Norm Removal Machine

gistfile1.java

	@Override
	public float tf(float freq) {
	  //original: return (float)Math.sqrt(freq);
	  return (float)Math.sqrt(Math.min(10, freq));
	}

NormRemovalSimilarity.java

package org.elasticsearch.index.similarity;

import org.apache.lucene.search.similarities.DefaultSimilarity;
import org.elasticsearch.common.logging.ESLogger;
import org.elasticsearch.common.logging.Loggers;

public class NormRemovalSimilarity extends DefaultSimilarity {

	private ESLogger logger;

	public NormRemovalSimilarity() {
		logger = Loggers.getLogger(getClass());
	}

	/**
	 * Eliminate the field norm value
	 * @param b ignored
	 * @return Always return 1.0
	 */
	@Override
	public float decodeNormValue(byte b) {
		if (logger.isDebugEnabled()) {
			float norm = super.decodeNormValue(b);
			logger.debug(String.format("Ignore norm: %s => %s", b, norm));
		}

		return 1.0f;
	}
}

NormRemovalSimilarityProvider.java

package org.elasticsearch.index.similarity;

import org.elasticsearch.common.inject.Inject;
import org.elasticsearch.common.inject.assistedinject.Assisted;
import org.elasticsearch.common.settings.Settings;

public class NormRemovalSimilarityProvider extends AbstractSimilarityProvider {

	private NormRemovalSimilarity similarity;

	@Inject
	public NormRemovalSimilarityProvider(@Assisted String name, @Assisted Settings settings) {
		super(name);
		this.similarity = new NormRemovalSimilarity();
	}

	/**
	 * {@inheritDoc}
	 */
	@Override
	public NormRemovalSimilarity get() {
		return similarity;
	}
}

pom.xml

<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0"
         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
         xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
    <modelVersion>4.0.0</modelVersion>

    <groupId>example</groupId>
    <artifactId>norm_removal_similarity</artifactId>
    <version>1.0-SNAPSHOT</version>
    <packaging>jar</packaging>

    <properties>
        <elasticsearch.version>1.1.0</elasticsearch.version>
    </properties>

    <dependencies>
        <dependency>
            <groupId>org.elasticsearch</groupId>
            <artifactId>elasticsearch</artifactId>
            <version>${elasticsearch.version}</version>
            <scope>compile</scope>
        </dependency>
    </dependencies>

</project>