Installation

The package can be installed by adding sqlcommenter to your list of dependencies in mix.exs:

def deps do
  [
    {:sqlcommenter, "~> 0.1.0"}
  ]
end

Sqlcommenter

Disclaimer: Currently using comments disables prepared statements and may increase cpu load on your database. Elixir implementation of sqlcommenter escaping. Attach SQL comments to correlate user code in ORMs and SQL drivers with SQL statements.

Usage

Add these callbacks to your Repo module, adjust to your needs. The stacktrace option is only required when you plan to include use the extract_repo_caller function. This function also accepts the MODULE as the second argument to exclude it from the stacktrace.

The sqlcommenter option is used for adding static data to the comment like the running app, team, owner etc. Any dynamic data can be added in the prepare_query function. Besides the caller it can also add the trace and span.

The generated comment needs to be added as comment option - this will be passed to the adapter.

def default_options(_operation) do
  [stacktrace: true, prepare: :unnamed, sqlcommenter: [team: "sqlcomm", app: "sqlcomm"]]
end

def prepare_query(_operation, query, opts) do
  sqlcommennter_defaults = Keyword.get(opts, :sqlcommenter)
  caller = Sqlcommenter.extract_repo_caller(opts, __MODULE__)
  comment = Sqlcommenter.to_str([caller: caller] ++ sqlcommenter_defaults)

  {query, [comment: comment] ++ opts}
end

Now your postgres logs should look will return a log line like this:

2024-10-27 21:43:04.331 GMT,"postgres","sqlcomm_test",416336,"127.0.0.1:53348",671eb3e8.65a50,6, "SELECT",2024-10-27 21:43:04 GMT,15/54,61620,LOG,00000,"execute <unnamed>: SELECT u0.""id"",
u0.""active"", u0.""name"", u0.""inserted_at"", u0.""updated_at"" FROM ""users"" AS
u0/*app='sqlcomm',caller='Elixir.SqlcommTest.test%20insert%20user%2F1',team='sqlcomm'*/"
,,,,,,,,,"","client backend",,0

Alternatively, when you're concerned about performance and your options are mostly static you can also omit the Sqlcommenter logic and write your own custom function. Just remember that according the sqlcommenter specs the keys must be sorted, and the values properly escaped check specification and sqlcommenter source code.

defmodule SqlEEx do
   require EEx

  EEx.function_from_string(
    :def,
    :to_comment,
    "app:'sqlcomm',caller:'<%= caller %>'team:'sqlcomm'",
    [:caller]
  )
end

And then use it in your repo:

def prepare_query(_operation, query, opts) do
  caller = Sqlcommenter.extract_repo_caller(opts, __MODULE__)
  SqlEEx.to_comment(caller: caller)
  {query, [comment: comment] ++ opts}
end

Documentation can be generated with ExDoc and published on HexDocs. Once published, the docs can be found at https://hexdocs.pm/sqlcommenter.