Lotus.Source.Adapters.Ecto.SQL.FilterInjector (Lotus v1.0.0)

Shared helpers for SQL-based sources to inject filter conditions into queries.

Wraps the original query in a CTE and appends WHERE clauses using parameterized queries. Each SQL source calls this with its own quote_fn and placeholder_fn for database-specific identifier quoting and parameter placeholders.

Example

quote_fn = fn id -> ~s("#{id}") end
placeholder_fn = fn idx -> "$#{idx}" end
Lotus.Source.Adapters.Ecto.SQL.FilterInjector.apply("SELECT * FROM users", [25], [
  %Lotus.Query.Filter{column: "region", op: :eq, value: "US"}
], quote_fn, placeholder_fn)
#=> {~s(WITH _base AS (SELECT * FROM users) SELECT * FROM _base WHERE "region" = $2), [25, "US"]}

Summary

Functions

apply(sql, params, filters, quote_fn, placeholder_fn)

Wraps the given SQL in a CTE and appends parameterized WHERE clauses for each filter.

Functions

apply(sql, params, filters, quote_fn, placeholder_fn)

@spec apply(
  String.t(),
  list(),
  [Lotus.Query.Filter.t()],
  (String.t() -> String.t()),
  (pos_integer() ->
     String.t())
) ::
  {String.t(), list()}

Wraps the given SQL in a CTE and appends parameterized WHERE clauses for each filter.

quote_fn is a 1-arity function that quotes an identifier for the target database. placeholder_fn is a 1-arity function that takes a 1-based parameter index and returns the placeholder string (e.g., "$1" for Postgres, "?" for MySQL).

Returns {sql, params} where params is the updated parameter list with filter values appended. Returns {sql, params} unchanged if filters is empty.