If query substituting placeholder is empty, pass true expression instead

This allows uniform usage of views both with and without any extra
conditions. Also optimize some common cases so that we don't have
useless WHERE TRUE clauses or (...) AND (TRUE) expressions.

1 files changed, 31 insertions, 30 deletions

diff --git a/odb/sqlite/query.hxx b/odb/sqlite/query.hxx
index c712b58..a3c63ba 100644
--- a/odb/sqlite/query.hxx
+++ b/odb/sqlite/query.hxx
@@ -121,14 +121,17 @@ namespace odb
         {
           column,
           param,
-          native
+          native,
+          boolean
         };
 
         clause_part (kind_type k): kind (k) {}
         clause_part (kind_type k, const std::string& p): kind (k), part (p) {}
+        clause_part (bool p): kind (boolean), bool_part (p) {}
 
         kind_type kind;
         std::string part;
+        bool bool_part;
       };
 
       query ()
@@ -142,7 +145,7 @@ namespace odb
       query (bool v)
         : parameters_ (new (details::shared) query_params)
       {
-        clause_.push_back (clause_part (clause_part::native, v ? "1" : "0"));
+        clause_.push_back (clause_part (v));
       }
 
       explicit
@@ -203,6 +206,26 @@ namespace odb
       parameters () const;
 
     public:
+      bool
+      empty () const
+      {
+        return clause_.empty ();
+      }
+
+      static const query true_expr;
+
+      bool
+      const_true () const
+      {
+        return clause_.size () == 1 &&
+          clause_.front ().kind == clause_part::boolean &&
+          clause_.front ().bool_part;
+      }
+
+      void
+      optimize ();
+
+    public:
       template <typename T>
       static val_bind<T>
       _val (const T& x)
@@ -370,36 +393,14 @@ namespace odb
       return r;
     }
 
-    inline query
-    operator&& (const query& x, const query& y)
-    {
-      query r ("(");
-      r += x;
-      r += ") AND (";
-      r += y;
-      r += ")";
-      return r;
-    }
+    query
+    operator&& (const query&, const query&);
 
-    inline query
-    operator|| (const query& x, const query& y)
-    {
-      query r ("(");
-      r += x;
-      r += ") OR (";
-      r += y;
-      r += ")";
-      return r;
-    }
+    query
+    operator|| (const query&, const query&);
 
-    inline query
-    operator! (const query& x)
-    {
-      query r ("NOT (");
-      r += x;
-      r += ")";
-      return r;
-    }
+    query
+    operator! (const query&);
 
     // query_column
     //