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Posted to reviews@spark.apache.org by "dtenedor (via GitHub)" <gi...@apache.org> on 2023/04/28 23:56:54 UTC
[GitHub] [spark] dtenedor commented on a diff in pull request #40615: [SPARK-16484][SQL] Add support for Datasketches HllSketch
dtenedor commented on code in PR #40615:
URL: https://github.com/apache/spark/pull/40615#discussion_r1180886403
##########
sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/expressions/aggregate/datasketchesAggregates.scala:
##########
@@ -0,0 +1,368 @@
+/*
+ * 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.expressions.aggregate
+
+import org.apache.datasketches.SketchesArgumentException
+import org.apache.datasketches.hll.{HllSketch, Union}
+import org.apache.datasketches.memory.Memory
+
+import org.apache.spark.sql.catalyst.InternalRow
+import org.apache.spark.sql.catalyst.expressions.{ExpectsInputTypes, Expression, ExpressionDescription, Literal}
+import org.apache.spark.sql.catalyst.trees.BinaryLike
+import org.apache.spark.sql.types.{AbstractDataType, BinaryType, BooleanType, DataType, IntegerType, LongType, StringType, TypeCollection}
+import org.apache.spark.unsafe.types.UTF8String
+
+
+/**
+ * The HllSketchAgg function utilizes a Datasketches HllSketch instance to
+ * probabilistically count the number of unique values in a given column, and
+ * outputs the binary representation of the HllSketch.
+ *
+ * See [[https://datasketches.apache.org/docs/HLL/HLL.html]] for more information
+ *
+ * @param child child expression against which unique counting will occur
+ * @param lgConfigK the log-base-2 of K, where K is the number of buckets or slots for the sketch
+ */
+// scalastyle:off line.size.limit
+@ExpressionDescription(
+ usage = """
+ _FUNC_(expr, lgConfigK) - Returns the HllSketch's updateable binary representation.
+ `lgConfigK` (optional) the log-base-2 of K, with K is the number of buckets or
+ slots for the HllSketch. """,
+ examples = """
+ Examples:
+ > SELECT hll_sketch_estimate(_FUNC_(col, 12)) FROM VALUES (1), (1), (2), (2), (3) tab(col);
+ 3
+ """,
+ group = "agg_funcs",
+ since = "3.5.0")
+// scalastyle:on line.size.limit
+case class HllSketchAgg(
+ child: Expression,
+ lgConfigKExpression: Expression,
+ mutableAggBufferOffset: Int = 0,
+ inputAggBufferOffset: Int = 0)
+ extends TypedImperativeAggregate[HllSketch] with BinaryLike[Expression] with ExpectsInputTypes {
+
+ // Hllsketch config - mark as lazy so that they're not evaluated during tree transformation.
+
+ lazy val lgConfigK: Int = {
+ val lgConfigK = lgConfigKExpression.eval().asInstanceOf[Int]
+ // can't use HllUtil.checkLgK so replicate the check
+ if (lgConfigK < 4 || lgConfigK > 21) {
+ throw new SketchesArgumentException("Invalid lgConfigK value")
+ } else {
Review Comment:
no need for `else` since you throw an exception above
##########
sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/expressions/aggregate/datasketchesAggregates.scala:
##########
@@ -0,0 +1,336 @@
+/*
+ * 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.expressions.aggregate
+
+
+import java.util.Locale
+
+import org.apache.datasketches.SketchesArgumentException
+import org.apache.datasketches.hll.{HllSketch, TgtHllType, Union}
+import org.apache.datasketches.memory.Memory
+
+import org.apache.spark.sql.catalyst.InternalRow
+import org.apache.spark.sql.catalyst.expressions.{ExpectsInputTypes, Expression, ExpressionDescription, Literal}
+import org.apache.spark.sql.catalyst.trees.{BinaryLike, TernaryLike}
+import org.apache.spark.sql.types.{AbstractDataType, AnyDataType, BinaryType, DataType, IntegerType, LongType, StringType}
+import org.apache.spark.unsafe.types.UTF8String
+
+
+/**
+ * The HllSketchAgg function utilizes a Datasketches HllSketch instance to
+ * probabilistically count the number of unique values in a given column, and
+ * outputs the binary representation of the HllSketch.
+ *
+ * See [[https://datasketches.apache.org/docs/HLL/HLL.html]] for more information
+ *
+ * @param child child expression against which unique counting will occur
+ * @param lgConfigK the log-base-2 of K, where K is the number of buckets or slots for the sketch
+ * @param tgtHllType the target type of the HllSketch to be used (HLL_4, HLL_6, HLL_8)
+ */
+@ExpressionDescription(
+ usage = """
+ _FUNC_(expr, lgConfigK, tgtHllType) - Returns the HllSketch's compact binary representation.
+ `lgConfigK` (optional) the log-base-2 of K, with K = the number of buckets for the HllSketch.
+ `tgtHllType` (optional) the target type of the HllSketch (HLL_4, HLL_6, HLL_8). """,
+ examples = """
+ Examples:
+ > SELECT hll_sketch_estimate(_FUNC_(col1, 12, 'HLL_4'))
+ FROM VALUES (1), (1), (2), (2), (3) tab(col1);
+ 3
+ """,
+ group = "agg_funcs",
+ since = "3.5.0")
+case class HllSketchAgg(
+ child: Expression,
+ lgConfigKExpression: Expression,
+ tgtHllTypeExpression: Expression,
+ mutableAggBufferOffset: Int = 0,
+ inputAggBufferOffset: Int = 0)
+ extends TypedImperativeAggregate[HllSketch] with TernaryLike[Expression] with ExpectsInputTypes {
+
+ // Hllsketch config - mark as lazy so that they're not evaluated during tree transformation.
+
+ lazy val lgConfigK: Int = second.eval().asInstanceOf[Int]
+ lazy val tgtHllType: TgtHllType = try {
+ TgtHllType.valueOf(third.eval().asInstanceOf[UTF8String].toString.toUpperCase(Locale.ROOT))
+ } catch {
+ case _: IllegalArgumentException =>
+ throw new SketchesArgumentException("Invalid tgtHllType value")
+ }
+
+ // Constructors
+
+ def this(child: Expression) = {
+ this(child, Literal(HllSketch.DEFAULT_LG_K), Literal(HllSketch.DEFAULT_HLL_TYPE.toString), 0, 0)
+ }
+
+ def this(child: Expression, lgConfigK: Expression) = {
+ this(child, lgConfigK, Literal(HllSketch.DEFAULT_HLL_TYPE.toString), 0, 0)
+ }
+
+ def this(child: Expression, lgConfigK: Int) = {
+ this(child, Literal(lgConfigK), Literal(HllSketch.DEFAULT_HLL_TYPE.toString), 0, 0)
+ }
+
+ def this(child: Expression, lgConfigK: Expression, tgtHllType: Expression) = {
+ this(child, lgConfigK, tgtHllType, 0, 0)
+ }
+
+ def this(child: Expression, lgConfigK: Int, tgtHllType: String) = {
+ this(child, Literal(lgConfigK), Literal(tgtHllType), 0, 0)
+ }
+
+ // Copy constructors required by ImperativeAggregate
+
+ override def withNewMutableAggBufferOffset(newMutableAggBufferOffset: Int): HllSketchAgg =
+ copy(mutableAggBufferOffset = newMutableAggBufferOffset)
+
+ override def withNewInputAggBufferOffset(newInputAggBufferOffset: Int): HllSketchAgg =
+ copy(inputAggBufferOffset = newInputAggBufferOffset)
+
+ override protected def withNewChildrenInternal(newFirst: Expression,
+ newSecond: Expression,
+ newThird: Expression): HllSketchAgg =
+ copy(child = newFirst, lgConfigKExpression = newSecond, tgtHllTypeExpression = newThird)
+
+ // Overrides for TernaryLike
+
+ override def first: Expression = child
+
+ override def second: Expression = lgConfigKExpression
+
+ override def third: Expression = tgtHllTypeExpression
+
+ // Overrides for TypedImperativeAggregate
+
+ override def prettyName: String = "hll_sketch_agg"
+
+ override def inputTypes: Seq[AbstractDataType] = Seq(AnyDataType, IntegerType, StringType)
+
+ override def dataType: DataType = BinaryType
+
+ override def nullable: Boolean = false
+
+ /**
+ * Instantiate an HllSketch instance using the lgConfigK and tgtHllType params.
+ *
+ * @return an HllSketch instance
+ */
+ override def createAggregationBuffer(): HllSketch = {
+ new HllSketch(lgConfigK, tgtHllType)
+ }
+
+ /**
+ * Evaluate the input row and update the HllSketch instance with the row's value.
+ * The update function only supports a subset of Spark SQL types, and an
+ * UnsupportedOperationException will be thrown for unsupported types.
+ *
+ * @param sketch The HllSketch instance.
+ * @param input an input row
+ */
+ override def update(sketch: HllSketch, input: InternalRow): HllSketch = {
+ val v = first.eval(input)
+ if (v != null) {
+ first.dataType match {
+ // Update implemented for a subset of types supported by HllSketch
+ // Spark SQL doesn't have equivalent types for ByteBuffer or char[] so leave those out
+ // Leaving out support for Array types, as unique counting these aren't a common use case
+ // Leaving out support for floating point types (IE DoubleType) due to imprecision
+ // TODO: implement support for decimal/datetime/interval types
+ case IntegerType => sketch.update(v.asInstanceOf[Int])
+ case LongType => sketch.update(v.asInstanceOf[Long])
+ case StringType => sketch.update(v.asInstanceOf[UTF8String].toString)
+ case BinaryType => sketch.update(v.asInstanceOf[Array[Byte]])
+ case dataType => throw new UnsupportedOperationException(
+ s"A HllSketch instance cannot be updates with a Spark ${dataType.toString} type")
+ }
+ }
+ sketch
+ }
+
+ /**
+ * Merges an input HllSketch into the sketch which is acting as the aggregation buffer.
+ *
+ * @param sketch the HllSketch instance used to store the aggregation result.
+ * @param input an input HllSketch instance
+ */
+ override def merge(sketch: HllSketch, input: HllSketch): HllSketch = {
+ val union = new Union(sketch.getLgConfigK)
+ union.update(sketch)
+ union.update(input)
+ union.getResult(sketch.getTgtHllType)
+ }
+
+ /**
+ * Returns an HllSketch derived from the input column or expression
+ *
+ * @param sketch HllSketch instance used as an aggregation buffer
+ * @return A binary sketch which can be evaluated or merged
+ */
+ override def eval(sketch: HllSketch): Any = {
+ sketch.toCompactByteArray
+ }
+
+ /** Convert the underlying HllSketch into an updatable byte array */
+ override def serialize(sketch: HllSketch): Array[Byte] = {
+ sketch.toUpdatableByteArray
+ }
+
+ /** De-serializes the updatable byte array into a HllSketch instance */
+ override def deserialize(buffer: Array[Byte]): HllSketch = {
+ HllSketch.heapify(buffer)
+ }
+}
+
+/**
+ * The HllUnionAgg function ingests and merges Datasketches HllSketch
+ * instances previously produced by the HllSketchBinary function, and
+ * outputs the merged HllSketch.
+ *
+ * See [[https://datasketches.apache.org/docs/HLL/HLL.html]] for more information
+ *
+ * @param child child expression against which unique counting will occur
+ * @param lgMaxK The largest maximum size for lgConfigK for the union operation.
Review Comment:
We could return an error in this case initially and defer the problem to the next PR if we want.
##########
sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/expressions/aggregate/datasketchesAggregates.scala:
##########
@@ -0,0 +1,368 @@
+/*
+ * 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.expressions.aggregate
+
+import org.apache.datasketches.SketchesArgumentException
+import org.apache.datasketches.hll.{HllSketch, Union}
+import org.apache.datasketches.memory.Memory
+
+import org.apache.spark.sql.catalyst.InternalRow
+import org.apache.spark.sql.catalyst.expressions.{ExpectsInputTypes, Expression, ExpressionDescription, Literal}
+import org.apache.spark.sql.catalyst.trees.BinaryLike
+import org.apache.spark.sql.types.{AbstractDataType, BinaryType, BooleanType, DataType, IntegerType, LongType, StringType, TypeCollection}
+import org.apache.spark.unsafe.types.UTF8String
+
+
+/**
+ * The HllSketchAgg function utilizes a Datasketches HllSketch instance to
+ * probabilistically count the number of unique values in a given column, and
+ * outputs the binary representation of the HllSketch.
+ *
+ * See [[https://datasketches.apache.org/docs/HLL/HLL.html]] for more information
+ *
+ * @param child child expression against which unique counting will occur
+ * @param lgConfigK the log-base-2 of K, where K is the number of buckets or slots for the sketch
+ */
+// scalastyle:off line.size.limit
+@ExpressionDescription(
+ usage = """
+ _FUNC_(expr, lgConfigK) - Returns the HllSketch's updateable binary representation.
+ `lgConfigK` (optional) the log-base-2 of K, with K is the number of buckets or
+ slots for the HllSketch. """,
+ examples = """
+ Examples:
+ > SELECT hll_sketch_estimate(_FUNC_(col, 12)) FROM VALUES (1), (1), (2), (2), (3) tab(col);
+ 3
+ """,
+ group = "agg_funcs",
+ since = "3.5.0")
+// scalastyle:on line.size.limit
+case class HllSketchAgg(
+ child: Expression,
+ lgConfigKExpression: Expression,
+ mutableAggBufferOffset: Int = 0,
+ inputAggBufferOffset: Int = 0)
+ extends TypedImperativeAggregate[HllSketch] with BinaryLike[Expression] with ExpectsInputTypes {
+
+ // Hllsketch config - mark as lazy so that they're not evaluated during tree transformation.
+
+ lazy val lgConfigK: Int = {
+ val lgConfigK = lgConfigKExpression.eval().asInstanceOf[Int]
+ // can't use HllUtil.checkLgK so replicate the check
+ if (lgConfigK < 4 || lgConfigK > 21) {
Review Comment:
can you move these magic numbers to private constants in the class with comments explaining what they mean?
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