PostgresException: 23505: duplicate key value violates unique constraint “PK_country”

问题

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

PostgresException: 23505: duplicate key value violates unique constraint "PK_country"

By tracing it looks like EF doesnt generate AutoIncrement column

My Model

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

My Controller

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

Exception

> 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()

What could be the problem?

回答1:

I found the solution. The issue was I was seed the database with the script from the sql file.

context.Database.ExecuteSqlCommand(File.ReadAllText(baseDir + "\\data.sql"));

The insert contains

ALTER TABLE country DISABLE TRIGGER ALL;
INSERT INTO country .......

So the sequence current value was not updating. Current value remained 1.So when I inserted with application. Autoincrment become 1 hence PostgresException: 23505: duplicate key value violates unique constraint "PK_country".

Resolution

After ALTER TABLE country ENABLE TRIGGER ALL; add SELECT pg_catalog.setval(pg_get_serial_sequence('country', 'country_id'), MAX(country_id)) FROM country;

Now it application run successifully.

Hope help someone else.

回答2:

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" });

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.

This happens with:

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

来源：https://stackoverflow.com/questions/47961531/postgresexception-23505-duplicate-key-value-violates-unique-constraint-pk-cou

标签

entity-framework

entity-framework-core

asp.net-core-2.0

npgsql