Added docs for search operators

docs/topics/search/searching.rst

@@ -85,6 +85,49 @@ This can be limited to a certian set of fields using the ``fields`` keyword argu
     [<EventPage: Event 1>, <EventPage: Event 2>]
 
 
+Changing search behaviour
+-------------------------
+
+Search operator
+^^^^^^^^^^^^^^^
+
+.. versionadded:: 1.2
+
+The search operator specifies how search should behave when the user has typed in multiple search terms. There are two possible values:
+
+ - "or" - The results must match at least one term (default for Elasticsearch)
+ - "and" - The results must match all terms (default for database search)
+
+Both operators have benefits and drawbacks. The "or" operator will return many more results but will likely contain a lot of results that aren't relevent. The "and" operator only returns results that contain all search terms, but require the user to be more precise with their query.
+
+We recommend using the "or" operator when ordering by relevance and the "and" operator when ordering by anything else (note: the database backend doesn't currently support ordering by relevance).
+
+Here's an example of using the "operator" keyword argument:
+
+.. code-block:: python
+
+    # The database contains a "Thing" model with the following items:
+    # - Hello world
+    # - Hello
+    # - World
+
+
+    # Search with the "or" operator
+    >>> s = get_search_backend()
+    >>> s.search("Hello world", Things, operator="or")
+
+    # All records returned as they all contain either "hello" or "world"
+    [<Thing: Hello World>, <Thing: Hello>, <Thing: World>]
+
+
+    # Search with the "and" operator
+    >>> s = get_search_backend()
+    >>> s.search("Hello world", Things, operator="and")
+
+    # Only "hello world" returned as that's the only item that contains both terms
+    [<Thing: Hello world>]
+
+
 .. _wagtailsearch_frontend_views: