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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.prelude.query;
import com.yahoo.compress.IntegerCompressor;
import com.yahoo.prelude.query.textualrepresentation.Discloser;
import java.nio.ByteBuffer;
/**
* A weighted set query item to be evaluated as a Wand with dot product scoring.
*
* The dot product is calculated between the matched tokens of the weighted set field searched
* and the weights associated with the tokens of this WandItem.
* The resulting dot product will be available as a raw score in the rank framework.
*
* @author geirst
*/
public class WandItem extends WeightedSetItem {
private int targetNumHits;
private double scoreThreshold = 0;
private double thresholdBoostFactor = 1;
/**
* Creates an empty WandItem.
*
* @param fieldName the name of the weighted set field to search with this WandItem.
* @param targetNumHits the target for minimum number of hits to produce by the backend search operator handling this WandItem.
*/
public WandItem(String fieldName, int targetNumHits) {
super(fieldName);
this.targetNumHits = targetNumHits;
}
/**
* Sets the initial score threshold used by the backend search operator handling this WandItem.
* The score of a document must be larger than this threshold in order to be considered a match.
* Default value is 0.0.
*
* @param scoreThreshold the initial score threshold.
*/
public void setScoreThreshold(double scoreThreshold) {
this.scoreThreshold = scoreThreshold;
}
/**
* Sets the boost factor used by the backend search operator to boost the threshold before
* comparing it with the upper bound score of the document being evaluated.
* A large value of this factor results in fewer full evaluations and in an expected loss in precision.
* Similarly, a gain in performance might be expected. Default value is 1.0.
*
* NOTE: This boost factor is only used when this WandItem is searching a Vespa field.
*
* @param thresholdBoostFactor the boost factor.
*/
public void setThresholdBoostFactor(double thresholdBoostFactor) {
this.thresholdBoostFactor = thresholdBoostFactor;
}
public int getTargetNumHits() {
return targetNumHits;
}
public double getScoreThreshold() {
return scoreThreshold;
}
public double getThresholdBoostFactor() {
return thresholdBoostFactor;
}
@Override
public ItemType getItemType() {
return ItemType.WAND;
}
@Override
protected void encodeThis(ByteBuffer buffer) {
super.encodeThis(buffer);
IntegerCompressor.putCompressedPositiveNumber(targetNumHits, buffer);
buffer.putDouble(scoreThreshold);
buffer.putDouble(thresholdBoostFactor);
}
@Override
protected void appendHeadingString(StringBuilder buffer) {
buffer.append(getName());
buffer.append("(");
buffer.append(targetNumHits);
buffer.append(",");
buffer.append(scoreThreshold);
buffer.append(",");
buffer.append(thresholdBoostFactor);
buffer.append(")");
buffer.append(" ");
}
@Override
public void disclose(Discloser discloser) {
super.disclose(discloser);
discloser.addProperty("targetNumHits", targetNumHits);
discloser.addProperty("scoreThreshold", scoreThreshold);
discloser.addProperty("thresholdBoostFactor", thresholdBoostFactor);
}
}
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