[大数据]C#使用Elasticsearch(NEST)

本文介绍C#使用Elasticsearch的基本方法，并提供一个demo
以下说明中包含的http调用，为ElasticsearchTestController中编写的测试方法

初始化

引用NEST
创建ElasticClient对象

ElasticClient elasticClient = new ElasticClient(new ConnectionSettings(new Uri(address));

新增索引

关键代码

CreateIndexResponse createIndexResponse = await elasticClient.Indices.CreateAsync(indexName, createIndexDescriptor =>
{
    return createIndexDescriptor.
        Map(typeMappingDescriptor =>
        {
            return typeMappingDescriptor.Properties(propertiesSelector =>
            {
                foreach (PropertyInfo propertyInfo in typeof(StudentForElasticsearch).GetProperties())
                {
                    if (!propertyInfo.CanWrite)
                        continue;

                    switch (propertyInfo.PropertyType.Name)
                    {
                        case nameof(Int16):
                        case nameof(Int32):
                        case nameof(Int64):
                        case nameof(UInt16):
                        case nameof(UInt32):
                        case nameof(UInt64):
                        case nameof(Decimal):
                        case nameof(Single):
                        case nameof(Double):
                        case nameof(Byte):
                            propertiesSelector = propertiesSelector.Number(propertyDescriptor => propertyDescriptor.Name(ToJavaScriptPropertyName(propertyInfo.Name)));
                            break;

                        case nameof(Boolean):
                            propertiesSelector = propertiesSelector.Boolean(propertyDescriptor => propertyDescriptor.Name(ToJavaScriptPropertyName(propertyInfo.Name)));
                            break;

                        case nameof(DateTime):
                            propertiesSelector = propertiesSelector.Date(propertyDescriptor => propertyDescriptor.Name(ToJavaScriptPropertyName(propertyInfo.Name)));
                            break;

                        case nameof(String):
                            propertiesSelector = propertiesSelector.Keyword(propertyDescriptor => propertyDescriptor.Name(ToJavaScriptPropertyName(propertyInfo.Name)));
                            break;

                        default:
                            break;
                    }
                }

                return propertiesSelector;
            });
        });
});

为索引添加别名

PutAliasResponse putAliasResponse = await elasticClient.Indices.PutAliasAsync(indexName, indexAliasName);

调用http://localhost:5000/api/ElasticsearchTest/CreateIndex?indexName=stu&indexAliasName=stuAliasName创建索引

查询索引结构

GET
http://xxxxxxx:9200/stu/_mapping 
返回结果   
{
    "stu": {
        "mappings": {
            "properties": {
                "email": {
                    "type": "keyword"
                },
                "id": {
                    "type": "float"
                },
                "name": {
                    "type": "keyword"
                }
            }
        }
    }
}

新增数据

关键代码

BulkResponse bulkResponse = await elasticClient.BulkAsync(bulkDescriptor =>
{
    foreach (StudentForElasticsearch document in datas)
    {
        bulkDescriptor = bulkDescriptor.Index<StudentForElasticsearch>(bulkIndexDescriptor =>
        {
            return bulkIndexDescriptor.Index(indexAliasName).Id(document.Id).Document(document);
        });
    }

    return bulkDescriptor;
});

调用http://localhost:5000/api/ElasticsearchTest/AddOrUpdateData?indexAliasName=stuAliasName新增数据

此时查询数据

GET
http://xxxxxxx:9200/stu/_search
{
    "from": 0,
    "size": 1000
}
返回结果
{
    "took": 33,
    "timed_out": false,
    "_shards": {
        "total": 1,
        "successful": 1,
        "skipped": 0,
        "failed": 0
    },
    "hits": {
        "total": {
            "value": 2,
            "relation": "eq"
        },
        "max_score": 1.0,
        "hits": [
            {
                "_index": "stu",
                "_type": "_doc",
                "_id": "1",
                "_score": 1.0,
                "_source": {
                    "id": 1,
                    "name": "Student1",
                    "email": "11111@qq.com"
                }
            },
            {
                "_index": "stu",
                "_type": "_doc",
                "_id": "2",
                "_score": 1.0,
                "_source": {
                    "id": 2,
                    "name": "Student2",
                    "email": "2222@qq.com"
                }
            }
        ]
    }
}

查询

关键代码

ISearchResponse<StudentForElasticsearch> searchResponse = await elasticClient.SearchAsync<StudentForElasticsearch>(searchDescriptor =>
{
    return searchDescriptor.Index(indexAliasName).Query(queryContainerDescriptor =>
    {
        return queryContainerDescriptor.Bool(boolQueryDescriptor =>
        {
            if (!string.IsNullOrEmpty(name))
            {
                IList<Func<QueryContainerDescriptor<StudentForElasticsearch>, QueryContainer>> queryContainers = new List<Func<QueryContainerDescriptor<StudentForElasticsearch>, QueryContainer>>();

                queryContainers.Add(queryContainerDescriptor =>
                {
                    return queryContainerDescriptor.Wildcard(c => c
                            .Field(ToJavaScriptPropertyName(nameof(StudentForElasticsearch.Name))).Value($"{name}*"));
                });
                boolQueryDescriptor.Must(x => x.Bool(b => b.Should(queryContainers)));
            }
            
            return boolQueryDescriptor;
        });
    })
    .From(0).Size(10);
});

这里采用Wildcard查询，并且只查询前10个匹配数据
调用http://localhost:5000/api/ElasticsearchTest/Get?indexAliasName=stuAliasName&name=Student2
返回结果

[{"id":2,"name":"Student2","email":"2222@qq.com"}]

删除数据

关键代码

BulkResponse bulkResponse = await elasticClient.BulkAsync(bulkDescriptor =>
{
    foreach (int id in deleteIds)
    {
        bulkDescriptor = bulkDescriptor.Delete<StudentForElasticsearch>(bulkIndexDescriptor =>
        {
            return bulkIndexDescriptor.Index(indexAliasName).Id(id);
        });
    }

    return bulkDescriptor;
});

调用http://localhost:5000/api/ElasticsearchTest/DeleteData?indexAliasName=stuAliasName
此时再查询数据，只剩下id为2的数据了