Remove JSON format as to not directly depend on Jason

Author: josevalim

integration_test/pg/explain_test.exs

@@ -27,14 +27,6 @@ defmodule Ecto.Integration.ExplainTest do
     end)
   end
 
-  test "explain JSON format" do
-    [explain] = TestRepo.explain(:all, Post, analyze: true, verbose: true, timeout: 20000, format: :json) |> Jason.decode!()
-    keys = explain["Plan"] |> Map.keys
-    assert Enum.member?(keys, "Actual Loops")
-    assert Enum.member?(keys, "Actual Rows")
-    assert Enum.member?(keys, "Actual Startup Time")
-  end
-
   test "explain MAP format" do
     [explain] = TestRepo.explain(:all, Post, analyze: true, verbose: true, timeout: 20000, format: :map)
     keys = explain["Plan"] |> Map.keys

lib/ecto/adapters/postgres/connection.ex

@@ -255,15 +255,9 @@ if Code.ensure_loaded?(Postgrex) do
       {explain_opts, opts} =
         Keyword.split(opts, ~w[analyze verbose costs settings buffers timing summary format]a)
 
-      json_format? = {:format, :json} in explain_opts
       map_format? = {:format, :map} in explain_opts
 
       case query(conn, build_explain_query(query, explain_opts), params, opts) do
-        {:ok, %Postgrex.Result{rows: rows}} when json_format? ->
-          case Jason.encode(List.flatten(rows)) do
-            {:ok, json} -> {:ok, json}
-            {:error, error} -> error
-          end
         {:ok, %Postgrex.Result{rows: rows}} when map_format? ->
           {:ok, List.flatten(rows)}
         {:ok, %Postgrex.Result{rows: rows}} ->
@@ -1244,7 +1238,6 @@ if Code.ensure_loaded?(Postgrex) do
     defp quote_boolean(value), do: error!(nil, "bad boolean value #{value}")
 
     defp format_to_sql(:text), do: "FORMAT TEXT"
-    defp format_to_sql(:json), do: "FORMAT JSON"
     defp format_to_sql(:map), do: "FORMAT JSON"
     defp format_to_sql(:yaml), do: "FORMAT YAML"
 

lib/ecto/adapters/sql.ex

@@ -281,7 +281,9 @@ defmodule Ecto.Adapters.SQL do
 
   Also note that:
 
-    * Currently `:json`, `:map`, `:yaml` and `:text` format options are supported for PostgreSQL
+    * Currently `:map`, `:yaml`, and `:text` format options are supported
+      for PostgreSQL. `:map` is the deserialized JSON encoding. The last two
+      options return the result as a string.
     * Any other value passed to `opts` will be forwarded to the underlying
       adapter query function, including Repo shared options such as `:timeout`;
     * Non built-in adapters may have specific behavior and you should consult