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// Copyright Vespa.ai. Licensed under the terms of the Apache 2.0 license. See LICENSE in the project root.
package com.yahoo.prelude.query;
import com.yahoo.compress.IntegerCompressor;
import com.yahoo.prelude.query.textualrepresentation.Discloser;
import java.nio.ByteBuffer;
import java.util.Objects;
/**
* Weak And of a collection of sub-expressions:
* this behaves like an OR unless many hits are returned and then
* it starts acting more like an AND.
* Alternately it can be viewed as an n-of-m operator where n
* is 1 at first and then increases gradually to m as more hits
* are seen.
*
* @author arnej27959
*/
public final class WeakAndItem extends NonReducibleCompositeItem {
/** The default N used if none is specified: 100 */
public static final int defaultN = 100;
private int n;
private String index;
/** Creates a WAND item with default N */
public WeakAndItem() {
this(defaultN);
}
public WeakAndItem(int N) {
this("", N);
}
/**
* Make a WeakAnd item with no children. You can mention a common index or you can mention it on each child.
*
* @param index the index to search
* @param n the target for minimum number of hits to produce;
* a backend will not suppress any hits in the operator
* until N hits have been produced.
*/
public WeakAndItem(String index, int n) {
this.n = n;
this.index = (index == null) ? "" : index;
}
@Override
public ItemType getItemType() { return ItemType.WEAK_AND; }
@Override
public String getName() { return "WEAKAND"; }
/**
* Sets the default index name to apply to all child items of this.
* This is useful in conjunction with using {@link PureWeightedItem}s as children.
*/
@Override
public void setIndexName(String index) {
String toSet = (index == null) ? "" : index;
super.setIndexName(toSet);
this.index = toSet;
}
/** Returns the index name set for this, or null if none. */
public String getIndexName() { return index; }
/** Appends the heading of this string - <code>[getName()]([limit]) </code> */
@Override
protected void appendHeadingString(StringBuilder buffer) {
buffer.append(getName());
buffer.append("(");
buffer.append(n);
buffer.append(") ");
}
public int getN() { return n; }
public void setN(int N) { this.n = N; }
@Override
protected void encodeThis(ByteBuffer buffer) {
super.encodeThis(buffer);
IntegerCompressor.putCompressedPositiveNumber(n, buffer);
putString(index, buffer);
}
@Override
public void disclose(Discloser discloser) {
super.disclose(discloser);
discloser.addProperty("N", n);
}
@Override
public int hashCode() { return Objects.hash(super.hashCode(), n, index); }
/** Returns whether this item is of the same class and contains the same state as the given item. */
@Override
public boolean equals(Object object) {
if (!super.equals(object)) return false;
WeakAndItem other = (WeakAndItem) object; // Ensured by superclass
if (this.n != other.n) return false;
if ( ! Objects.equals(this.index, other.index)) return false;
return true;
}
}
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