[SPARK-38836][SQL] Improve the performance of ExpressionSet #36121
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,168 @@ | ||
| /* | ||
| * 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. | ||
| */ | ||
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| package org.apache.spark.sql.catalyst.expressions | ||
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| import scala.collection.{mutable, IterableFactory, IterableOps} | ||
| import scala.collection.mutable.ArrayBuffer | ||
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| object ExpressionSet { | ||
| /** Constructs a new [[ExpressionSet]] by applying [[Canonicalize]] to `expressions`. */ | ||
| def apply(expressions: IterableOnce[Expression]): ExpressionSet = { | ||
| val set = new ExpressionSet() | ||
| expressions.iterator.foreach(set.add) | ||
| set | ||
| } | ||
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| def apply(): ExpressionSet = { | ||
| new ExpressionSet() | ||
| } | ||
| } | ||
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| /** | ||
| * A [[Set]] where membership is determined based on determinacy and a canonical representation of | ||
| * an [[Expression]] (i.e. one that attempts to ignore cosmetic differences). | ||
| * See [[Canonicalize]] for more details. | ||
| * | ||
| * Internally this set uses the canonical representation, but keeps also track of the original | ||
| * expressions to ease debugging. Since different expressions can share the same canonical | ||
| * representation, this means that operations that extract expressions from this set are only | ||
| * guaranteed to see at least one such expression. For example: | ||
| * | ||
| * {{{ | ||
| * val set = ExpressionSet(a + 1, 1 + a) | ||
| * | ||
| * set.iterator => Iterator(a + 1) | ||
| * set.contains(a + 1) => true | ||
| * set.contains(1 + a) => true | ||
| * set.contains(a + 2) => false | ||
| * }}} | ||
| * | ||
| * For non-deterministic expressions, they are always considered as not contained in the [[Set]]. | ||
| * On adding a non-deterministic expression, simply append it to the original expressions. | ||
| * This is consistent with how we define `semanticEquals` between two expressions. | ||
| * | ||
| * The constructor of this class is protected so caller can only initialize an Expression from | ||
| * empty, then build it using `add` and `remove` methods. So every instance of this class holds the | ||
| * invariant that: | ||
| * 1. Every expr `e` in `baseSet` satisfies `e.deterministic && e.canonicalized == e` | ||
| * 2. Every deterministic expr `e` in `originals` satisfies that `e.canonicalized` is already | ||
| * accessed. | ||
| */ | ||
| class ExpressionSet protected( | ||
| private val baseSet: mutable.Set[Expression] = new mutable.HashSet, | ||
| private var originals: mutable.Buffer[Expression] = new ArrayBuffer) | ||
| extends scala.collection.Set[Expression] | ||
| with scala.collection.SetOps[Expression, scala.collection.Set, ExpressionSet] { | ||
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| override protected def fromSpecific(coll: IterableOnce[Expression]): ExpressionSet = { | ||
| val set = new ExpressionSet() | ||
| coll.iterator.foreach(set.add) | ||
| set | ||
| } | ||
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| override protected def newSpecificBuilder: mutable.Builder[Expression, ExpressionSet] = | ||
| new mutable.Builder[Expression, ExpressionSet] { | ||
| var expr_set: ExpressionSet = new ExpressionSet() | ||
| def clear(): Unit = expr_set = new ExpressionSet() | ||
| def result(): ExpressionSet = expr_set | ||
| def addOne(expr: Expression): this.type = { | ||
| expr_set.add(expr) | ||
| this | ||
| } | ||
| } | ||
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| override def empty: ExpressionSet = new ExpressionSet() | ||
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| override def diff(that: scala.collection.Set[Expression]): ExpressionSet = this -- that | ||
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| protected def add(e: Expression): Unit = { | ||
| if (!e.deterministic) { | ||
| originals += e | ||
| } else if (!baseSet.contains(e.canonicalized)) { | ||
| baseSet.add(e.canonicalized) | ||
| originals += e | ||
| } | ||
| } | ||
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| protected def remove(e: Expression): Unit = { | ||
| if (e.deterministic) { | ||
| baseSet.remove(e.canonicalized) | ||
| originals = originals.filter(!_.semanticEquals(e)) | ||
| } | ||
| } | ||
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| override def contains(elem: Expression): Boolean = baseSet.contains(elem.canonicalized) | ||
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| override def filter(p: Expression => Boolean): ExpressionSet = { | ||
| val newBaseSet = baseSet.filter(e => p(e)) | ||
| val newOriginals = originals.filter(e => p(e.canonicalized)) | ||
| new ExpressionSet(newBaseSet, newOriginals) | ||
| } | ||
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| override def filterNot(p: Expression => Boolean): ExpressionSet = { | ||
| val newBaseSet = baseSet.filterNot(e => p(e)) | ||
| val newOriginals = originals.filterNot(e => p(e.canonicalized)) | ||
| new ExpressionSet(newBaseSet, newOriginals) | ||
| } | ||
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| override def +(elem: Expression): ExpressionSet = { | ||
| val newSet = clone() | ||
| newSet.add(elem) | ||
| newSet | ||
| } | ||
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| override def -(elem: Expression): ExpressionSet = { | ||
| val newSet = clone() | ||
| newSet.remove(elem) | ||
| newSet | ||
| } | ||
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| def map(f: Expression => Expression): ExpressionSet = { | ||
| val newSet = new ExpressionSet() | ||
| this.iterator.foreach(elem => newSet.add(f(elem))) | ||
| newSet | ||
| } | ||
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| def flatMap(f: Expression => Iterable[Expression]): ExpressionSet = { | ||
| val newSet = new ExpressionSet() | ||
| this.iterator.foreach(f(_).foreach(newSet.add)) | ||
| newSet | ||
| } | ||
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| override def iterator: Iterator[Expression] = originals.iterator | ||
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| override def equals(obj: Any): Boolean = obj match { | ||
| case other: ExpressionSet => this.baseSet == other.baseSet | ||
| case _ => false | ||
| } | ||
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| override def hashCode(): Int = baseSet.hashCode() | ||
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| override def clone(): ExpressionSet = new ExpressionSet(baseSet.clone(), originals.clone()) | ||
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| /** | ||
| * Returns a string containing both the post [[Canonicalize]] expressions and the original | ||
| * expressions in this set. | ||
| */ | ||
| def toDebugString: String = | ||
| s""" | ||
| |baseSet: ${baseSet.mkString(", ")} | ||
| |originals: ${originals.mkString(", ")} | ||
| """.stripMargin | ||
| } | ||
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There are two changes happening in this line.
originals = originals.filter(...). This is O(n) as the previous implementation is O(mn).semanticEqualsinstead of the previous_.canonicalized == e.canonicalizedas the condition.semanticEqualscan short circuit and avoid unnecessary access ofcanonicalizedfor non-deterministic expressions.By invariant 2, the current implementation should not evaluate
canonicalizedat all.