CODEWITHSUNDEEP
postgresqlelixirectopostgrex
kayne
kayne

Reputation: 349

Get the current ID in Postgres before insert

I'm trying to hash the current ID of every book I insert in the database, so that every book will be recognized by such 'code'.

Is there is a way in Ecto to display value of fragment("nextval('books_id_seq')") in a changeset or Ecto.insert() ?

So far all I can do is get the last id by calling it from this function :

...
  def get_currval() do
    from(b in Book,
      select: fragment("nextval('books_id_seq')"),
      limit: 1
    )
    |> Repo.one
  end

I'd love to have something more reliable, like a fragment in the insert query.

Upvotes: 0

Views: 3612

Answers (1)

icuken
icuken

Reputation: 1356

There is a way to get ID back in the same query: RETURNING, that allows you

# \d+ tmp_play
                                                  Table "pg_temp_11.tmp_play"
 Column |         Type          |                       Modifiers                       | Storage  | Stats target | Description 
--------+-----------------------+-------------------------------------------------------+----------+--------------+-------------
 id     | integer               | not null default nextval('tmp_play_id_seq'::regclass) | plain    |              | 
 name   | character varying(32) |                                                       | extended |              | 
Indexes:
    "tmp_play_pkey" PRIMARY KEY, btree (id)

# INSERT INTO tmp_play (name) VALUES ('Hello') RETURNING id;
 id 
----
  1
(1 row)

INSERT 0 1

# INSERT INTO tmp_play (name) VALUES ('world') RETURNING id;
 id 
----
  2
(1 row)

INSERT 0 1

Upvotes: 0

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