忽略属性映射

概述

实体类中的属性映射可以通过多种方式进行忽略：

• 在继承自ElasticsearchPropertyAttributeBase类型的属性上使用Ignore参数，比如TextAttribute特性

• 在PropertyNameAttribute特性上设置Ignore参数

• 在ConnectionSettings连接配置中设置.DefaultMappingFor<TDocument>(Func<ClrTypeMappingDescriptor<TDocument>, IClrTypeMapping<TDocument>> selector)

以下示例演示了几种忽略属性映射的方式：

[ElasticsearchType(RelationName = "company")]
public class CompanyWithAttributesAndPropertiesToIgnore
{
    public string Name { get; set; }

    [Text(Ignore = true)]
    public string PropertyToIgnore { get; set; }

    [PropertyName("anotherPropertyToIgnore", Ignore = true)]
    public string AnotherPropertyToIgnore { get; set; }

    public string FluentMappingPropertyToIgnore { get; set; }

    [Ignore, JsonIgnore]
    public string JsonIgnoredProperty { get; set; }
}

以下示例演示映射中除了Name之外的所有属性都被忽略：

var connectionSettings = new ConnectionSettings(new InMemoryConnection()) 
    .DisableDirectStreaming() 
    .DefaultMappingFor<CompanyWithAttributesAndPropertiesToIgnore>(m => m
        .Ignore(p => p.FluentMappingPropertyToIgnore)
    );

var client = new ElasticClient(connectionSettings);

var createIndexResponse = client.Indices.Create("myindex", c => c
    .Map<CompanyWithAttributesAndPropertiesToIgnore>(m => m
        .AutoMap()
    )
);

输出的JSON结果中不包含被忽略的属性：

{
  "mappings": {
    "properties": {
      "name": {
        "type": "text",
        "fields": {
          "keyword": {
            "type": "keyword",
            "ignore_above": 256
          }
        }
      }
    }
  }
}

忽略继承的属性

在ConnectionSettings的DefaultMappingFor<T>中配置的忽略属性，对来自继承的属性也生效，如下：

public class Parent
{
    public int Id { get; set; }
    public string Description { get; set; }
    public string IgnoreMe { get; set; }
}

public class Child : Parent { }

var connectionSettings = new ConnectionSettings(new InMemoryConnection())
        .DisableDirectStreaming()
        .DefaultMappingFor<Child>(m => m
            .PropertyName(p => p.Description, "desc")
            .Ignore(p => p.IgnoreMe)
        );

var client = new ElasticClient(connectionSettings);

var createIndexResponse = client.Indices.Create("myindex", c => c
        .Map<Child>(m => m
            .AutoMap()
        )
    );

由于在DefaultMappingFor<Child>中配置了.Ignore(p => p.IgnoreMe)，所以父类中的IgnoreMe属性在子类中也被忽略了，得到的JSON结果为：

{
  "mappings": {
    "properties": {
      "id": {
        "type": "integer"
      },
      "desc": {
        "fields": {
          "keyword": {
            "ignore_above": 256,
            "type": "keyword"
          }
        },
        "type": "text"
      }
    }
  }
}

重写继承属性的映射

ConnectionSettings连接配置中的DefaultMappingFor<T>()方法还可以重写继承属性的映射关系，在接下来的示例中，Id属性被ParentWithStringId重写成了string类型，结果导致NEST将其推断为text并默认设置了多字段属性类型映射：

public class ParentWithStringId : Parent
{
    public new string Id { get; set; }
}

var connectionSettings = new ConnectionSettings(new InMemoryConnection()) 
        .DisableDirectStreaming() 
        .DefaultMappingFor<ParentWithStringId>(m => m
            .Ignore(p => p.Description)
            .Ignore(p => p.IgnoreMe)
        );

var client = new ElasticClient(connectionSettings);

var createIndexResponse = client.Indices.Create("myindex", c => c
        .Map<ParentWithStringId>(m => m
            .AutoMap()
        )
    );

得到的JSON映射结果为：

{
  "mappings": {
    "properties": {
      "id": {
        "type": "text",
        "fields": {
          "keyword": {
            "ignore_above": 256,
            "type": "keyword"
          }
        }
      }
    }
  }
}