| /* |
| * 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.phoenix.expression.function; |
| |
| import java.io.DataInput; |
| import java.io.IOException; |
| import java.util.List; |
| import java.util.Random; |
| |
| import org.apache.hadoop.hbase.io.ImmutableBytesWritable; |
| import org.apache.phoenix.expression.Determinism; |
| import org.apache.phoenix.expression.Expression; |
| import org.apache.phoenix.expression.LiteralExpression; |
| import org.apache.phoenix.parse.FunctionParseNode.Argument; |
| import org.apache.phoenix.parse.FunctionParseNode.BuiltInFunction; |
| import org.apache.phoenix.schema.tuple.Tuple; |
| import org.apache.phoenix.schema.types.PDataType; |
| import org.apache.phoenix.schema.types.PDouble; |
| import org.apache.phoenix.schema.types.PLong; |
| |
| /** |
| * Random function that produces a unique value upon each invocation unless a seed is provided. |
| * If a seed is provided the returned value is identical across each invocation for a single row, but different across multiple rows. |
| * The seed must be a constant. |
| * <p> |
| * Example: |
| * <pre> |
| * {@code |
| * 0: jdbc:phoenix:localhost> select rand(), rand(), rand(1), rand(2), rand(1) from t; |
| * +----------------------------+----------------------------+----------------------------+----------------------------+-----------------------+ |
| * | RAND() | RAND() | RAND(1) | RAND(2) | RAND(1) | |
| * +----------------------------+----------------------------+----------------------------+----------------------------+-----------------------+ |
| * | 0.18927325291276054 | 0.19335253869230284 | 0.7308781907032909 | 0.7311469360199058 | 0.7308781907032909 | |
| * | 0.08156917775368278 | 0.10178318739559034 | 0.41008081149220166 | 0.9014476240300544 | 0.41008081149220166 | |
| * +----------------------------+----------------------------+----------------------------+----------------------------+-----------------------+ |
| * 2 rows selected (0.096 seconds) |
| * 0: jdbc:phoenix:localhost> select rand(), rand(), rand(1), rand(2), rand(1) from t; |
| * +----------------------------+----------------------------+----------------------------+----------------------------+-----------------------+ |
| * | RAND() | RAND() | RAND(1) | RAND(2) | RAND(1) | |
| * +----------------------------+----------------------------+----------------------------+----------------------------+-----------------------+ |
| * | 0.6452639556507597 | 0.8167638693890659 | 0.7308781907032909 | 0.7311469360199058 | 0.7308781907032909 | |
| * | 0.8084646053276106 | 0.6969504742211767 | 0.41008081149220166 | 0.9014476240300544 | 0.41008081149220166 | |
| * +----------------------------+----------------------------+----------------------------+----------------------------+-----------------------+ |
| * 2 rows selected (0.098 seconds) |
| * } |
| * </pre> |
| */ |
| @BuiltInFunction(name = RandomFunction.NAME, args = {@Argument(allowedTypes={PLong.class},defaultValue="null",isConstant=true)}) |
| public class RandomFunction extends ScalarFunction { |
| public static final String NAME = "RAND"; |
| private Random random; |
| private boolean hasSeed; |
| private Double current; |
| |
| public RandomFunction() { |
| } |
| |
| public RandomFunction(List<Expression> children) { |
| super(children); |
| init(); |
| } |
| |
| private void init() { |
| Number seed = (Number)((LiteralExpression)children.get(0)).getValue(); |
| random = seed == null ? new Random() : new Random(seed.longValue()); |
| hasSeed = seed != null; |
| current = null; |
| } |
| |
| @Override |
| public void readFields(DataInput input) throws IOException { |
| super.readFields(input); |
| init(); |
| } |
| |
| @Override |
| public boolean evaluate(Tuple tuple, ImmutableBytesWritable ptr) { |
| if (current == null) { |
| current = random.nextDouble(); |
| } |
| ptr.set(PDouble.INSTANCE.toBytes(current)); |
| return true; |
| } |
| |
| // produce a new random value for each row |
| @Override |
| public void reset() { |
| super.reset(); |
| current = null; |
| } |
| |
| @Override |
| public PDataType<?> getDataType() { |
| return PDouble.INSTANCE; |
| } |
| |
| @Override |
| public String getName() { |
| return NAME; |
| } |
| |
| @Override |
| public Determinism getDeterminism() { |
| return hasSeed ? Determinism.PER_ROW : Determinism.PER_INVOCATION; |
| } |
| |
| @Override |
| public boolean isCloneExpression() { |
| return isCloneExpressionByDeterminism(this); |
| } |
| |
| @Override |
| public boolean isStateless() { |
| return true; |
| } |
| |
| // take the random object onto account |
| @Override |
| public int hashCode() { |
| int hashCode = super.hashCode(); |
| return hasSeed ? hashCode : (hashCode + random.hashCode()); |
| } |
| |
| // take the random object onto account, as otherwise we'll potentially collapse two |
| // RAND() calls into a single one. |
| @Override |
| public boolean equals(Object obj) { |
| return super.equals(obj) && (hasSeed || random.equals(((RandomFunction)obj).random)); |
| } |
| |
| // make sure we do not show the default 'null' parameter |
| @Override |
| public final String toString() { |
| StringBuilder buf = new StringBuilder(getName() + "("); |
| if (!hasSeed) return buf.append(")").toString(); |
| for (int i = 0; i < children.size() - 1; i++) { |
| buf.append(children.get(i) + ", "); |
| } |
| buf.append(children.get(children.size()-1) + ")"); |
| return buf.toString(); |
| } |
| } |