Using Elixir - Ecto for complex queries

Question

So I am in the process of converting a node app into Elixir and have some queries that I would like to use Ecto for but I haven't found a way that works and would like to refrain from concatenating strings and arguments if possible.

I have about 10 queries that are chained within a transaction that look somewhat like this:

INSERT INTO user_servers(user_id, server_id, server_type_code,      position,                 active_flag,   create_date,      created_by)
                 SELECT   ?,         ?,      'SERVER',      (COALESCE(MAX(position), 0) + 1),     'Y',     CURRENT_TIMESTAMP,       ?
                                                                        FROM user_servers WHERE server_type_code = 'SERVER' and user_id = ?;

This is within a transaction.

So my first question is, as I am really struggling figuring out the right combination in ecto to do just this query.

How can I do an INSERT with a SELECT clause in Ecto and be able to replace the question marks with hardcoded items.

I am using snowflake to create ID's so will create those ids server-side and send them through.

My next question is, how can I use Repo.transaction with multi.new with Raw SQL.

Answer 1

I believe you will want to use the raw query/4 API. This will allow you to write a custom query and have the benefit of not needing to escape your input. Something like the following should work.

raw_query = "INSERT INTO user_servers(user_id, server_id, server_type_code, position, active_flag, create_date, created_by)
             SELECT $1, $2, 'SERVER', (COALESCE(MAX(position), 0) + 1), 'Y', CURRENT_TIMESTAMP, $3
             FROM user_servers WHERE server_type_code = 'SERVER' and user_id = $4;"

Ecto.Adapters.SQL.query(MyRepo, raw_query, [value1, value2, value3, value4])