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// Copyright 2017 Yahoo Holdings. Licensed under the terms of the Apache 2.0 license. See LICENSE in the project root.
package com.yahoo.search.query.profile.compiled;
import com.yahoo.search.query.profile.DimensionBinding;
import java.util.Arrays;
import java.util.Collections;
import java.util.HashMap;
import java.util.Map;
/**
* An immutable binding of a set of dimensions to values.
* This binding is minimal in that it only includes dimensions which actually have values.
*
* @author bratseth
*/
public class Binding implements Comparable<Binding> {
private static final int maxDimensions = 31;
/**
* A higher number means this is more general. This accounts for both the number and position of the bindings
* in the dimensional space, such that bindings in earlier dimensions are matched before bindings in
* later dimensions
*/
private final int generality;
/** The dimensions of this. Unenforced invariant: Content never changes. */
private final String[] dimensions;
/** The values of those dimensions. Unenforced invariant: Content never changes. */
private final String[] dimensionValues;
private final int hashCode;
@SuppressWarnings("unchecked")
public static final Binding nullBinding = new Binding(Integer.MAX_VALUE, Collections.<String,String>emptyMap());
public static Binding createFrom(DimensionBinding dimensionBinding) {
if (dimensionBinding.getDimensions().size() > maxDimensions)
throw new IllegalArgumentException("More than 31 dimensions is not supported");
int generality = 0;
Map<String, String> context = new HashMap<>();
if (dimensionBinding.getDimensions() == null || dimensionBinding.getDimensions().isEmpty()) { // TODO: Just have this return the nullBinding
generality = Integer.MAX_VALUE;
}
else {
for (int i = 0; i <= maxDimensions; i++) {
String value = i < dimensionBinding.getDimensions().size() ? dimensionBinding.getValues().get(i) : null;
if (value == null)
generality += Math.pow(2, maxDimensions - i-1);
else
context.put(dimensionBinding.getDimensions().get(i), value);
}
}
return new Binding(generality, context);
}
private Binding(int generality, Map<String, String> binding) {
this.generality = generality;
// Map -> arrays to limit memory consumption and speed up evaluation
dimensions = new String[binding.size()];
dimensionValues = new String[binding.size()];
int i = 0;
int bindingHash = 0;
for (Map.Entry<String,String> entry : binding.entrySet()) {
dimensions[i] = entry.getKey();
dimensionValues[i] = entry.getValue();
bindingHash += i * entry.getKey().hashCode() + 11 * i * entry.getValue().hashCode();
i++;
}
this.hashCode = bindingHash;
}
/** Returns true only if this binding is null (contains no values for its dimensions (if any) */
public boolean isNull() { return dimensions.length == 0; }
@Override
public String toString() {
StringBuilder b = new StringBuilder("Binding[");
for (int i = 0; i < dimensions.length; i++)
b.append(dimensions[i]).append("=").append(dimensionValues[i]).append(",");
if (dimensions.length > 0)
b.setLength(b.length()-1);
b.append("] (generality " + generality + ")");
return b.toString();
}
/** Returns whether the given binding has exactly the same values as this */
@Override
public boolean equals(Object o) {
if (o == this) return true;
if (! (o instanceof Binding)) return false;
Binding other = (Binding)o;
return Arrays.equals(this.dimensions, other.dimensions)
&& Arrays.equals(this.dimensionValues, other.dimensionValues);
}
@Override
public int hashCode() { return hashCode; }
/**
* Returns true if all the dimension values in this have the same values
* in the given context.
*/
public boolean matches(Map<String, String> context) {
for (int i = 0; i < dimensions.length; i++) {
if ( ! dimensionValues[i].equals(context.get(dimensions[i]))) return false;
}
return true;
}
/**
* Implements a partial ordering where more specific bindings come before less specific ones,
* taking both the number of bindings and their positions into account (earlier dimensions
* take precedence over later ones.
* <p>
* The order is not well defined for bindings in different dimensional spaces.
*/
@Override
public int compareTo(Binding other) {
return Integer.compare(this.generality, other.generality);
}
}
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