| /* |
| * 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.segment.virtual; |
| |
| import com.google.common.base.Preconditions; |
| import it.unimi.dsi.fastutil.longs.Long2ObjectLinkedOpenHashMap; |
| import org.apache.druid.java.util.common.ISE; |
| import org.apache.druid.math.expr.Expr; |
| import org.apache.druid.math.expr.ExprEval; |
| import org.apache.druid.query.monomorphicprocessing.RuntimeShapeInspector; |
| import org.apache.druid.segment.ColumnValueSelector; |
| |
| import javax.annotation.Nonnull; |
| import javax.annotation.Nullable; |
| |
| /** |
| * Like {@link ExpressionColumnValueSelector}, but caches the most recently computed value and re-uses it in the case |
| * of runs in the underlying column. This is especially useful for the __time column, where we expect runs. |
| */ |
| public class SingleLongInputCachingExpressionColumnValueSelector implements ColumnValueSelector<ExprEval> |
| { |
| private static final int CACHE_SIZE = 1000; |
| |
| private final ColumnValueSelector selector; |
| private final Expr expression; |
| private final SingleInputBindings bindings = new SingleInputBindings(); |
| |
| @Nullable |
| private final LruEvalCache lruEvalCache; |
| |
| // Last read input value. |
| private long lastInput; |
| |
| // Last computed output value, or null if there is none. |
| @Nullable |
| private ExprEval lastOutput; |
| |
| public SingleLongInputCachingExpressionColumnValueSelector( |
| final ColumnValueSelector selector, |
| final Expr expression, |
| final boolean useLruCache |
| ) |
| { |
| // Verify expression has just one binding. |
| if (expression.analyzeInputs().getRequiredBindings().size() != 1) { |
| throw new ISE("Expected expression with just one binding"); |
| } |
| |
| this.selector = Preconditions.checkNotNull(selector, "selector"); |
| this.expression = Preconditions.checkNotNull(expression, "expression"); |
| this.lruEvalCache = useLruCache ? new LruEvalCache() : null; |
| } |
| |
| @Override |
| public void inspectRuntimeShape(final RuntimeShapeInspector inspector) |
| { |
| inspector.visit("selector", selector); |
| inspector.visit("expression", expression); |
| } |
| |
| @Override |
| public double getDouble() |
| { |
| return getObject().asDouble(); |
| } |
| |
| @Override |
| public float getFloat() |
| { |
| return (float) getObject().asDouble(); |
| } |
| |
| @Override |
| public long getLong() |
| { |
| return getObject().asLong(); |
| } |
| |
| @Nonnull |
| @Override |
| public ExprEval getObject() |
| { |
| // things can still call this even when underlying selector is null (e.g. ExpressionColumnValueSelector#isNull) |
| if (selector.isNull()) { |
| return ExprEval.ofLong(null); |
| } |
| // No assert for null handling, as the delegate selector already has it. |
| final long input = selector.getLong(); |
| final boolean cached = input == lastInput && lastOutput != null; |
| |
| if (!cached) { |
| if (lruEvalCache == null) { |
| bindings.set(input); |
| lastOutput = expression.eval(bindings); |
| } else { |
| lastOutput = lruEvalCache.compute(input); |
| } |
| |
| lastInput = input; |
| } |
| |
| return lastOutput; |
| } |
| |
| @Override |
| public Class<ExprEval> classOfObject() |
| { |
| return ExprEval.class; |
| } |
| |
| @Override |
| public boolean isNull() |
| { |
| // It is possible for an expression to have a non-null String value but it can return null when parsed |
| // as a primitive long/float/double. |
| // ExprEval.isNumericNull checks whether the parsed primitive value is null or not. |
| return getObject().isNumericNull(); |
| } |
| |
| public class LruEvalCache |
| { |
| private final Long2ObjectLinkedOpenHashMap<ExprEval> m = new Long2ObjectLinkedOpenHashMap<>(); |
| |
| public ExprEval compute(final long n) |
| { |
| ExprEval value = m.getAndMoveToFirst(n); |
| |
| if (value == null) { |
| bindings.set(n); |
| value = expression.eval(bindings); |
| m.putAndMoveToFirst(n, value); |
| |
| if (m.size() > CACHE_SIZE) { |
| m.removeLast(); |
| } |
| } |
| |
| return value; |
| } |
| } |
| } |