Reverted isolation level values to backward compatible values

This basically removes the READ UNCOMMITED level (that internally
PostgreSQL maps to READ COMMITED anyway) to keep the numeric values
compattible with old psycopg versions. For full details and discussion
see this thread:
http://archives.postgresql.org/psycopg/2011-12/msg00008.php

4 files changed, 21 insertions, 23 deletions

diff --git a/lib/extensions.py b/lib/extensions.py
index de022dd..bedb246 100644
--- a/lib/extensions.py
+++ b/lib/extensions.py
@@ -69,10 +69,12 @@ except ImportError:
 
 """Isolation level values."""
 ISOLATION_LEVEL_AUTOCOMMIT          = 0
-ISOLATION_LEVEL_READ_UNCOMMITTED    = 1
-ISOLATION_LEVEL_READ_COMMITTED      = 2
-ISOLATION_LEVEL_REPEATABLE_READ     = 3
-ISOLATION_LEVEL_SERIALIZABLE        = 4
+ISOLATION_LEVEL_READ_COMMITTED      = 1
+ISOLATION_LEVEL_REPEATABLE_READ     = 2
+ISOLATION_LEVEL_SERIALIZABLE        = 3
+
+# PostgreSQL internally converts uncommited to commited
+ISOLATION_LEVEL_READ_UNCOMMITTED = ISOLATION_LEVEL_READ_COMMITTED
 
 """psycopg connection status values."""
 STATUS_SETUP    = 0
diff --git a/psycopg/connection_int.c b/psycopg/connection_int.c
index 441d362..41b73f1 100644
--- a/psycopg/connection_int.c
+++ b/psycopg/connection_int.c
@@ -39,10 +39,10 @@
 
 const IsolationLevel conn_isolevels[] = {
     {"",                    0}, /* autocommit */
-    {"read uncommitted",    1},
-    {"read committed",      2},
-    {"repeatable read",     3},
-    {"serializable",        4},
+    {"read committed",      1},
+    {"read uncommitted",    1}, /* comes after to report real level */
+    {"repeatable read",     2},
+    {"serializable",        3},
     {"default",            -1},
     { NULL }
 };
@@ -1041,9 +1041,8 @@ conn_switch_isolation_level(connectionObject *self, int level)
 
     /* use only supported levels on older PG versions */
     if (self->server_version < 80000) {
-        if (level == 1 || level == 3) {
-            ++level;
-        }
+        if (level == 2)
+            level = 3;
     }
 
     if (-1 == (curr_level = conn_get_isolation_level(self))) {
diff --git a/psycopg/connection_type.c b/psycopg/connection_type.c
index 2bb0e70..02bc4da 100644
--- a/psycopg/connection_type.c
+++ b/psycopg/connection_type.c
@@ -405,13 +405,15 @@ _psyco_conn_parse_isolevel(connectionObject *self, PyObject *pyval)
     if (PyInt_Check(pyval)) {
         long level = PyInt_AsLong(pyval);
         if (level == -1 && PyErr_Occurred()) { goto exit; }
-        if (level < 1 || level > 4) {
+        if (level < 1 || level > 3) {
             PyErr_SetString(PyExc_ValueError,
-                "isolation_level must be between 1 and 4");
+                "isolation_level must be between 1 and 3");
             goto exit;
         }
 
-        isolevel = conn_isolevels + level;
+        isolevel = conn_isolevels;
+        while ((++isolevel)->value != level)
+            ; /* continue */
     }
 
     /* parse from the string -- this includes "default" */
diff --git a/tests/test_connection.py b/tests/test_connection.py
index a887313..0a79144 100755
--- a/tests/test_connection.py
+++ b/tests/test_connection.py
@@ -206,7 +206,6 @@ class IsolationLevelsTestCase(unittest.TestCase):
 
         levels = [
             (None, psycopg2.extensions.ISOLATION_LEVEL_AUTOCOMMIT),
-            ('read uncommitted', psycopg2.extensions.ISOLATION_LEVEL_READ_UNCOMMITTED),
             ('read committed', psycopg2.extensions.ISOLATION_LEVEL_READ_COMMITTED),
             ('repeatable read', psycopg2.extensions.ISOLATION_LEVEL_REPEATABLE_READ),
             ('serializable', psycopg2.extensions.ISOLATION_LEVEL_SERIALIZABLE),
@@ -216,10 +215,8 @@ class IsolationLevelsTestCase(unittest.TestCase):
 
             # the only values available on prehistoric PG versions
             if conn.server_version < 80000:
-                if level in (
-                        psycopg2.extensions.ISOLATION_LEVEL_READ_UNCOMMITTED,
-                        psycopg2.extensions.ISOLATION_LEVEL_REPEATABLE_READ):
-                    name, level = levels[levels.index((name, level)) + 1]
+                if level == psycopg2.extensions.ISOLATION_LEVEL_REPEATABLE_READ:
+                    name, level = ('serializable', psycopg2.extensions.ISOLATION_LEVEL_SERIALIZABLE)
 
             self.assertEqual(conn.isolation_level, level)
 
@@ -771,13 +768,11 @@ class TransactionControlTests(unittest.TestCase):
         self.assertEqual(cur.fetchone()[0], 'read committed')
         self.conn.rollback()
 
+        # 'read uncommitted' is internally translated to 'read committed'
         self.conn.set_session(
             isolation_level=psycopg2.extensions.ISOLATION_LEVEL_READ_UNCOMMITTED)
         cur.execute("SHOW default_transaction_isolation;")
-        if self.conn.server_version > 80000:
-            self.assertEqual(cur.fetchone()[0], 'read uncommitted')
-        else:
-            self.assertEqual(cur.fetchone()[0], 'read committed')
+        self.assertEqual(cur.fetchone()[0], 'read committed')
         self.conn.rollback()
 
     def test_set_isolation_level_str(self):