Made pronunciation::rhymes join dynamic

This involved adding a new type of filter; one that compares (currently
only equality and inequality) a field with another field located in an
enclosing join context.

In the process, it was discovered that simplifying the lemma::forms join
field earlier actually made some queries return inaccurate results
because the inflection of the form was being ignored and anything in the
lemma would be used because of the inner join. Because the existing
condition join did not allow for the condition field to be on the from
side of the join, two things were done: a condition version of
joinThrough was made, and lemma was finally eliminated as a top-level
object, replaced instead with a condition join between word and form
through lemmas_forms.

Queries are also now grouped by the first select field (assumed to be
the primary ID) of the top table, in order to eliminate duplicates
created by inner joins, so that there is a uniform distribution between
results for random queries.

Created a database index on pronunciations(rhyme) which decreases query
time for rhyming filters. The new database version is
backwards-compatible because no data or structure changed.

1 files changed, 17 insertions, 6 deletions

@@ -12,7 +12,6 @@ struct sqlite3_stmt;
 namespace verbly {
   
   class form;
-  class lemma;
   class word;
   class database;
   
@@ -131,14 +130,26 @@ namespace verbly {
       return (id == id_);
     }
     
-    static filter rhymesWith(const pronunciation& arg);
-    static filter rhymesWith(const class form& arg);
-    static filter rhymesWith(const lemma& arg);
-    static filter rhymesWith(const word& arg);
-    
     // Relationships to other objects
     
     static const field forms;
+
+    // Rhyming relationship
+
+    class rhymes_field {
+    public:
+
+      filter operator%=(filter joinCondition) const;
+
+      operator filter() const;
+
+    private:
+
+      static const field rhymeJoin;
+
+    };
+
+    static const rhymes_field rhymes;
     
   private:
     bool valid_ = false;