How to restart postgres sequence with Entity framework seeding migration? - postgresql

Question

I have the following database seeder:
public partial class Seed_Languages : Migration
{
protected override void Up(MigrationBuilder migrationBuilder)
{
migrationBuilder.InsertData(
table: "Languages",
columns: new[] { "LanguageId", "LangCode", "LangName", "Sort" },
values: new object[,]
{
{ 1, "AU", "Австралия", 0 },
{ 159, "CX", "Остров Рождества", 0 },
{ 160, "PN", "Острова Питкэрн", 0 },
{ 161, "SH", "Острова Святой Елены, Вознесения и Тристан-да-Кунья", 0 },
{ 162, "PK", "Пакистан", 0 },
{ 163, "PW", "Палау", 0 },
.... and so on ...
As you can see I'm going to populate some table, that contains language's names (on Russian, for showing on UI), language's codes, some additional field - Sort (not important here) and primary key. Simple, right?
Here is the table:
Then I create it inside my OnModelCreating:
protected override void OnModelCreating(ModelBuilder modelBuilder)
{
base.OnModelCreating(modelBuilder);
// many fluent api calls
LanguagesSeeder.SeedLanguages(modelBuilder);
}
Then I run $ dotnet ef database update and seeding works fine! But problems soon began.
When I try to insert new one language, .NET gives me:
Exception data:
Severity: ERROR
SqlState: 23505
MessageText: duplicate key value violates unique constraint "PK_Languages"
Detail: Key ("LanguageId")=(1) already exists.
SchemaName: public
TableName: Languages
ConstraintName: PK_Languages
File: nbtinsert.c
Line: 434
"Hmmmm lets try again" - I thought. And:
Exception data:
Severity: ERROR
SqlState: 23505
MessageText: duplicate key value violates unique constraint "PK_Languages"
Detail: Key ("LanguageId")=(2) already exists.
SchemaName: public
TableName: Languages
ConstraintName: PK_Languages
File: nbtinsert.c
Line: 434
Routine: _bt_check_unique
You see that? The same error but with another Primary key complaint! The first was: Key ("LanguageId")=(1) already exists. and the second Key ("LanguageId")=(2) already exists.
!
So, what to do? I know this way:
ALTER SEQUENCE <name of sequence> RESTART WITH <your number is here>;
But it's pretty uncomfortable to run this SQL in a console after seeding. Am I miss something? Maybe, there is a standard way for this, I mean using some EF API?
Update
I will show you my Language model:
namespace Domains
{
public class Language
{
public int LanguageId { get; set; }
public int Sort { get; set; }
public List<Customer> Customers { get; set; }
public List<PushMessageLang> PushMessageLangs { get; set; }
[NotMapped]
public IEnumerable<PushMessage> PushMessages
{
get => PushMessageLangs?.Select(r => r.PushMessage);
set => PushMessageLangs = value.Select(v => new PushMessageLang()
{
PushMessageId = v.PushMessageId
}).ToList();
}
public string LangName { get; set; }
public string LangCode { get; set; }
}
}
I make insert via my repository abstraction:
Base repository:
public class BaseRepository<T, C> : IRepository<T>
where T : class
where C : DbContext
{
protected C DataContext;
private readonly DbSet<T> _dbset;
public BaseRepository(C context)
{
DataContext = context;
_dbset = context.Set<T>();
}
public virtual IQueryable<T> All => _dbset;
public virtual async Task SaveAsync(T entity)
{
await _dbset.AddAsync(entity);
await DataContext.SaveChangesAsync();
}
public async Task SaveAsync(List<T> entity)
{
await _dbset.AddRangeAsync(entity);
await DataContext.SaveChangesAsync();
}
public virtual async Task UpdateAsync(T entity)
{
_dbset.Attach(entity).State = EntityState.Modified;
_dbset.Update(entity);
await DataContext.SaveChangesAsync();
}
public virtual async Task DeleteAsync(int id)
{
var dbEntity = await _dbset.FindAsync(id);
if (dbEntity != null)
{
_dbset.Remove(dbEntity);
await DataContext.SaveChangesAsync();
}
}
}
And in the controller:
public async Task<IActionResult> Create([FromForm] LanguageViewModel viewModel)
{
if (!ModelState.IsValid)
{
return View(viewModel);
}
var newLanguage = new Language()
{
Sort = viewModel.Sort,
LangCode = viewModel.Code,
LangName = viewModel.Name
};
await _languageRepository.SaveAsync(newLanguage);
return RedirectToAction("Index");
}
Update 2
As asked in the comments I'll pin here all fluent api for Language model:
// many to many with `Message` entity
modelBuilder.Entity<PushMessageLang>()
.HasKey(bc => new { bc.PushLangId, bc.PushMessageId });
modelBuilder.Entity<PushMessageLang>()
.HasOne(bc => bc.Language)
.WithMany(b => b.PushMessageLangs)
.HasForeignKey(bc => bc.PushLangId)
.OnDelete(DeleteBehavior.Cascade);
modelBuilder.Entity<PushMessageLang>()
.HasOne(bc => bc.PushMessage)
.WithMany(c => c.PushMessageLangs)
.HasForeignKey(bc => bc.PushMessageId)
.OnDelete(DeleteBehavior.Cascade);
// has unique language code
modelBuilder.Entity<Language>()
.HasIndex(x => x.LangCode).IsUnique();
Update 3
As asked #Roman Marusyk, I pine here SQL script for creating Languages table.
-- auto-generated definition
create table "Languages"
(
"LanguageId" integer generated by default as identity
constraint "PK_Languages"
primary key,
"LangName" text,
"LangCode" text,
"Sort" integer default 0 not null
);
alter table "Languages"
owner to makeapp_pushes;
create unique index "IX_Languages_LangCode"
on "Languages" ("LangCode");
Hmm, now I see that don't have anything about auto increment.
But my SQL client shows my:

Answer 1

Add HasKey to model configuration
modelBuilder.Entity<Language>()
.HasKey(x => x.LanguageId)
.HasIndex(x => x.LangCode).IsUnique();
as #IvanStoev mentioned, by convention, the property LanguageId is already the primary key
Try to specify
modelBuilder.Entity<Language>()
.Property(p => p.LanguageId)
.ValueGeneratedOnAdd();

Answer 2

In the migration I have added manually this string:
migrationBuilder.RestartSequence("Languages_LanguageId_seq", 251, "public");
where Languages_LanguageId_seq - name of sequence,
251 - number of starting of the sequence (PK value),
public - scheme name.
Here is documentation. Now I can insert without any errors.