractAttr(ar)) =>
+ evaluateBinary(GreaterThan(ar, l), ar, l, update)
+
+ case op@LessThanOrEqual(ExtractAttr(ar), l: Literal) =>
+ evaluateBinary(op, ar, l, update)
+ case op@LessThanOrEqual(l: Literal, ExtractAttr(ar)) =>
+ evaluateBinary(GreaterThanOrEqual(ar, l), ar, l, update)
+
+ case op@GreaterThan(ExtractAttr(ar), l: Literal) =>
+ evaluateBinary(op, ar, l, update)
+ case op@GreaterThan(l: Literal, ExtractAttr(ar)) =>
+ evaluateBinary(LessThan(ar, l), ar, l, update)
+
+ case op@GreaterThanOrEqual(ExtractAttr(ar), l: Literal) =>
+ evaluateBinary(op, ar, l, update)
+ case op@GreaterThanOrEqual(l: Literal, ExtractAttr(ar)) =>
+ evaluateBinary(LessThanOrEqual(ar, l), ar, l, update)
+
+ /** EqualTo does not care about the order */
+ case op@EqualTo(ExtractAttr(ar), l: Literal) =>
+ evaluateBinary(op, ar, l, update)
+ case op@EqualTo(l: Literal, ExtractAttr(ar)) =>
+ evaluateBinary(op, ar, l, update)
+
+ case In(ExtractAttr(ar), expList) if
!expList.exists(!_.isInstanceOf[Literal]) =>
+ /**
+ * Expression [In (value, seq[Literal])] will be replaced with
optimized version
+ * [InSet (value, HashSet[Literal])] in Optimizer, but only for
list.size > 10.
+ * Here we convert In into InSet anyway, because they share the
same processing logic.
+ */
+ val hSet = expList.map(e => e.eval())
+ evaluateInSet(ar, HashSet() ++ hSet, update)
+
+ case InSet(ExtractAttr(ar), set) =>
+ evaluateInSet(ar, set, update)
+
+ /**
+ * It's difficult to estimate IsNull after outer joins. Hence,
+ * we support IsNull and IsNotNull only when the child is a leaf
node (table).
+ */
+ case IsNull(ExtractAttr(ar)) =>
+ if (plan.child.isInstanceOf[LeafNode ]) {
+ evaluateIsNull(plan, ar, true, update)
+ }
+ else 1.0
+
+ case IsNotNull(ExtractAttr(ar)) =>
+ if (plan.child.isInstanceOf[LeafNode ]) {
+ evaluateIsNull(plan, ar, false, update)
+ }
+ else 1.0
+
+ case _ =>
+ /**
+ * TODO: it's difficult to support string operators without
advanced statistics.
+ * Hence, these string operators Like(_, _) | Contains(_, _) |
StartsWith(_, _)
+ * | EndsWith(_, _) are not supported yet
+ */
+ logDebug("[CBO] Unsupported filter condition: " + condition)
+ notSupported = true
+ 1.0
+ }
+ if (notSupported) {
+ 1.0
+ } else if (isNot) {
+ 1.0 - percent
+ } else {
+ percent
+ }
+ }
+
+ def evaluateIsNull(
+ plan: Filter,
+ attrRef: AttributeReference,
+ isNull: Boolean,
+ update: Boolean)
+ : Double = {
+ if (!mutableColStats.contains(attrRef.exprId)) {
+ logDebug("[CBO] No statistics for " + attrRef)
+ return 1.0
+ }
+ val aColStat = mutableColStats(attrRef.exprId)
+ val rowCountValue = plan.child.statistics.rowCount.get
+ val nullPercent: BigDecimal =
+ if (rowCountValue == 0) 0.0
+ else BigDecimal(aColStat.nullCount)/BigDecimal(rowCountValue)
+
+ if (update) {
+ val newStats =
+ if (isNull) aColStat.copy(distinctCount = 0, min = None, max =
None)
+ else aColStat.copy(nullCount = 0)
+
+ mutableColStats += (attrRef.exprId -> newStats)
+ }
+
+ val percent =
+ if (isNull) nullPercent.toDouble
+ else {
+ /** ISNOTNULL(column) */
+ 1.0 - nullPercent.toDouble
+ }
+
+ percent
+ }
+
+ /** This method evaluates binary comparison operators such as =, <, <=,
>, >= */
+ def evaluateBinary(
+ op: BinaryComparison,
+ attrRef: AttributeReference,
+ literal: Literal,
+ update: Boolean)
+ : Double = {
+ if (!mutableColStats.contains(attrRef.exprId)) {
+ logDebug("[CBO] No statistics for " + attrRef)
+ return 1.0
+ }
+
+ /** Make sure that the Date/Timestamp literal is a valid one */
+ attrRef.dataType match {
+ case DateType =>
+ val dateLiteral =
DateTimeUtils.stringToDate(literal.value.asInstanceOf[UTF8String])
+ if (dateLiteral.isEmpty) {
+ logDebug("[CBO] Date literal is wrong, No statistics for " +
attrRef)
+ return 1.0
+ }
+ case TimestampType =>
+ val tsLiteral =
DateTimeUtils.stringToTimestamp(literal.value.asInstanceOf[UTF8String])
+ if (tsLiteral.isEmpty) {
+ logDebug("[CBO] Timestamp literal is wrong, No statistics for "
+ attrRef)
+ return 1.0
+ }
+ case _ =>
+ }
+
+ op match {
+ case EqualTo(l, r) => evaluateEqualTo(op, attrRef, literal, update)
+ case _ =>
+ attrRef.dataType match {
+ case _: NumericType | DateType | TimestampType =>
+ evaluateBinaryForNumeric(op, attrRef, literal, update)
+ case StringType | BinaryType =>
+ /**
+ * TODO: It is difficult to support other binary comparisons
for String/Binary
+ * type without min/max and advanced statistics like histogram.
+ */
+ logDebug("[CBO] No statistics for String/Binary type " +
attrRef)
+ return 1.0
+ }
+ }
+ }
+
+ /**
+ * This method converts a numeric or Literal value of numeric type to a
BigDecimal value.
+ * If isNumeric is true, then it is a numeric value. Otherwise, it is a
Literal value.
+ */
+ def numericLiteralToBigDecimal(
+ literal: Any,
+ dataType: DataType,
+ isNumeric: Boolean = false)
+ : BigDecimal = {
+ dataType match {
+ case _: IntegralType =>
+ if (isNumeric) BigDecimal(literal.asInstanceOf[Long])
+ else
BigDecimal(literal.asInstanceOf[Literal].value.asInstanceOf[Long])
+ case _: FractionalType =>
+ if (isNumeric) BigDecimal(literal.asInstanceOf[Double])
+ else
BigDecimal(literal.asInstanceOf[Literal].value.asInstanceOf[Double])
+ case DateType =>
+ if (isNumeric) BigDecimal(literal.asInstanceOf[BigInt])
+ else {
+ val dateLiteral = DateTimeUtils.stringToDate(
+ literal.asInstanceOf[Literal].value.asInstanceOf[UTF8String])
+ BigDecimal(dateLiteral.asInstanceOf[BigInt])
+ }
+ case TimestampType =>
+ if (isNumeric) BigDecimal(literal.asInstanceOf[BigInt])
+ else {
+ val tsLiteral = DateTimeUtils.stringToTimestamp(
+ literal.asInstanceOf[Literal].value.asInstanceOf[UTF8String])
+ BigDecimal(tsLiteral.asInstanceOf[BigInt])
+ }
+ }
+ }
+
+ /** This method evaluates the equality predicate for all data types. */
+ def evaluateEqualTo(
+ op: BinaryComparison,
+ attrRef: AttributeReference,
+ literal: Literal,
+ update: Boolean)
+ : Double = {
+
+ val aColStat = mutableColStats(attrRef.exprId)
+ val ndv = aColStat.distinctCount
+
+ /**
+ * decide if the value is in [min, max] of the column.
+ * We currently don't store min/max for binary/string type.
+ * Hence, we assume it is in boundary for binary/string type.
+ */
+ val inBoundary: Boolean = attrRef.dataType match {
+ case _: NumericType | DateType | TimestampType =>
+ val statsRange =
+ Range(aColStat.min, aColStat.max,
attrRef.dataType).asInstanceOf[NumericRange]
+ val lit = numericLiteralToBigDecimal(literal, attrRef.dataType)
+ (lit >= statsRange.min) && (lit <= statsRange.max)
+
+ case _ => true /** for String/Binary type */
+ }
+
+ val percent: Double =
+ if (inBoundary) {
+
+ if (update) {
+ /**
+ * We update ColumnStat structure after apply this equality
predicate.
+ * Set distinctCount to 1. Set nullCount to 0.
+ */
+ val newStats = attrRef.dataType match {
+ case _: NumericType | DateType | TimestampType =>
+ val newValue = Some(literal.value)
+ aColStat.copy(distinctCount = 1, min = newValue,
+ max = newValue, nullCount = 0)
+ case _ => aColStat.copy(distinctCount = 1, nullCount = 0)
+ }
+ mutableColStats += (attrRef.exprId -> newStats)
+ }
+
+ 1.0 / ndv.toDouble
+ } else {
+ 0.0
+ }
+
+ percent
+ }
+
+ def evaluateInSet(
--- End diff --
Yes, the return value is a double value showing the percentage of rows
meeting a given condition. Also I will add comments for this method in JavaDoc
style.
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