Database: add tags method for getting set of tag names

The database class now separatly tracks tag information. So for the one
place where all the inclusions were iterated over in order to build up a
tag set, we now instead ask the database for this set directly.

Related to issue #245

src/Database.cpp

@@ -260,6 +260,12 @@ std::vector <std::string> Database::files () const
   return all;
 }
 
+////////////////////////////////////////////////////////////////////////////////
+std::set <std::string> Database::tags () const
+{
+  return _tagInfoDatabase.tags ();
+}
+
 ////////////////////////////////////////////////////////////////////////////////
 // Return most recent line from database 
 std::string Database::firstLine ()

src/Database.h

@@ -97,6 +97,7 @@ public:
   void initialize (const std::string&, Journal& journal);
   void commit ();
   std::vector <std::string> files () const;
+  std::set <std::string> tags () const;
 
   std::string firstLine ();
 

src/TagInfoDatabase.cpp

@@ -74,6 +74,21 @@ void TagInfoDatabase::add (const std::string& tag, const TagInfo& tagInfo)
   _tagInformation.emplace (tag, tagInfo);
 }
 
+///////////////////////////////////////////////////////////////////////////////
+// Return the current set of tag names
+//
+std::set <std::string> TagInfoDatabase::tags () const
+{
+  std::set <std::string> tags; 
+
+  for (auto& item : _tagInformation)
+  {
+    tags.insert (item.first);
+  }
+
+  return tags;
+}
+
 ///////////////////////////////////////////////////////////////////////////////
 std::string TagInfoDatabase::toJson ()
 {

src/TagInfoDatabase.h

@@ -27,6 +27,7 @@
 #ifndef INCLUDED_TAGINFODATABASE
 #define INCLUDED_TAGINFODATABASE
 
+#include <set>
 #include <string>
 #include <map>
 #include <TagInfo.h>
@@ -39,6 +40,8 @@ public:
 
   void add (const std::string&, const TagInfo&);
 
+  std::set <std::string> tags () const;
+
   std::string toJson ();
 
 private:

src/dom.cpp

@@ -177,11 +177,8 @@ bool domGet (
 
     else if (pig.skipLiteral ("tag."))
     {
-      // Generate a unique, ordered list of tags.
+      // get unique, ordered list of tags.
-      std::set <std::string> tags;
+      std::set <std::string> tags = database.tags ();
-      for (auto& interval : getAllInclusions (database))
-        for (auto& tag : interval.tags ())
-          tags.insert (tag);
 
       // dom.tag.count
       if (pig.skipLiteral ("count"))