From 7d3b47fc855c183a0269ee4fb8c66d5ef9545f4d Mon Sep 17 00:00:00 2001
From: Boris Kolpackov <boris@codesynthesis.com>
Date: Sun, 2 Oct 2011 17:07:20 +0200
Subject: 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.
---
 odb/pgsql/query.hxx | 62 ++++++++++++++++++++++++++---------------------------
 1 file changed, 31 insertions(+), 31 deletions(-)

(limited to 'odb/pgsql/query.hxx')

diff --git a/odb/pgsql/query.hxx b/odb/pgsql/query.hxx
index 438f2f5..0c3f837 100644
--- a/odb/pgsql/query.hxx
+++ b/odb/pgsql/query.hxx
@@ -95,14 +95,17 @@ 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 ()
@@ -116,8 +119,7 @@ namespace odb
       query (bool v)
         : binding_ (0, 0), native_binding_ (0, 0, 0, 0)
       {
-        clause_.push_back (
-          clause_part (clause_part::native, v ? "TRUE" : "FALSE"));
+        clause_.push_back (clause_part (v));
       }
 
       explicit
@@ -187,6 +189,26 @@ namespace odb
       }
 
     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)
@@ -364,36 +386,14 @@ 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
     //
-- 
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