From: Mike Bayer <mike_mp@zzzcomputing.com>
Date: Sun, 25 Oct 2009 01:40:23 +0000 (+0000)
Subject: - Fixed a slight inaccuracy in the sharding example.
X-Git-Tag: rel_0_6beta1~225
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=ed83a844bb143c5b04514800907726e875bf1e82;p=thirdparty%2Fsqlalchemy%2Fsqlalchemy.git

- Fixed a slight inaccuracy in the sharding example.
Comparing equivalence of columns in the ORM is best
accomplished using col1.shares_lineage(col2).
[ticket:1491]
---

diff --git a/CHANGES b/CHANGES
index 5697efc993..5a3ba9c45c 100644
--- a/CHANGES
+++ b/CHANGES
@@ -658,6 +658,11 @@ CHANGES
       the column will be propagated down to 
       subclasses. [ticket:1570]  This is the reverse
       situation as that of [ticket:1523], fixed in 0.5.6.
+
+    - Fixed a slight inaccuracy in the sharding example.
+      Comparing equivalence of columns in the ORM is best 
+      accomplished using col1.shares_lineage(col2).
+      [ticket:1491]
       
 0.5.6
 =====
diff --git a/examples/sharding/attribute_shard.py b/examples/sharding/attribute_shard.py
index 2f03a5a344..2ac0c88ff8 100644
--- a/examples/sharding/attribute_shard.py
+++ b/examples/sharding/attribute_shard.py
@@ -134,7 +134,13 @@ def query_chooser(query):
     # and convert to shard ids
     class FindContinent(sql.ClauseVisitor):
         def visit_binary(self, binary):
-            if binary.left is weather_locations.c.continent:
+            # "shares_lineage()" returns True if both columns refer to the same
+            # statement column, adjusting for any annotations present.
+            # (an annotation is an internal clone of a Column object
+            # and occur when using ORM-mapped attributes like 
+            # "WeatherLocation.continent"). A simpler comparison, though less accurate, 
+            # would be "binary.left.key == 'continent'".
+            if binary.left.shares_lineage(weather_locations.c.continent):
                 if binary.operator == operators.eq:
                     ids.append(shard_lookup[binary.right.value])
                 elif binary.operator == operators.in_op:
diff --git a/test/orm/sharding/test_shard.py b/test/orm/sharding/test_shard.py
index e8ffaa7cad..06a38848bd 100644
--- a/test/orm/sharding/test_shard.py
+++ b/test/orm/sharding/test_shard.py
@@ -87,7 +87,7 @@ class ShardTest(TestBase):
 
             class FindContinent(sql.ClauseVisitor):
                 def visit_binary(self, binary):
-                    if binary.left is weather_locations.c.continent:
+                    if binary.left.shares_lineage(weather_locations.c.continent):
                         if binary.operator == operators.eq:
                             ids.append(shard_lookup[binary.right.value])
                         elif binary.operator == operators.in_op: