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A toolkit for data mapping and language integrated query for Elixir
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lib/ecto/query/builder/from.ex
defmodule Ecto.Query.Builder.From do
@moduledoc false
alias Ecto.Query.Builder
@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 in {"posts", MyModel})
{[p: 0], quote(do: {"posts", MyModel})}
iex> escape(quote do: [p, q] in posts)
{[p: 0, q: 1], quote(do: posts)}
iex> escape(quote do: [_, _] in abc)
{[_: 0, _: 1], quote(do: abc)}
iex> escape(quote do: other)
{[], quote(do: other)}
iex> escape(quote do: x() in other)
** (Ecto.Query.CompileError) binding list should contain only variables, got: x()
"""
@spec escape(Macro.t) :: {Keyword.t, Macro.t}
def escape({:in, _, [var, expr]}) do
{Builder.escape_binding(List.wrap(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(Macro.t, Macro.Env.t) :: {Macro.t, Keyword.t, non_neg_integer | nil}
def build(expr, env) do
{binds, expr} = escape(expr)
{count_bind, quoted} =
case Macro.expand(expr, env) do
schema when is_atom(schema) ->
# Get the source at runtime so no unnecessary compile time
# dependencies between modules are added
source = quote do: unquote(schema).__schema__(:source)
prefix = quote do: unquote(schema).__schema__(:prefix)
{1, query(prefix, source, schema)}
source when is_binary(source) ->
# When a binary is used, there is no schema
{1, query(nil, source, nil)}
{source, schema} when is_binary(source) ->
prefix = quote do: unquote(schema).__schema__(:prefix)
{1, query(prefix, source, schema)}
other ->
{nil, other}
end
quoted = Builder.apply_query(quoted, __MODULE__, [length(binds)], env)
{quoted, binds, count_bind}
end
defp query(prefix, source, schema) do
{:%, [], [Ecto.Query, {:%{}, [], [from: {source, schema}, prefix: prefix]}]}
end
@doc """
The callback applied by `build/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 > Builder.count_binds(query) do
Builder.error! "`from` in query expression specified #{count} " <>
"binds but query contains #{Builder.count_binds(query)} binds"
end
end
end