?_trace=1 now depends on trace_debug setting, closes #1359

docs/json_api.rst

@@ -206,6 +206,16 @@ query string arguments:
     For how many seconds should this response be cached by HTTP proxies? Use
     ``?_ttl=0`` to disable HTTP caching entirely for this request.
 
+``?_trace=1``
+    Turns on tracing for this page: SQL queries executed during the request will
+    be gathered and included in the response, either in a new ``"_traces"`` key
+    for JSON responses or at the bottom of the page if the response is in HTML.
+
+    The structure of the data returned here should be considered highly unstable
+    and very likely to change.
+
+    Only available if the :ref:`setting_trace_debug` setting is enabled.
+
 .. _table_arguments:
 
 Table arguments
@@ -389,14 +399,6 @@ Special table arguments
 ``?_nocount=1``
     Disable the ``select count(*)`` query used on this page - a count of ``None`` will be returned instead.
 
-``?_trace=1``
-    Turns on tracing for this page: SQL queries executed during the request will
-    be gathered and included in the response, either in a new ``"_traces"`` key
-    for JSON responses or at the bottom of the page if the response is in HTML.
-
-    The structure of the data returned here should be considered highly unstable
-    and very likely to change.
-
 .. _expand_foreign_keys:
 
 Expanding foreign key references

docs/settings.rst

@@ -286,6 +286,22 @@ Some examples:
 * https://latest.datasette.io/fixtures?_context=1
 * https://latest.datasette.io/fixtures/roadside_attractions?_context=1
 
+.. _setting_trace_debug:
+
+trace_debug
+~~~~~~~~~~~
+
+This setting enables appending ``?_trace=1`` to any page in order to see the SQL queries and other trace information that was used to generate that page.
+
+Enable it like this::
+
+    datasette mydatabase.db --setting trace_debug 1
+
+Some examples:
+
+* https://latest.datasette.io/?_trace=1
+* https://latest.datasette.io/fixtures/roadside_attractions?_trace=1
+
 .. _setting_base_url:
 
 base_url