[PATCH 4/4] doc: document thread subqueries

David Bremner david at tethera.net
Sat May 5 09:05:23 PDT 2018

Mention both performance and quoting issues.
 doc/man7/notmuch-search-terms.rst | 26 ++++++++++++++++++++++++--
 1 file changed, 24 insertions(+), 2 deletions(-)

diff --git a/doc/man7/notmuch-search-terms.rst b/doc/man7/notmuch-search-terms.rst
index 248444e3..ec999eed 100644
--- a/doc/man7/notmuch-search-terms.rst
+++ b/doc/man7/notmuch-search-terms.rst
@@ -83,6 +83,22 @@ thread:<thread-id>
     messages). These thread ID values can be seen in the first column
     of output from **notmuch search**
+thread:{<notmuch query>}
+    If notmuch is built with **Xapian Field Processors** (see below),
+    threads may be searched for indirectly by providing an arbitrary
+    notmuch query in **{}**. For example, the following returns
+    threads containing a message from mallory and one (not neccesarily
+    the same message) with Subject containing the word "crypto".
+    ::
+       % notmuch search 'thread:"{from:mallory}" and thread:"{subject:crypto}"'
+    The performance of such queries can vary wildly. To understand
+    this, the user should think of the query **thread:{<something>}**
+    as expanding to all of the thread IDs which match **<something>**;
+    notmuch then performs a second search using the expanded query.
 path:<directory-path> or path:<directory-path>/** or path:/<regex>/
     The **path:** prefix searches for email messages that are in
     particular directories within the mail store. The directory must
@@ -277,8 +293,8 @@ Quoting
 Double quotes are also used by the notmuch query parser to protect
-boolean terms or regular expressions containing spaces or other
-special characters, e.g.
+boolean terms, regular expressions, or subqueries containing spaces or
+other special characters, e.g.
@@ -288,12 +304,17 @@ special characters, e.g.
+   thread:"{from:mallory and date:2009}"
 As with phrases, you need to protect the double quotes from the shell
    % notmuch search 'folder:"/^.*/(Junk|Spam)$/"'
+   % notmuch search 'thread:"{from:mallory and date:2009}" and thread:{to:mallory}'
@@ -435,6 +456,7 @@ 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\\]/"
+- thread subqueries, e.g. "thread:{from:bob}"

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