t is not a real variable, because where is not a function, it’s a macro. t is part of the syntax of the macro. Examples here: https://hexdocs.pm/ecto/Ecto.Query.html#where/3-expressions-example

The where macro basically just creates a t that you can use in the second part of where.

Yes. If you pipe a query struct into where, it grabs the schema you’re querying out of the query and makes it available as whatever variable you put in the list.

Final version using the advice from @benwilson512

def list_items(%{matching: name}) when is_binary(name) do
    Item
    # |> where([m], ilike(m.name, ^"%#{name}%"))
    |> search(name)
    |> Repo.all()
  end

  defp search(query, name) do
    query
    |> where([t], ilike(t.name, ^"%#{name}%"))
  end

You’re overthinking my response, I’m saying you literally can just leave out the from:

  defp search(query, name) do
    query
    |> where([t], ilike(t.name, ^"%#{name}%"))
  end

    term
    |> from t in Item

This isn’t a valid way to use from, it expands to from(term, t in Item) since |> puts arguments at the front.