Обсуждение: does postgresql 10 have something similar to sql server's set identity_insert

john snow wrote:
> to temporarily allow explicit values to be inserted into the identity column of a table
> to facilitate the generation of test data from application code?
> 
> using sql, i know it's possible to issue INSERTs with OVERRIDING SYSTEM VALUE clause to fill
> identity columns with user-specified values. but i'm using an ORM (object-relation mapper)
> Framework from Microsoft (Entity Framework Core 2.1)  and a C# test data generator library,
> and i'm generating "data aggregates" that have foreign key relationships so it would be a
> great convenience if I could save test data with known primary and foreign key values to
> the database as this would make it easier for me to make assertions about my data.
> 
> ideally, i'm looking for something like this:
> 
> myDbContext.Database.ExecuteSqlCommand("...");  //ask postgresql to allow explicit id values
> for inserts from here on
> var testData = CreateTestData();
> myDbContext.MyEntity.AddRange(testData);
> myDbContext.SaveChanges();

You could create the identity column as

  GENERATED BY DEFAULT AS IDENTITY

Then you simply insert DEFAULT for this column when you
want the generated value (or you don't specify the column
in the INSERT statement).

Yours,
Laurenz Albe
-- 
Cybertec | https://www.cybertec-postgresql.com

john snow schrieb am 31.05.2018 um 11:15:
> to temporarily allow explicit values to be inserted into the identity
> column of a table to facilitate the generation of test data from
> application code?
> 
> using sql, i know it's possible to issue INSERTs with OVERRIDING
> SYSTEM VALUE clause to fill identity columns with user-specified
> values. but i'm using an ORM (object-relation mapper) Framework from
> Microsoft (Entity Framework Core 2.1)  and a C# test data generator
> library, and i'm generating "data aggregates" that have foreign key
> relationships so it would be a great convenience if I could save test
> data with known primary and foreign key values to the database as
> this would make it easier for me to make assertions about my data.
> 
> ideally, i'm looking for something like this:
> 
> myDbContext.Database.ExecuteSqlCommand("...");  //ask postgresql to allow explicit id values for inserts from here
on
> var testData = CreateTestData();
> myDbContext.MyEntity.AddRange(testData);
> myDbContext.SaveChanges();
> 

If you use a serial or identity column you can just insert your rows.
There is no need to "turn on" (or off) anything.

But you _have_ to synchronize the underlying sequence after you do that:

    select setval(pg_get_serial_sequence('the_table', 'id'), (select max(id) from the_table));

Thomas