docs(ds): Update documentation for the storage layouts

apps/emqx/src/emqx_ds_schema.erl

@@ -246,7 +246,8 @@ fields(layout_builtin_reference) ->
                 reference,
                 #{
                     'readOnly' => true,
-                    importance => ?IMPORTANCE_LOW
+                    importance => ?IMPORTANCE_LOW,
+                    desc => ?DESC(layout_builtin_reference_type)
                 }
             )}
     ].
@@ -257,6 +258,8 @@ desc(builtin_local_write_buffer) ->
     ?DESC(builtin_local_write_buffer);
 desc(layout_builtin_wildcard_optimized) ->
     ?DESC(layout_builtin_wildcard_optimized);
+desc(layout_builtin_reference) ->
+    ?DESC(layout_builtin_reference);
 desc(_) ->
     undefined.
 

rel/i18n/emqx_ds_schema.hocon

@@ -90,11 +90,20 @@ wildcard_optimized_epoch_bits.desc:
 
   Time span covered by each epoch grows exponentially with the value of `epoch_bits`:
 
-  - `epoch_bits = 1`: epoch time = 1 millisecond
+  - `epoch_bits = 1`: epoch time = 2 microseconds
-  - `epoch_bits = 2`: 2 milliseconds
+  - `epoch_bits = 2`: 4 microseconds
   ...
-  - `epoch_bits = 10`: 1024 milliseconds
+  - `epoch_bits = 20`: ~1s
-  - `epoch_bits = 13`: ~8 seconds
   ...~"""
 
+layout_builtin_reference.label: "Reference layout"
+layout_builtin_reference.desc:
+  """~
+  A simplistic layout type that stores all messages from all topics in chronological order in a single stream.
+
+  Not recommended for production use.~"""
+
+layout_builtin_reference_type.label: "Layout type"
+layout_builtin_reference_type.desc: "Reference layout type."
+
 }