Changed postgresql and postgresql_psycopg2 backends NOT to do a SELECT version() for every connection, which was ludicrous. Now the version is only retrieved if it needs to be, via a lazy loader.

git-svn-id: http://code.djangoproject.com/svn/django/trunk@6012 bcc190cf-cafb-0310-a4f2-bffc1f526a37

django/db/backends/postgresql/base.py

@@ -102,9 +102,6 @@ class DatabaseWrapper(BaseDatabaseWrapper):
             cursor.execute("SET TIME ZONE %s", [settings.TIME_ZONE])
         cursor.execute("SET client_encoding to 'UNICODE'")
         cursor = UnicodeCursorWrapper(cursor, 'utf-8')
-        if self.ops.postgres_version is None:
-            cursor.execute("SELECT version()")
-            self.ops.postgres_version = [int(val) for val in cursor.fetchone()[0].split()[1].split('.')]
         return cursor
 
 def typecast_string(s):

django/db/backends/postgresql/operations.py

@@ -4,8 +4,17 @@ from django.db.backends import BaseDatabaseOperations
 # used by both the 'postgresql' and 'postgresql_psycopg2' backends.
 
 class DatabaseOperations(BaseDatabaseOperations):
-    def __init__(self, postgres_version=None):
+    def __init__(self):
-        self.postgres_version = postgres_version
+        self._postgres_version = None
+
+    def _get_postgres_version(self):
+        if self._postgres_version is None:
+            from django.db import connection
+            cursor = connection.cursor()
+            cursor.execute("SELECT version()")
+            self._postgres_version = [int(val) for val in cursor.fetchone()[0].split()[1].split('.')]
+        return self._postgres_version
+    postgres_version = property(_get_postgres_version)
 
     def date_extract_sql(self, lookup_type, field_name):
         # http://www.postgresql.org/docs/8.0/static/functions-datetime.html#FUNCTIONS-DATETIME-EXTRACT
@@ -92,4 +101,4 @@ class DatabaseOperations(BaseDatabaseOperations):
                     style.SQL_KEYWORD('IS NOT'),
                     style.SQL_KEYWORD('FROM'),
                     style.SQL_TABLE(f.m2m_db_table())))
-        return output
+        return output

django/db/backends/postgresql_psycopg2/base.py

@@ -64,7 +64,4 @@ class DatabaseWrapper(BaseDatabaseWrapper):
         cursor.tzinfo_factory = None
         if set_tz:
             cursor.execute("SET TIME ZONE %s", [settings.TIME_ZONE])
-        if self.ops.postgres_version is None:
-            cursor.execute("SELECT version()")
-            self.ops.postgres_version = [int(val) for val in cursor.fetchone()[0].split()[1].split('.')]
         return cursor