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A toolkit for data mapping and language integrated query for Elixir
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lib/ecto/query/builder/join.ex
defmodule Ecto.Query.Builder.Join do
@moduledoc false
alias Ecto.Query.Builder
alias Ecto.Query.JoinExpr
@doc """
Escapes a join expression (not including the `on` expression).
It returns a tuple containing the binds, the on expression (if available)
and the association expression.
## Examples
iex> escape(quote(do: x in "foo"), [])
{:x, {"foo", nil}, nil}
iex> escape(quote(do: "foo"), [])
{:_, {"foo", nil}, nil}
iex> escape(quote(do: x in Sample), [])
{:x, {nil, {:__aliases__, [alias: false], [:Sample]}}, nil}
iex> escape(quote(do: x in {"foo", Sample}), [])
{:x, {"foo", {:__aliases__, [alias: false], [:Sample]}}, nil}
iex> escape(quote(do: x in {"foo", :sample}), [])
{:x, {"foo", :sample}, nil}
iex> escape(quote(do: c in assoc(p, :comments)), [p: 0])
{:c, nil, {0, :comments}}
"""
@spec escape(Macro.t, Keyword.t) :: {[atom], Macro.t | nil, Macro.t | nil}
def escape({:in, _, [{var, _, context}, expr]}, vars)
when is_atom(var) and is_atom(context) do
{_, expr, assoc} = escape(expr, vars)
{var, expr, assoc}
end
def escape({:__aliases__, _, _} = module, _vars) do
{:_, {nil, module}, nil}
end
def escape(string, _vars) when is_binary(string) do
{:_, {string, nil}, nil}
end
def escape({string, {:__aliases__, _, _} = module}, _vars) when is_binary(string) do
{:_, {string, module}, nil}
end
def escape({string, atom}, _vars) when is_binary(string) and is_atom(atom) do
{:_, {string, atom}, nil}
end
def escape({:assoc, _, [{var, _, context}, field]}, vars)
when is_atom(var) and is_atom(context) do
var = Builder.find_var!(var, vars)
field = Builder.quoted_field!(field)
{:_, nil, {var, field}}
end
def escape({:^, _, [expr]}, _vars) do
{:_, quote(do: Ecto.Query.Builder.Join.join!(unquote(expr))), nil}
end
def escape(join, _vars) do
Builder.error! "malformed join `#{Macro.to_string(join)}` in query expression"
end
@doc """
Called at runtime to check dynamic joins.
"""
def join!(expr) when is_atom(expr),
do: {nil, expr}
def join!(expr) when is_binary(expr),
do: {expr, nil}
def join!({source, module}) when is_binary(source) and is_atom(module),
do: {source, module}
def join!(expr),
do: Builder.error!("expected join to be a string, atom or {string, atom}, got: `#{inspect expr}`")
@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, atom, [Macro.t], Macro.t, Macro.t, Macro.t, Macro.Env.t) :: {Macro.t, Keyword.t, non_neg_integer | nil}
def build(query, qual, binding, expr, on, count_bind, env) do
binding = Builder.escape_binding(binding)
{join_bind, join_expr, join_assoc} = escape(expr, binding)
qual = validate_qual(qual)
validate_bind(join_bind, binding)
if join_bind != :_ and !count_bind do
# If count_bind is not an integer, make it a variable.
# The variable is the getter/setter storage.
count_bind = quote(do: count_bind)
count_setter = quote(do: unquote(count_bind) = Builder.count_binds(query))
end
if on && join_assoc do
Builder.error! "cannot specify `on` on `#{qual}_join` when using association join, " <>
"add extra clauses with `where` instead"
end
binding = binding ++ [{join_bind, count_bind}]
join_on = escape_on(on || true, binding, env)
join =
quote do
%JoinExpr{qual: unquote(qual), source: unquote(join_expr),
on: unquote(join_on), assoc: unquote(join_assoc),
file: unquote(env.file), line: unquote(env.line)}
end
if is_integer(count_bind) do
count_bind = count_bind + 1
quoted = Builder.apply_query(query, __MODULE__, [join], env)
else
count_bind = quote(do: unquote(count_bind) + 1)
quoted =
quote do
query = Ecto.Queryable.to_query(unquote(query))
unquote(count_setter)
%{query | joins: query.joins ++ [unquote(join)]}
end
end
{quoted, binding, count_bind}
end
def apply(query, expr) do
query = Ecto.Queryable.to_query(query)
%{query | joins: query.joins ++ [expr]}
end
defp escape_on(on, binding, env) do
{on, params} = Builder.escape(on, :boolean, %{}, binding, env)
params = Builder.escape_params(params)
quote do: %Ecto.Query.QueryExpr{
expr: unquote(on),
params: unquote(params),
line: unquote(env.line),
file: unquote(env.file)}
end
defp validate_qual(qual) when is_atom(qual) do
qual!(qual)
end
defp validate_qual(qual) do
quote(do: Ecto.Query.Builder.Join.qual!(unquote(qual)))
end
defp validate_bind(bind, all) do
if bind != :_ and bind in all do
Builder.error! "variable `#{bind}` is already defined in query"
end
end
@qualifiers [:inner, :left, :right, :full]
@doc """
Called at runtime to check dynamic qualifier.
"""
def qual!(qual) when qual in @qualifiers, do: qual
def qual!(qual) do
Builder.error! "invalid join qualifier `#{inspect qual}`, accepted qualifiers are: " <>
Enum.map_join(@qualifiers, ", ", &"`#{inspect &1}`")
end
end