PostgresException:23505:重复的键值违反了唯一约束"PK_country".

问题描述

我正在使用EF Core 2.0和Postgres 9.6.每当我插入数据时都会出现错误

I am using EF Core 2.0 and Postgres 9.6. Whenever I insert data I get the error

通过跟踪它看起来像EF不会生成AutoIncrement列

By tracing it looks like EF doesnt generate AutoIncrement column

我的模特

public partial class Country
    {
        [Key]
        [DatabaseGenerated(DatabaseGeneratedOption.Identity)]
        public int CountryId { get; set; }
        [Display(Name="Country Name")]
        public string CountryName { get; set; }
    }

我的控制器

if (ModelState.IsValid)
            {
                _context.Add(country);
                await _context.SaveChangesAsync();
                return RedirectToAction(nameof(Index));
            }

例外

> PostgresException: 23505: duplicate key value violates unique
> constraint "PK_country"
>
>     Npgsql.NpgsqlConnector+<DoReadMessage>d__148.MoveNext()
>     System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()
>     System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task
> task)
>     System.Runtime.CompilerServices.TaskAwaiter.GetResult()
>     System.Runtime.CompilerServices.ValueTaskAwaiter.GetResult()
>     Npgsql.NpgsqlConnector+<ReadMessage>d__147.MoveNext()
>     System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()
>     Npgsql.NpgsqlConnector+<ReadMessage>d__147.MoveNext()
>     System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()
>     System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task
> task)
>     System.Runtime.CompilerServices.TaskAwaiter.GetResult()
>     System.Runtime.CompilerServices.ValueTaskAwaiter.GetResult()
>     Npgsql.NpgsqlDataReader+<NextResult>d__32.MoveNext()
>     System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()
>     System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task
> task)
>     Npgsql.NpgsqlDataReader+<<NextResultAsync>b__31_0>d.MoveNext()
>     System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()
>     System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task
> task)
>     Npgsql.NpgsqlCommand+<Execute>d__71.MoveNext()
>     System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()
>     System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task
> task)
>     System.Runtime.CompilerServices.TaskAwaiter.GetResult()
>     System.Runtime.CompilerServices.ValueTaskAwaiter.GetResult()
>     Npgsql.NpgsqlCommand+<ExecuteDbDataReader>d__92.MoveNext()
>     System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()
>     System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task
> task)
>     System.Runtime.CompilerServices.TaskAwaiter.GetResult()
>     System.Runtime.CompilerServices.ValueTaskAwaiter.GetResult()
>     Npgsql.NpgsqlCommand+<>c__DisplayClass90_0+<<ExecuteDbDataReaderAsync>b__0>d.MoveNext()
>     System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()
>     System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task
> task)
>     System.Runtime.CompilerServices.TaskAwaiter.GetResult()
>     Microsoft.EntityFrameworkCore.Storage.Internal.RelationalCommand+<ExecuteAsync>d__17.MoveNext()
>     System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()
>     System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task
> task)
>     System.Runtime.CompilerServices.TaskAwaiter.GetResult()
>     Microsoft.EntityFrameworkCore.Update.ReaderModificationCommandBatch+<ExecuteAsync>d__32.MoveNext()

可能是什么问题?

推荐答案

即使已经找到了此处的解决方案，该问题也没有指定您从某些.sql文件中加载数据.如果您已通过以下方式加载数据，则也会产生相同的错误:

Even though the solution here was already found, the question does not specify that you load the data from some .sql file. If you had been loading the data in the following way, this would have also generated the same error:

_context.Add(new Country { CountryId = 0, CountryName = "MyCountry" });
_context.Add(new Country { CountryId = 1, CountryName = "MyCountry" });

原因是，(我不知道为什么)第一行将具有CountryId = 1，第二行也将具有CountryId = 1.导致重复的键值.

The reason is, that (I don't know why) the first row will have CountryId = 1 and the second one also CountryId = 1. Which leads to duplicate key value.

这发生在:

• Npgsql.EntityFrameworkCore.PostgreSQL 2.1.2
• Microsoft.EntityFrameworkCore.Design 2.2.3

这篇关于PostgresException:23505:重复的键值违反了唯一约束"PK_country".的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持！