es中fetch_size

fetch_size是Java JDBC驱动程序中的一个属性，用于指定从数据库中一次性获取的记录行数。它用于优化数据库操作的性能，因为较大的值可以减少与数据库的通信次数，从而减少网络延迟和资源消耗。在Elasticsearch中，fetch_size没有与JDBC API相关的应用场景，因为Elasticsearch是一个NoSQL数据库，不使用JDBC API。

相关问题

cpu_sys_in_millis cpu_user_in_millis merge_threads merge_queue merge_active merge_rejected merge_largest merge_completed bulk_threads bulk_queue bulk_active bulk_rejected bulk_largest bulk_completed warmer_threads warmer_queue warmer_active warmer_rejected warmer_largest warmer_completed get_largest get_completed get_threads get_queue get_active get_rejected index_threads index_queue index_active index_rejected index_largest index_completed suggest_threads suggest_queue suggest_active suggest_rejected suggest_largest suggest_completed fetch_shard_store_queue fetch_shard_store_active fetch_shard_store_rejected fetch_shard_store_largest fetch_shard_store_completed fetch_shard_store_threads management_threads management_queue management_active management_rejected management_largest management_completed percolate_queue percolate_active percolate_rejected percolate_largest percolate_completed percolate_threads listener_active listener_rejected listener_largest listener_completed listener_threads listener_queue search_rejected search_largest search_completed search_threads search_queue search_active fetch_shard_started_threads fetch_shard_started_queue fetch_shard_started_active fetch_shard_started_rejected fetch_shard_started_largest fetch_shard_started_completed refresh_rejected refresh_largest refresh_completed refresh_threads refresh_queue refresh_active optimize_threads optimize_queue optimize_active optimize_rejected optimize_largest optimize_completed snapshot_largest snapshot_completed snapshot_threads snapshot_queue snapshot_active snapshot_rejected generic_threads generic_queue generic_active generic_rejected generic_largest generic_completed flush_threads flush_queue flush_active flush_rejected flush_largest flush_completed server_open rx_count rx_size_in_bytes tx_count tx_size_in_bytes

这些指标是Elasticsearch集群监控指标，包括：

- cpu_sys_in_millis：集群中所有节点的系统CPU使用时间，即内核态时间。
- cpu_user_in_millis：集群中所有节点的用户CPU使用时间，即用户态时间。
- merge_threads/merge_queue/merge_active/merge_rejected/merge_largest/merge_completed：用于合并段（segments）的线程池监控指标。
- bulk_threads/bulk_queue/bulk_active/bulk_rejected/bulk_largest/bulk_completed：用于批量操作的线程池监控指标。
- warmer_threads/warmer_queue/warmer_active/warmer_rejected/warmer_largest/warmer_completed：用于预热索引的线程池监控指标。
- get_largest/get_completed/get_threads/get_queue/get_active/get_rejected：用于处理get请求的线程池监控指标。
- index_threads/index_queue/index_active/index_rejected/index_largest/index_completed：用于处理index请求的线程池监控指标。
- suggest_threads/suggest_queue/suggest_active/suggest_rejected/suggest_largest/suggest_completed：用于处理suggest请求的线程池监控指标。
- fetch_shard_store_queue/fetch_shard_store_active/fetch_shard_store_rejected/fetch_shard_store_largest/fetch_shard_store_completed/fetch_shard_store_threads：用于获取分片数据的线程池监控指标。
- management_threads/management_queue/management_active/management_rejected/management_largest/management_completed：用于管理操作的线程池监控指标。
- percolate_queue/percolate_active/percolate_rejected/percolate_largest/percolate_completed/percolate_threads：用于处理percolate请求的线程池监控指标。
- listener_active/listener_rejected/listener_largest/listener_completed/listener_threads/listener_queue：用于处理请求的监听器监控指标。
- search_rejected/search_largest/search_completed/search_threads/search_queue/search_active：用于处理search请求的线程池监控指标。
- fetch_shard_started_threads/fetch_shard_started_queue/fetch_shard_started_active/fetch_shard_started_rejected/fetch_shard_started_largest/fetch_shard_started_completed：用于获取分片数据的线程池监控指标。
- refresh_rejected/refresh_largest/refresh_completed/refresh_threads/refresh_queue/refresh_active：用于刷新操作的线程池监控指标。
- optimize_threads/optimize_queue/optimize_active/optimize_rejected/optimize_largest/optimize_completed：用于优化操作的线程池监控指标。
- snapshot_largest/snapshot_completed/snapshot_threads/snapshot_queue/snapshot_active/snapshot_rejected：用于快照操作的线程池监控指标。
- generic_threads/generic_queue/generic_active/generic_rejected/generic_largest/generic_completed：用于处理通用请求的线程池监控指标。
- flush_threads/flush_queue/flush_active/flush_rejected/flush_largest/flush_completed：用于刷新操作的线程池监控指标。
- server_open：当前打开的HTTP连接数。
- rx_count/rx_size_in_bytes：接收的HTTP请求数和数据量。
- tx_count/tx_size_in_bytes：发送的HTTP响应数和数据量。

这些指标可以帮助我们监控Elasticsearch集群的运行状态和性能，及时发现并解决潜在的问题。

java实现es分页查询_如何在elasticsearch里面使用深度分页功能

在 Elasticsearch 中使用深度分页功能需要注意以下几点：

1. 尽量避免使用深度分页功能，因为它会增加网络和计算开销，可能导致性能问题。

2. 深度分页功能是通过设置 from 和 size 参数来实现的。from 参数表示从哪个位置开始查询，size 参数表示每页返回的文档数量。

3. Elasticsearch 默认最多只能返回 10000 条记录，如果需要查询更多的记录，需要设置 index.max_result_window 参数。但是设置太大会占用过多的内存，影响性能。

下面是一个 Java 实现 Elasticsearch 分页查询的示例代码：

import org.elasticsearch.action.search.SearchResponse;
import org.elasticsearch.action.search.SearchType;
import org.elasticsearch.client.Client;
import org.elasticsearch.index.query.QueryBuilders;
import org.elasticsearch.search.SearchHit;
import org.elasticsearch.search.SearchHits;
import org.elasticsearch.search.sort.SortBuilders;
import org.elasticsearch.search.sort.SortOrder;

public class ESQuery {
    private Client client;

    public ESQuery(Client client) {
        this.client = client;
    }

    public void search(String index, String type, int from, int size) {
        SearchResponse response = client.prepareSearch(index)
                .setTypes(type)
                .setQuery(QueryBuilders.matchAllQuery())
                .addSort(SortBuilders.fieldSort("_id").order(SortOrder.DESC))
                .setSearchType(SearchType.DFS_QUERY_THEN_FETCH)
                .setFrom(from)
                .setSize(size)
                .execute()
                .actionGet();

        SearchHits hits = response.getHits();
        for (SearchHit hit : hits) {
            System.out.println(hit.getSourceAsString());
        }
    }
}

调用示例：

ESQuery esQuery = new ESQuery(client);
esQuery.search("my_index", "my_type", 0, 10); // 查询第一页，每页10条记录
esQuery.search("my_index", "my_type", 10, 10); // 查询第二页，每页10条记录，从第11条记录开始