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A toolkit for data mapping and language integrated query for Elixir
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lib/ecto/query/from_builder.ex
defmodule Ecto.Query.FromBuilder do
@moduledoc false
alias Ecto.Query.BuilderUtil
@doc """
Handles from expressions.
The expressions may either contain an `in` expression or not.
The right side is always expected to Queryable.
## Examples
iex> escape(quote do: MyModel)
{[], quote(do: MyModel)}
iex> escape(quote do: p in posts)
{[p: 0], quote(do: posts)}
iex> escape(quote do: [p, q] in posts)
{[p: 0, q: 1], quote(do: posts)}
iex> escape(quote do: [_, _] in abc)
{[], quote(do: abc)}
iex> escape(quote do: other)
{[], quote(do: other)}
iex> escape(quote do: x() in other)
** (Ecto.QueryError) invalid `from` query expression
"""
@spec escape(Macro.t) :: {Keyword.t, Macro.t}
def escape({:in, _, [list, expr]}) when is_list(list) do
binds =
Enum.flat_map(Stream.with_index(list), fn
{{:_, _, context}, _ix} when is_atom(context) ->
[]
{{var, _, context}, ix} when is_atom(var) and is_atom(context) ->
[{var, ix}]
{_, _count} ->
raise Ecto.QueryError, reason: "invalid `from` query expression"
end)
{binds, expr}
end
def escape({:in, meta, [var, expr]}) do
escape({:in, meta, [[var], expr]})
end
def escape(expr) do
{[], expr}
end
@doc """
Builds a quoted expression.
The quoted expression should evaluate to a query at runtime.
If possible, it does all calculations at compile time to avoid
runtime work.
"""
@spec build_with_binds(Macro.t, Macro.Env.t) :: {Macro.t, Keyword.t, non_neg_integer | nil}
def build_with_binds(expr, env) do
{binds, expr} = escape(expr)
case Macro.expand(expr, env) do
atom when is_atom(atom) ->
count_bind = 1
if Code.ensure_compiled?(atom) do
quoted = Ecto.Queryable.to_query(atom) |> Macro.escape
else
quoted = atom
end
other ->
count_bind = nil
quoted = other
end
quoted = BuilderUtil.apply_query(quoted, __MODULE__, [length(binds)], env)
{quoted, binds, count_bind}
end
@doc """
The callback applied by `build_with_binds/2` to build the query.
"""
@spec apply(Ecto.Queryable.t, non_neg_integer) :: Ecto.Query.t
def apply(query, binds) do
query = Ecto.Queryable.to_query(query)
check_binds(query, binds)
query
end
defp check_binds(query, count) do
if count > 1 and count > BuilderUtil.count_binds(query) do
raise Ecto.QueryError,
reason: "`from` in query expression specified #{count} " <>
"binds but query contains #{BuilderUtil.count_binds(query)} binds"
end
end
end