BulkInsert with Identity and PK causes 'duplicate key value' error

[JPL-1]

I am building an app that uses identity columns. I am finding that the identity columns work fine by themselves, and they work fine with a unique index on the identity column. However, if a PK is added (a unique constraint of type Primary Key), then BulkInsert produces the following error.

Npgsql.PostgresException (0x80004005): 23505: duplicate key value violates unique constraint "Test_pKey"

DETAIL: Key (id)=(0) already exists.
at Npgsql.Internal.NpgsqlConnector.ReadMessageLong(Boolean async, DataRowLoadingMode dataRowLoadingMode, Boolean readingNotifications, Boolean isReadingPrependedMessage)
at System.Runtime.CompilerServices.PoolingAsyncValueTaskMethodBuilder1.StateMachineBox1.System.Threading.Tasks.Sources.IValueTaskSource.GetResult(Int16 token)
at Npgsql.NpgsqlBinaryImporter.Complete(Boolean async, CancellationToken cancellationToken)
at Npgsql.NpgsqlBinaryImporter.Complete()
2
at EFCore.BulkExtensions.SqlAdapters.PostgreSql.PostgreSqlAdapter.InsertAsync[T](DbContext context, IEnumerable1 entities, TableInfo tableInfo, Action1 progress, Boolean isAsync, CancellationToken cancellationToken)
at EFCore.BulkExtensions.SqlAdapters.PostgreSql.PostgreSqlAdapter.Insert[T](DbContext context, Type type, IEnumerable1 entities, TableInfo tableInfo, Action1 progress)
at EFCore.BulkExtensions.SqlBulkOperation.Insert[T](DbContext context, Type type, IEnumerable1 entities, TableInfo tableInfo, Action1 progress)
at EFCore.BulkExtensions.DbContextBulkTransaction.Execute[T](DbContext context, Type type, IEnumerable1 entities, OperationType operationType, BulkConfig bulkConfig, Action1 progress)
at EFCore.BulkExtensions.DbContextBulkExtensions.BulkInsert[T](DbContext context, IEnumerable1 entities, BulkConfig bulkConfig, Action1 progress, Type type)
at LookingGlass.System.lgImport.TestIdentityInsert() in /Volumes/LaCie-Data/LookingGlass/Code/LookingGlass.System/lgImport.cs:line 554
Exception data:
Severity: ERROR
SqlState: 23505
MessageText: duplicate key value violates unique constraint "Test_pKey"
Detail: Key (id)=(0) already exists.
Where: COPY Test, line 2
SchemaName: Finance
TableName: Test
ConstraintName: Test_pKey
File: nbtinsert.c
Line: 666
Routine: _bt_check_unique

For testing purposes, here is the definition of the 'Test' table.

DROP TABLE IF EXISTS "Finance"."Test";

CREATE TABLE IF NOT EXISTS "Finance"."Test"
(
id integer NOT NULL GENERATED ALWAYS AS IDENTITY ( INCREMENT 1 START 1 MINVALUE 1 MAXVALUE 2147483647 CACHE 1 ),
val text COLLATE pg_catalog."default",
CONSTRAINT "Test_pKey" PRIMARY KEY (id)
)

TABLESPACE pg_default;

ALTER TABLE IF EXISTS "Finance"."Test"
OWNER to jloper;

COMMENT ON TABLE "Finance"."Test"
IS 'Testing Bulk Insert';

For testing purposes, here is the code that reproduces this issue. We never get to the success line. Always hits the catch/exception.

public void TestIdentityInsert()
{

    using var context = new TestContext();
    try
    {
        var itmLst = new List<Test>();
        itmLst.Add(new Test() { val = "Foo1" });
        itmLst.Add(new Test() { val = "Bar2" });
        context.BulkInsert(itmLst);
        Console.WriteLine("2 rows were inserted");
    }
    catch (Exception e)
    {
        Console.WriteLine(e.ToString());
    }
}

[JPL-1]

I have found a work around.

        context.BulkInsert(itmLst, cfg => cfg.PropertiesToExclude = new List<string> { nameof(Test.id) });

If I specifically tell the library to Exclude the id column, then it works.