JingsongLi commented on a change in pull request #8019: [FLINK-11981][table-planner-blink] Introduce ProjectionCodeGenerator and HashCodeGenerator for BaseRow URL: https://github.com/apache/flink/pull/8019#discussion_r268496544
########## File path: flink-table/flink-table-planner-blink/src/main/scala/org/apache/flink/table/codegen/HashCodeGenerator.scala ########## @@ -0,0 +1,129 @@ +/* + * 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.flink.table.codegen + +import org.apache.flink.table.`type`.{ArrayType, DateType, DecimalType, InternalType, InternalTypes, TimestampType} +import org.apache.flink.table.codegen.CodeGenUtils.{BASE_ROW, newName} +import org.apache.flink.table.codegen.Indenter.toISC +import org.apache.flink.table.dataformat.BaseRow +import org.apache.flink.table.dataformat.util.HashUtil +import org.apache.flink.table.generated.{GeneratedHashFunction, HashFunction} +import org.apache.flink.util.MathUtils + +/** + * CodeGenerator for hash code [[BaseRow]], Calculate a hash value based on some fields + * of [[BaseRow]]. + * NOTE: If you need a hash value that is more evenly distributed, call [[MathUtils.murmurHash]] + * outside to scatter. + */ +object HashCodeGenerator { + + /** + * A sequence of prime numbers to be used for salting the computed hash values. + * Based on some empirical evidence, we are using a 32-element subsequence of the + * OEIS sequence #A068652 (numbers such that every cyclic permutation is a prime). + * + * @see <a href="http://en.wikipedia.org/wiki/List_of_prime_numbers";> + * http://en.wikipedia.org/wiki/List_of_prime_numbers</a> + * @see <a href="http://oeis.org/A068652";>http://oeis.org/A068652</a> + */ + val HASH_SALT: Array[Int] = Array[Int]( + 73, 79, 97, 113, 131, 197, 199, 311, 337, 373, 719, 733, 919, 971, 991, 1193, 1931, 3119, + 3779, 7793, 7937, 9311, 9377, 11939, 19391, 19937, 37199, 39119, 71993, 91193, 93719, 93911) + + def generateRowHash( + ctx: CodeGeneratorContext, + input: InternalType, + name: String, + hashFields: Array[Int]): GeneratedHashFunction = { + val className = newName(name) + val baseClass = classOf[HashFunction] + val inputTerm = CodeGenUtils.DEFAULT_INPUT1_TERM + + val accessExprs = hashFields.map( + idx => GenerateUtils.generateFieldAccess(ctx, input, inputTerm, idx)) + + val (hashBody, resultTerm) = generateCodeBody(accessExprs) + val code = + j""" + public class $className implements ${baseClass.getCanonicalName} { + + ${ctx.reuseMemberCode()} + + public $className(Object[] references) throws Exception { + ${ctx.reuseInitCode()} + } + + @Override + public int hashCode($BASE_ROW $inputTerm) { + ${ctx.reuseLocalVariableCode()} + $hashBody + return $resultTerm; + } + } + """.stripMargin + + new GeneratedHashFunction(className, code, ctx.references.toArray) + } + + private def generateCodeBody(accessExprs: Seq[GeneratedExpression]): (String, String) = { + val hashIntTerm = CodeGenUtils.newName("hashCode") + var i = -1 + val hashBodyCode = accessExprs.map((expr) => { + i = i + 1 + s""" + |$hashIntTerm *= ${HASH_SALT(i & 0x1F)}; + |${expr.code} + |if (!${expr.nullTerm}) { + | $hashIntTerm += ${hashExpr(expr)}; + |} + |""".stripMargin + + }).mkString("\n") + (s""" + |int $hashIntTerm = 0; + |$hashBodyCode""".stripMargin, hashIntTerm) + } + + private def hashExpr(expr: GeneratedExpression): String = { + val util = classOf[HashUtil].getCanonicalName + s"$util.hash${hashNameInBinaryUtil(expr.resultType)}(${expr.resultTerm})" + } + + private def hashNameInBinaryUtil(t: InternalType): String = t match { Review comment: done ---------------------------------------------------------------- This is an automated message from the Apache Git Service. To respond to the message, please log on to GitHub and use the URL above to go to the specific comment. For queries about this service, please contact Infrastructure at: [email protected] With regards, Apache Git Services
