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[SPARK-49000][SQL][3.5] Fix "select count(distinct 1) from t" where t is empty table by expanding RewriteDistinctAggregates #47566

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[SPARK-49000][SQL][3.5] Fix "select count(distinct 1) from t" where t is empty table by expanding RewriteDistinctAggregates #47566

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uros-db Aug 1, 2024
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Remove collation
uros-db Aug 1, 2024
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uros-db Aug 1, 2024
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16 changes: 13 additions & 3 deletions ...st/src/main/scala/org/apache/spark/sql/catalyst/optimizer/RewriteDistinctAggregates.scala
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Original file line number Diff line number Diff line change
Expand Up @@ -197,15 +197,25 @@ import org.apache.spark.util.collection.Utils
* techniques.
*/
object RewriteDistinctAggregates extends Rule[LogicalPlan] {
private def mustRewrite(
distinctAggs: Seq[AggregateExpression],
groupingExpressions: Seq[Expression]): Boolean = {
// If there are any distinct AggregateExpressions with filter, we need to rewrite the query.
// Also, if there are no grouping expressions and all distinct aggregate expressions are
// foldable, we need to rewrite the query, e.g. SELECT COUNT(DISTINCT 1). Without this case,
// non-grouping aggregation queries with distinct aggregate expressions will be incorrectly
// handled by the aggregation strategy, causing wrong results when working with empty tables.
distinctAggs.exists(_.filter.isDefined) || (groupingExpressions.isEmpty &&
distinctAggs.exists(_.aggregateFunction.children.forall(_.foldable)))
}

private def mayNeedtoRewrite(a: Aggregate): Boolean = {
val aggExpressions = collectAggregateExprs(a)
val distinctAggs = aggExpressions.filter(_.isDistinct)
// We need at least two distinct aggregates or the single distinct aggregate group exists filter
// clause for this rule because aggregation strategy can handle a single distinct aggregate
// group without filter clause.
// This check can produce false-positives, e.g., SUM(DISTINCT a) & COUNT(DISTINCT a).
distinctAggs.size > 1 || distinctAggs.exists(_.filter.isDefined)
distinctAggs.size > 1 || mustRewrite(distinctAggs, a.groupingExpressions)
}

def apply(plan: LogicalPlan): LogicalPlan = plan.transformUpWithPruning(
Expand Down Expand Up @@ -236,7 +246,7 @@ object RewriteDistinctAggregates extends Rule[LogicalPlan] {
}

// Aggregation strategy can handle queries with a single distinct group without filter clause.
if (distinctAggGroups.size > 1 || distinctAggs.exists(_.filter.isDefined)) {
if (distinctAggGroups.size > 1 || mustRewrite(distinctAggs, a.groupingExpressions)) {
// Create the attributes for the grouping id and the group by clause.
val gid = AttributeReference("gid", IntegerType, nullable = false)()
val groupByMap = a.groupingExpressions.collect {
Expand Down
111 changes: 111 additions & 0 deletions sql/core/src/test/scala/org/apache/spark/sql/DataFrameAggregateSuite.scala
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Expand Up @@ -24,6 +24,7 @@ import scala.util.Random
import org.scalatest.matchers.must.Matchers.the

import org.apache.spark.{SparkException, SparkThrowable}
import org.apache.spark.sql.catalyst.plans.logical.Expand
import org.apache.spark.sql.execution.WholeStageCodegenExec
import org.apache.spark.sql.execution.adaptive.AdaptiveSparkPlanHelper
import org.apache.spark.sql.execution.aggregate.{HashAggregateExec, ObjectHashAggregateExec, SortAggregateExec}
Expand Down Expand Up @@ -2150,6 +2151,116 @@ class DataFrameAggregateSuite extends QueryTest
checkAnswer(df, Row(1, 2, 2) :: Row(3, 1, 1) :: Nil)
}
}

test("aggregating with various distinct expressions") {
abstract class AggregateTestCaseBase(
val query: String,
val resultSeq: Seq[Seq[Row]],
val hasExpandNodeInPlan: Boolean)
case class AggregateTestCase(
override val query: String,
override val resultSeq: Seq[Seq[Row]],
override val hasExpandNodeInPlan: Boolean)
extends AggregateTestCaseBase(query, resultSeq, hasExpandNodeInPlan)
case class AggregateTestCaseDefault(
override val query: String)
extends AggregateTestCaseBase(
query,
Seq(Seq(Row(0)), Seq(Row(1)), Seq(Row(1))),
hasExpandNodeInPlan = true)

val t = "t"
val testCases: Seq[AggregateTestCaseBase] = Seq(
AggregateTestCaseDefault(
s"""SELECT COUNT(DISTINCT "col") FROM $t"""
),
AggregateTestCaseDefault(
s"SELECT COUNT(DISTINCT 1) FROM $t"
),
AggregateTestCaseDefault(
s"SELECT COUNT(DISTINCT 1 + 2) FROM $t"
),
AggregateTestCaseDefault(
s"SELECT COUNT(DISTINCT 1, 2, 1 + 2) FROM $t"
),
AggregateTestCase(
s"SELECT COUNT(1), COUNT(DISTINCT 1) FROM $t",
Seq(Seq(Row(0, 0)), Seq(Row(1, 1)), Seq(Row(2, 1))),
hasExpandNodeInPlan = true
),
AggregateTestCaseDefault(
s"""SELECT COUNT(DISTINCT 1, "col") FROM $t"""
),
AggregateTestCaseDefault(
s"""SELECT COUNT(DISTINCT current_date()) FROM $t"""
),
AggregateTestCaseDefault(
s"""SELECT COUNT(DISTINCT array(1, 2)[1]) FROM $t"""
),
AggregateTestCaseDefault(
s"""SELECT COUNT(DISTINCT map(1, 2)[1]) FROM $t"""
),
AggregateTestCaseDefault(
s"""SELECT COUNT(DISTINCT struct(1, 2).col1) FROM $t"""
),
AggregateTestCase(
s"SELECT COUNT(DISTINCT 1) FROM $t GROUP BY col",
Seq(Seq(), Seq(Row(1)), Seq(Row(1), Row(1))),
hasExpandNodeInPlan = false
),
AggregateTestCaseDefault(
s"SELECT COUNT(DISTINCT 1) FROM $t WHERE 1 = 1"
),
AggregateTestCase(
s"SELECT COUNT(DISTINCT 1) FROM $t WHERE 1 = 0",
Seq(Seq(Row(0)), Seq(Row(0)), Seq(Row(0))),
hasExpandNodeInPlan = false
),
AggregateTestCase(
s"SELECT SUM(DISTINCT 1) FROM (SELECT COUNT(DISTINCT 1) FROM $t)",
Seq(Seq(Row(1)), Seq(Row(1)), Seq(Row(1))),
hasExpandNodeInPlan = false
),
AggregateTestCase(
s"SELECT SUM(DISTINCT 1) FROM (SELECT COUNT(1) FROM $t)",
Seq(Seq(Row(1)), Seq(Row(1)), Seq(Row(1))),
hasExpandNodeInPlan = false
),
AggregateTestCase(
s"SELECT SUM(1) FROM (SELECT COUNT(DISTINCT 1) FROM $t)",
Seq(Seq(Row(1)), Seq(Row(1)), Seq(Row(1))),
hasExpandNodeInPlan = false
),
AggregateTestCaseDefault(
s"SELECT SUM(x) FROM (SELECT COUNT(DISTINCT 1) AS x FROM $t)"),
AggregateTestCase(
s"""SELECT COUNT(DISTINCT 1), COUNT(DISTINCT "col") FROM $t""",
Seq(Seq(Row(0, 0)), Seq(Row(1, 1)), Seq(Row(1, 1))),
hasExpandNodeInPlan = true
),
AggregateTestCase(
s"""SELECT COUNT(DISTINCT 1), COUNT(DISTINCT col) FROM $t""",
Seq(Seq(Row(0, 0)), Seq(Row(1, 1)), Seq(Row(1, 2))),
hasExpandNodeInPlan = true
)
)
withTable(t) {
sql(s"create table $t(col int) using parquet")
Seq(0, 1, 2).foreach(columnValue => {
if (columnValue != 0) {
sql(s"insert into $t(col) values($columnValue)")
}
testCases.foreach(testCase => {
val query = sql(testCase.query)
checkAnswer(query, testCase.resultSeq(columnValue))
val hasExpandNodeInPlan = query.queryExecution.optimizedPlan.collectFirst {
case _: Expand => true
}.nonEmpty
assert(hasExpandNodeInPlan == testCase.hasExpandNodeInPlan)
})
})
}
}
}

case class B(c: Option[Double])
Expand Down