A protocol to print various data structures as valid SQL expressions.

to_expression/1 is the main function and to_string_literal/1 is an optional helper for it.

Ecto.DevLogger tries to represent complex terms, like arrays (lists) and composite types (tuples) as string literal first. Not all terms are easy/efficient/whatever to represent as strings, so if to_string_literal/1 returns a string for all elements inside the array, then array will be represented as string as well. Otherwise, array will be represented using ARRAY constructor:

iex> Ecto.DevLogger.PrintableParameter.to_expression(["Elixir", "Ecto"])
"'{Elixir,Ecto}'"

iex> Ecto.DevLogger.PrintableParameter.to_expression(["Elixir", "Ecto", <<153>>])
"ARRAY['Elixir','Ecto',DECODE('mQ==','BASE64')]"

The same is true for composite types (tuples):

iex> Ecto.DevLogger.PrintableParameter.to_expression({"Elixir", "Ecto"})
"'(Elixir,Ecto)'"

iex> Ecto.DevLogger.PrintableParameter.to_expression({"Elixir", "Ecto", <<153>>})
"ROW('Elixir','Ecto',DECODE('mQ==','BASE64'))"