[soc2010/query-refactor] Moved has_results (implementation of exists()) onto the compiler, where it belongs.

git-svn-id: http://code.djangoproject.com/svn/django/branches/soc2010/query-refactor@13334 bcc190cf-cafb-0310-a4f2-bffc1f526a37

1 files changed, 14 insertions, 0 deletions

diff --git a/django/db/models/sql/compiler.py b/django/db/models/sql/compiler.py
index 2877171fd2..e2788019f3 100644
--- a/django/db/models/sql/compiler.py
+++ b/django/db/models/sql/compiler.py
@@ -662,6 +662,20 @@ class SQLCompiler(object):
         columns = {}
         self.query.deferred_to_data(columns, self.query.deferred_to_columns_cb)
         return columns
+    
+    def has_results(self):
+        q = self.query.clone()
+        q.add_extra({'a': 1}, None, None, None, None, None)
+        q.select = []
+        q.select_fields = []
+        q.default_cols = False
+        q.select_related = False
+        q.set_extra_mask(('a',))
+        q.set_aggregate_mask(())
+        q.clear_ordering(True)
+        q.set_limits(high=1)
+        compiler = q.get_compiler(using=self.using)
+        return bool(compiler.execute_sql(SINGLE))
 
     def results_iter(self):
         """