lib: add thread subqueries.

This change allows queries of the form

 thread:{from:me} and thread:{from:jian} and not thread:{from:dave}

This is still somewhat brute-force, but it's a big improvement over
both the shell script solution and the previous proposal [1], because it
does not build the whole thread structure just generate a
query. A further potential optimization is to replace the calls to
notmuch with more specialized Xapian code; in particular it's not
likely that reading all of the message metadata is a win here.

[1]: id:20170820213240.20526-1-david@tethera.net

lib/Makefile.local

@@ -58,7 +58,8 @@ libnotmuch_cxx_srcs =		\
 	$(dir)/query-fp.cc      \
 	$(dir)/config.cc	\
 	$(dir)/regexp-fields.cc	\
-	$(dir)/thread.cc
+	$(dir)/thread.cc \
+	$(dir)/thread-fp.cc
 
 libnotmuch_modules := $(libnotmuch_c_srcs:.c=.o) $(libnotmuch_cxx_srcs:.cc=.o)
 

lib/database.cc

@@ -21,6 +21,7 @@
 #include "database-private.h"
 #include "parse-time-vrp.h"
 #include "query-fp.h"
+#include "thread-fp.h"
 #include "regexp-fields.h"
 #include "string-util.h"
 
@@ -258,7 +259,8 @@ prefix_t prefix_table[] = {
     { "directory",		"XDIRECTORY",	NOTMUCH_FIELD_NO_FLAGS },
     { "file-direntry",		"XFDIRENTRY",	NOTMUCH_FIELD_NO_FLAGS },
     { "directory-direntry",	"XDDIRENTRY",	NOTMUCH_FIELD_NO_FLAGS },
-    { "thread",			"G",		NOTMUCH_FIELD_EXTERNAL },
+    { "thread",			"G",		NOTMUCH_FIELD_EXTERNAL |
+						NOTMUCH_FIELD_PROCESSOR },
     { "tag",			"K",		NOTMUCH_FIELD_EXTERNAL |
 						NOTMUCH_FIELD_PROCESSOR },
     { "is",			"K",		NOTMUCH_FIELD_EXTERNAL |
@@ -317,6 +319,8 @@ _setup_query_field (const prefix_t *prefix, notmuch_database_t *notmuch)
 	    fp = (new DateFieldProcessor())->release ();
 	else if (STRNCMP_LITERAL(prefix->name, "query") == 0)
 	    fp = (new QueryFieldProcessor (*notmuch->query_parser, notmuch))->release ();
+	else if (STRNCMP_LITERAL(prefix->name, "thread") == 0)
+	    fp = (new ThreadFieldProcessor (*notmuch->query_parser, notmuch))->release ();
 	else
 	    fp = (new RegexpFieldProcessor (prefix->name, prefix->flags,
 					    *notmuch->query_parser, notmuch))->release ();

lib/thread-fp.cc

@@ -0,0 +1,67 @@
+/* thread-fp.cc - "thread:" field processor glue
+ *
+ * This file is part of notmuch.
+ *
+ * Copyright © 2018 David Bremner
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see https://www.gnu.org/licenses/ .
+ *
+ * Author: David Bremner <david@tethera.net>
+ */
+
+#include "database-private.h"
+#include "thread-fp.h"
+#include <iostream>
+
+#if HAVE_XAPIAN_FIELD_PROCESSOR
+
+Xapian::Query
+ThreadFieldProcessor::operator() (const std::string & str)
+{
+    notmuch_status_t status;
+    const char *thread_prefix = _find_prefix ("thread");
+
+    if (str.at (0) == '{') {
+	if (str.size () <= 1 || str.at (str.size () - 1) != '}') {
+	    throw Xapian::QueryParserError ("missing } in '" + str + "'");
+	} else {
+	    std::string subquery_str = str.substr (1, str.size () - 2);
+	    notmuch_query_t *subquery = notmuch_query_create (notmuch, subquery_str.c_str ());
+	    notmuch_messages_t *messages;
+	    std::set<std::string> terms;
+
+	    if (! subquery)
+		throw Xapian::QueryParserError ("failed to create subquery for '" + subquery_str + "'");
+
+	    status = notmuch_query_search_messages (subquery, &messages);
+	    if (status)
+		throw Xapian::QueryParserError ("failed to search messages for '" + subquery_str + "'");
+
+	    for (; notmuch_messages_valid (messages); notmuch_messages_move_to_next (messages)) {
+		std::string term = thread_prefix;
+		notmuch_message_t *message;
+		message = notmuch_messages_get (messages);
+		term += notmuch_message_get_thread_id (message);
+		terms.insert (term);
+	    }
+	    return Xapian::Query (Xapian::Query::OP_OR, terms.begin (), terms.end ());
+	}
+    } else {
+	/* literal thread id */
+	std::string term = thread_prefix + str;
+	return Xapian::Query (term);
+    }
+
+}
+#endif

lib/thread-fp.h

@@ -0,0 +1,42 @@
+/* thread-fp.h - thread field processor glue
+ *
+ * This file is part of notmuch.
+ *
+ * Copyright © 2018 David Bremner
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see https://www.gnu.org/licenses/ .
+ *
+ * Author: David Bremner <david@tethera.net>
+ */
+
+#ifndef NOTMUCH_THREAD_FP_H
+#define NOTMUCH_THREAD_FP_H
+
+#include <xapian.h>
+#include "notmuch.h"
+
+#if HAVE_XAPIAN_FIELD_PROCESSOR
+class ThreadFieldProcessor : public Xapian::FieldProcessor {
+ protected:
+    Xapian::QueryParser &parser;
+    notmuch_database_t *notmuch;
+
+ public:
+    ThreadFieldProcessor (Xapian::QueryParser &parser_, notmuch_database_t *notmuch_)
+	: parser(parser_), notmuch(notmuch_) { };
+
+    Xapian::Query operator()(const std::string & str);
+};
+#endif
+#endif /* NOTMUCH_THREAD_FP_H */

test/T585-thread-subquery.sh

@@ -0,0 +1,46 @@
+#!/usr/bin/env bash
+#
+# Copyright (c) 2018 David Bremner
+#
+
+test_description='test of searching by using thread subqueries'
+
+. $(dirname "$0")/test-lib.sh || exit 1
+
+add_email_corpus
+
+test_begin_subtest "Basic query that matches no messages"
+count=$(notmuch count from:keithp and to:keithp)
+test_expect_equal 0 "$count"
+
+test_begin_subtest "Same query against threads"
+notmuch search thread:{from:keithp} and thread:{to:keithp} | notmuch_search_sanitize > OUTPUT
+cat<<EOF > EXPECTED
+thread:XXX   2009-11-18 [7/7] Lars Kellogg-Stedman, Mikhail Gusarov, Keith Packard, Carl Worth; [notmuch] Working with Maildir storage? (inbox signed unread)
+EOF
+test_expect_equal_file EXPECTED OUTPUT
+
+test_begin_subtest "Mix thread and non-threads query"
+notmuch search thread:{from:keithp} and to:keithp | notmuch_search_sanitize > OUTPUT
+cat<<EOF > EXPECTED
+thread:XXX   2009-11-18 [1/7] Lars Kellogg-Stedman| Mikhail Gusarov, Keith Packard, Carl Worth; [notmuch] Working with Maildir storage? (inbox signed unread)
+EOF
+test_expect_equal_file EXPECTED OUTPUT
+
+test_begin_subtest "Compound subquery"
+notmuch search 'thread:"{from:keithp and date:2009}" and thread:{to:keithp}' | notmuch_search_sanitize > OUTPUT
+cat<<EOF > EXPECTED
+thread:XXX   2009-11-18 [7/7] Lars Kellogg-Stedman, Mikhail Gusarov, Keith Packard, Carl Worth; [notmuch] Working with Maildir storage? (inbox signed unread)
+EOF
+test_expect_equal_file EXPECTED OUTPUT
+
+test_begin_subtest "Syntax/quoting error in subquery"
+notmuch search 'thread:{from:keithp and date:2009} and thread:{to:keithp}' 1>OUTPUT 2>&1
+cat<<EOF > EXPECTED
+notmuch search: A Xapian exception occurred
+A Xapian exception occurred parsing query: missing } in '{from:keithp'
+Query string was: thread:{from:keithp and date:2009} and thread:{to:keithp}
+EOF
+test_expect_equal_file EXPECTED OUTPUT
+
+test_done