suneet-amp commented on a change in pull request #8814: SQL: Add RAND() function. URL: https://github.com/apache/incubator-druid/pull/8814#discussion_r342201369
########## File path: processing/src/main/java/org/apache/druid/query/expression/RandExprMacro.java ########## @@ -0,0 +1,95 @@ +/* + * 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.druid.query.expression; + +import com.google.common.collect.Iterables; +import org.apache.druid.java.util.common.IAE; +import org.apache.druid.math.expr.Expr; +import org.apache.druid.math.expr.ExprEval; +import org.apache.druid.math.expr.ExprMacroTable; +import org.apache.druid.segment.DimensionHandlerUtils; + +import java.util.Collections; +import java.util.List; +import java.util.Random; +import java.util.concurrent.ThreadLocalRandom; +import java.util.function.DoubleSupplier; + +public class RandExprMacro implements ExprMacroTable.ExprMacro +{ + @Override + public String name() + { + return "rand"; + } + + @Override + public Expr apply(List<Expr> args) + { + final DoubleSupplier randomGenerator; + + if (args.isEmpty()) { + randomGenerator = () -> ThreadLocalRandom.current().nextDouble(); + } else if (args.size() == 1) { + final Expr seedArg = Iterables.getOnlyElement(args); + if (seedArg.isLiteral()) { + final Long seedValue = DimensionHandlerUtils.convertObjectToLong(seedArg.getLiteralValue()); + if (seedValue != null) { + final Random random = new Random(seedValue); + randomGenerator = random::nextDouble; + } else { + throw new IAE("Function[%s] first argument must be a number literal"); + } + } else { + throw new IAE("Function[%s] first argument must be a number literal"); + } + } else { + throw new IAE("Function[%s] needs zero or one arguments", name()); + } + + class RandExpr extends ExprMacroTable.BaseScalarMacroFunctionExpr Review comment: 👀 I've never seen this pattern before. dumb guy question: Is there any advantage of using this vs a private static inner class. Do we do this just so we don't have to pass `randomGenerator` to the constructor of this class? ---------------------------------------------------------------- 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 --------------------------------------------------------------------- To unsubscribe, e-mail: [email protected] For additional commands, e-mail: [email protected]
