+<h2>XAPIAN FIELD PROCESSORS</h2>
+<pre>
+ Certain optional features of the notmuch query processor rely on the
+ presence of the Xapian field processor API. You can determine if your
+ notmuch was built against a sufficiently recent version of Xapian by
+ running
+
+ % notmuch config get built_with.field_processor
+
+ Currently the following features require field processor support:
+
+ · non-range date queries, e.g. "date:today"
+
+ · named queries e.g. "query:my_special_query"
+
+ · regular expression searches, e.g. "subject:/^\[SPAM\]/"
+</pre>
+