elasticsearch 自定义similarity 插件开发

转自:http://www.chepoo.com/elasticsearch-similarity-custom-plug-in-development.html

在搜索开发中，我们要修改打分机制，就需要自定义similarity。现在来简单说一下elasticsearch下的自定义similarity 插件开发。

网上的https://github.com/tlrx/elasticsearch-custom-similarity-provider仅仅支持0.20.0.Beta1-SNAPSHOT版本，现在我们用的版本是elasticsearch 0.90版本以上。那个例子现在不能用，我修改了一下。

1.继承DefaultSimilarity，实现自己的搜索打分机制。

package org.elasticsearch.index.similarity;

import org.apache.lucene.search.similarities.DefaultSimilarity;

/**
 * Custom similarity class
 *
 * @author xq
 *
 */
public class CustomSimilarity extends DefaultSimilarity {

	@Override
	public float idf(long docFreq, long numDocs) {
		return 1.0f;
	}

}

2.继续AbstractSimilarityProvider，把自定义的打分机制类加载到elasticsearch中。

package org.elasticsearch.index.similarity;

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

/**
 * Simple {@link SimilarityProvider} for a {@link CustomSimilarity}
 *
 * @author xq
 *
 */
public class CustomSimilarityProvider extends AbstractSimilarityProvider {

	private CustomSimilarity similarity;

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

	public CustomSimilarity get() {
		return similarity;
	}
}

3.继承AbstractPlugin作为elasticsearch插件使用

public class CustomerSimilarityPlugin extends AbstractPlugin {

    @Override public String name() {
        return "customer-similarity";
    }

    @Override public String description() {
        return "customer similarity";
    }

    @Override public void processModule(Module module) {
        if (module instanceof SimilarityModule) {
        	SimilarityModule similarityModule = (SimilarityModule) module;
        	similarityModule.addSimilarity("customer-similarity", CustomSimilarityProvider.class);
        }
    }
}

4.使用

curl -XPOST 'http://host:port/tweeter/' -d '
{
  "settings": {
    "similarity": {
      "index": {
        "type": "org.elasticsearch.index.similarity.CustomSimilarityProvider"
      },
      "search": {
        "type": "org.elasticsearch.index.similarity.CustomSimilarityProvider"
      }
    }
  }
}'

在创建mapping的使用自定义的打分规则：

{
  "news" : {
    "properties" : {
      "title" : { "type" : "string", "similarity" : "my_similarity" }
    }
}

在elasticsearch.yml中配置自定义的打分规则类为默认规则。 index.similarity.default.type: my_similarity

相关程序已经放在https://github.com/awnuxkjy/es-custom-similarity-provider,有兴趣的朋友可以参考一下。

把程序打成jar包放在elasticsearch 的plugins 下的 similarity 目录下即可 参考文章： http://www.elasticsearch.org/guide/reference/index-modules/similarity/