项目方案：基于ES Count的Java去重方案

1. 项目背景

在使用 Elasticsearch（ES） 进行数据检索时，我们通常会使用 count API 来获取满足条件的文档数量。然而，有时候我们需要对这些文档进行去重操作，以便得到真正的唯一文档数量。本项目旨在实现一个基于 ES Count 的 Java 方案，用于对文档进行去重操作。

2. 方案概述

本方案将通过以下步骤实现基于 ES Count 的 Java 去重功能：

  1. 使用 Elasticsearch 的 count API 获取符合条件的文档数量。
  2. 使用 Scroll API 迭代地获取所有满足条件的文档数据。
  3. 在内存中对文档数据进行去重操作，得到唯一的文档数量。

3. 技术栈

  • Java 8
  • Elasticsearch Java High-Level REST Client

4. 方案详细步骤

4.1 准备工作

首先，确保已经安装并启动了 Elasticsearch，并将相应的 Maven 依赖添加到项目的 pom.xml 文件中：

<dependency>
    <groupId>org.elasticsearch.client</groupId>
    <artifactId>elasticsearch-rest-high-level-client</artifactId>
    <version>7.15.1</version>
</dependency>

4.2 使用 Elasticsearch Count API 获取文档数量

import org.apache.http.HttpHost;
import org.elasticsearch.client.RestClient;
import org.elasticsearch.client.RestHighLevelClient;
import org.elasticsearch.client.indices.CreateIndexRequest;
import org.elasticsearch.client.indices.CreateIndexResponse;
import org.elasticsearch.client.indices.GetIndexRequest;
import org.elasticsearch.client.indices.GetIndexResponse;
import org.elasticsearch.client.indices.PutMappingRequest;
import org.elasticsearch.client.indices.PutMappingResponse;
import org.elasticsearch.common.xcontent.XContentType;
import org.elasticsearch.index.query.QueryBuilders;
import org.elasticsearch.index.reindex.BulkByScrollResponse;
import org.elasticsearch.index.reindex.DeleteByQueryRequest;
import org.elasticsearch.search.builder.SearchSourceBuilder;

public class ESCountDeduplicationExample {

    private static final String INDEX_NAME = "my_index";
    private static final String DOCUMENT_TYPE = "my_type";

    public static void main(String[] args) throws Exception {
        RestHighLevelClient client = new RestHighLevelClient(
                RestClient.builder(new HttpHost("localhost", 9200, "http")));

        // 创建索引
        createIndex(client);

        // 将文档数据添加到索引中
        addDocuments(client, INDEX_NAME, DOCUMENT_TYPE);

        // 获取文档数量
        long documentCount = getDocumentCount(client, INDEX_NAME, DOCUMENT_TYPE);
        System.out.println("Total document count: " + documentCount);

        client.close();
    }

    private static void createIndex(RestHighLevelClient client) throws Exception {
        GetIndexRequest getIndexRequest = new GetIndexRequest(INDEX_NAME);
        if (!client.indices().exists(getIndexRequest)) {
            CreateIndexRequest createIndexRequest = new CreateIndexRequest(INDEX_NAME);
            CreateIndexResponse createIndexResponse = client.indices().create(createIndexRequest);
            if (!createIndexResponse.isAcknowledged()) {
                throw new RuntimeException("Failed to create index: " + INDEX_NAME);
            }
        }

        PutMappingRequest putMappingRequest = new PutMappingRequest(INDEX_NAME);
        putMappingRequest.source("{\"properties\": {}}", XContentType.JSON);
        PutMappingResponse putMappingResponse = client.indices().putMapping(putMappingRequest);
        if (!putMappingResponse.isAcknowledged()) {
            throw new RuntimeException("Failed to put mapping for index: " + INDEX_NAME);
        }
    }

    private static void addDocuments(RestHighLevelClient client, String index, String type) throws Exception {
        // 添加文档数据到索引中
    }

    private static long getDocumentCount(RestHighLevelClient client, String index, String type) throws Exception {
        SearchSourceBuilder sourceBuilder = new SearchSourceBuilder()
                .query(QueryBuilders.matchAllQuery());

        // 使用 Count API 获取文档数量
        SearchRequest searchRequest = new SearchRequest(index)
                .types(type)
                .source(sourceBuilder);

        SearchResponse searchResponse = client.search(searchRequest);
        return searchResponse.getHits().getTotalHits().value;
    }
}

4.3 使用 Scroll API 迭代获取文档数据

private static List<Map<String, Object>> getDocuments(RestHighLevelClient client, String index, String type, int batchSize) throws Exception {
    List<Map<String, Object>> documents = new ArrayList<>();
    String scrollId = null;
    SearchHit[] searchHits = null;

    while (true) {
        SearchRequest searchRequest = new SearchRequest(index)
                .types(type)
                .scroll(TimeValue.timeValueMinutes(1));