add json as string example test (#246)

* add json as string example test

* fix test for older ch

test/ch/connection_test.exs

@@ -582,6 +582,48 @@ defmodule Ch.ConnectionTest do
       assert_raise ArgumentError, fn -> Ch.query!(conn, "SELECT o FROM json") end
     end
 
+    test "json as string", %{conn: conn} do
+      # after v25 ClickHouse started rendering numbers in JSON as strings
+      [[version]] = Ch.query!(conn, "select version()").rows
+      numbers_as_strings? = version >= "25"
+
+      [expected1, expected2] =
+        if numbers_as_strings? do
+          [
+            [[~s|{"answer":"42"}|]],
+            [[~s|{"a":"42"}|], [~s|{"b":"10"}|]]
+          ]
+        else
+          [
+            [[~s|{"answer":42}|]],
+            [[~s|{"a":"42"}|], [~s|{"b":"10"}|]]
+          ]
+        end
+
+      assert Ch.query!(conn, ~s|select '{"answer":42}'::JSON::String|, [],
+               settings: [enable_json_type: 1]
+             ).rows == expected1
+
+      Ch.query!(conn, "CREATE TABLE test_json_as_string(json JSON) ENGINE = Memory", [],
+        settings: [enable_json_type: 1]
+      )
+
+      Ch.query!(
+        conn,
+        "INSERT INTO test_json_as_string(json) FORMAT RowBinary",
+        _rows = [[Jason.encode_to_iodata!(%{"a" => 42})], [Jason.encode_to_iodata!(%{"b" => 10})]],
+        types: [:string],
+        settings: [
+          enable_json_type: 1,
+          input_format_binary_read_json_as_string: 1
+        ]
+      )
+
+      assert Ch.query!(conn, "select json::String from test_json_as_string", [],
+               settings: [enable_json_type: 1]
+             ).rows == expected2
+    end
+
     # TODO enum16
 
     test "enum8", %{conn: conn} do