From e7fb949507874f126bd73ed82626ad3b7a731295 Mon Sep 17 00:00:00 2001
From: maneeshpm <manu.pm55@gmail.com>
Date: Thu, 4 Mar 2021 11:52:09 +0530
Subject: [PATCH] Add subquery_phrase in suggestion search, Update unit tests

---
 src/search.cpp      | 25 ++++++++++++++++++++++++-
 test/suggestion.cpp |  8 ++++----
 2 files changed, 28 insertions(+), 5 deletions(-)

diff --git a/src/search.cpp b/src/search.cpp
index ab53505ae..2bcf0721a 100644
--- a/src/search.cpp
+++ b/src/search.cpp
@@ -115,6 +115,29 @@ setup_queryParser(Xapian::QueryParser* queryParser,
     }
 }
 
+/*
+ * subquery_phrase: selects documents that have the terms in the order of the query
+ * within a specified window.
+ * subquery_and: selects documents that have all the terms in the query.
+ * subquery_phrase by itself is quite exclusive. To include more "similar" docs,
+ * we combine it with subquery_and using OP_OR operator. If a perticular document
+ * has a weight of A in subquery_phrase and B in subquery_and, the net weight of
+ * that document becomes A+B. So the documents closer to the query gets a higher.
+ */
+Xapian::Query parse_query(Xapian::QueryParser* query_parser, std::string qs, int flags, std::string prefix, bool suggestion_mode) {
+    Xapian::Query query, subquery_and;
+    query = subquery_and = query_parser->parse_query(qs, flags, prefix);
+
+    if (suggestion_mode) {
+      query_parser->set_default_op(Xapian::Query::op::OP_PHRASE);
+      Xapian::Query subquery_phrase = query_parser->parse_query(qs);
+      subquery_phrase = Xapian::Query(Xapian::Query::OP_PHRASE, subquery_phrase.get_terms_begin(), subquery_phrase.get_terms_end(), subquery_phrase.get_length());
+      query = Xapian::Query(Xapian::Query::OP_OR, subquery_phrase, subquery_and);
+    }
+
+    return query;
+}
+
 }
 
 Search::Search(const std::vector<Archive>& archives) :
@@ -334,7 +357,7 @@ Search::iterator Search::begin() const {
     }
     Xapian::Query query;
     try {
-      query = queryParser->parse_query(this->query, flags, prefix);
+      query = parse_query(queryParser, this->query, flags, prefix, suggestion_mode);
     } catch (Xapian::QueryParserError& e) {
       estimated_matches_number = 0;
       return nullptr;
diff --git a/test/suggestion.cpp b/test/suggestion.cpp
index 5bee5a708..6bc557245 100644
--- a/test/suggestion.cpp
+++ b/test/suggestion.cpp
@@ -205,9 +205,9 @@ namespace {
 
     std::vector<std::string> resultSet = getSuggestions(archive, "winter autumn summer", archive.getEntryCount());
     std::vector<std::string> expectedResult = {
-                                                "autumn summer winter",
-                                                "summer winter autumn",
                                                 "winter autumn summer terma",
+                                                "autumn summer winter",
+                                                "summer winter autumn"
                                               };
 
     ASSERT_EQ(expectedResult, resultSet);
@@ -274,11 +274,11 @@ namespace {
     // "the wolf of"
     resultSet = getSuggestions(archive, "the wolf of", archive.getEntryCount());
     expectedResult = {
-                       "Hour of the wolf",
                        "The wolf of Shingashina",
                        "The wolf of Wall Street",
                        "The wolf of Wall Street Book",
-                       "Terma termb the wolf of wall street termc"
+                       "Terma termb the wolf of wall street termc",
+                       "Hour of the wolf"
                      };
 
     ASSERT_EQ(expectedResult, resultSet);