postgresql - 将来自 JSON 数组对象字段的数据与另一个表连接起来
问题描述
比方说,我在 Postgre 数据库上有两个表,如下所示:
CREATE TABLE "MST"."Users" (
"Id" uuid NOT NULL DEFAULT uuid_generate_v4(),
"Uid" varchar(32) COLLATE "pg_catalog"."default" NOT NULL,
"Pid" varchar(100) COLLATE "pg_catalog"."default" NOT NULL,
"Details" jsonb,
"Contacts" jsonb,
"Trackers" jsonb NOT NULL,
"Configurations" jsonb,
PRIMARY KEY ("Id"),
UNIQUE ("Uid")
);
CREATE TABLE "MST"."Teams" (
"Id" uuid NOT NULL DEFAULT uuid_generate_v4(),
"Details" jsonb NOT NULL,
"Members" jsonb,
"Trackers" jsonb NOT NULL,
PRIMARY KEY ("Id")
);
这两个表都映射了以下模型:
[Table("Users", Schema = "MST")]
public partial class Users
{
[Key]
public Guid Id { get; set; }
[Required]
[StringLength(32)]
public string Uid { get; set; }
[Required]
[StringLength(100)]
public string Pid { get; set; }
[Column(TypeName = "jsonb")]
public UserDetailsModel Details { get; set; }
[Column(TypeName = "jsonb")]
public UserContactsModel Contacts { get; set; }
[Required]
[Column(TypeName = "jsonb")]
public TrackersModel Trackers { get; set; }
[Column(TypeName = "jsonb")]
public UserConfigurationsModel Configurations { get; set; }
}
[Table("Teams", Schema = "MST")]
public partial class Teams
{
[Key]
public Guid Id { get; set; }
[Required]
[Column(TypeName = "jsonb")]
public TeamDetailsModel Details { get; set; }
[Column(TypeName = "jsonb")]
public List<TeamMembersModel> Members { get; set; }
[Required]
[Column(TypeName = "jsonb")]
public TrackersModel Trackers { get; set; }
}
// Childs classes
public class TeamMembersModel
{
[Required(ErrorMessage = @"Member ""User ID"" is required and can not be empty.")]
[StringLength(maximumLength: 32, MinimumLength = 3, ErrorMessage = @"Member ""User ID"" length must be between 3 and 32 chars.")]
public string Uid { get; set; }
public bool IsLead { get; set; } = false;
public UserDetailsModel Details { get; set; }
}
public UserContactModel {
...some properties...
}
public TrackersModel {
...some properties...
}
public UserDetailsModel {
...some properties...
}
以下是Teams表中的数据示例:
INSERT INTO "MST"."Teams"("Id", "Details", "Members", "Trackers") VALUES ('daf0e3d3-78bf-443b-8b0b-6f74d2eabd7f', '{"Name": "My First Team", "Files": [], "Notes": null, "Photo": null}', '[{"Uid": "fadhly.permata", "IsLead": true}, {"Uid": "humaira.permata", "IsLead": false}]', '{"Status": "RG", "Created": {"At": "2020-08-14T12:15:59.4175028+00:00", "By": "SYSTEM"}, "Updated": null}');
INSERT INTO "MST"."Teams"("Id", "Details", "Members", "Trackers") VALUES ('538f1d58-01cb-4120-b89a-ea25bfacaa25', '{"Name": "My Second Team", "Files": [], "Notes": null, "Photo": null}', '[{"Uid": "fadhly.permata", "IsLead": true, "Details": null}]', '{"Status": "RG", "Created": {"At": "2020-08-19T10:51:44.5128139+00:00", "By": "fadhly.permata"}, "Updated": null}');
正如您在我的数据库数据中看到的那样,成员字段与 JSON 数组一起存储。我对如何使用用户表中的详细信息加入 Teams->Members->Details 感到困惑。
这是我的查询:
from
team in _manager.DbContext.Teams
where
team.Trackers.Status != "DE"
orderby
team.Details.Name
select
new Models.Teams
{
Id = team.Id,
Details = team.Details,
Trackers = team.Trackers,
Members = team.Members.Select(
x => new TeamMembersModel {
Uid = x.Uid,
IsLead = x.IsLead,
Details = _manager.DbContext.Users.First(y => y.Uid == x.Uid).Details
}
)
.ToList()
};
但我对上述查询没有运气,并收到此错误消息:
"Object reference not set to an instance of an object."
也许,我错过了一些东西,但不确定它在哪里。
注意: 我使用NPGSQL作为 EF 引擎的附加/扩展,因为我也添加了这个问题标签。
解决方案
问题在于您的 投影team.Members
,它是 JSON 属性而不是 EF 导航 - 这无法转换为 SQL 以便在 PostgreSQL 中进行处理。由于这是最终的预测,这应该只是得到客户评估,但 EF 似乎有一个错误(打开https://github.com/dotnet/efcore/issues/22161进行跟踪)。
如果目的是让客户评估,只需在投影之前放置一个 AsEnumerable - 这应该会使错误消失。除此以外,
理论上,这可以通过将 JSON 数组投影转换为json_array_elements
(请参阅 PG 文档)来完成,但提供者极不可能很快做到这一点。
推荐阅读
- c++ - 我如何在 C++ 中声明一个类
- javascript - DOM JS - 对象 HTMLUnknownElement
- python - Python 通过 cursor.execute 和 mysql 损坏导入的 csv 文件
- swift - 我们如何在 SwiftUi 的另一个视图中传递布尔状态
- date - 用 datepicker 选择的日期取前一天的值
- java - 一对一休眠,不生成外键
- matplotlib - 在 Seaborn 图中对齐多行刻度
- javascript - JavaScript 在使用 Node 调用时有效,但仅在从 HTML 调用时才有效
- python - 为什么我的类更新函数没有更新我的变量
- r - R 中 ifelse 和 is.table 或 is.matrix 的问题