- clarified LoaderStrategy implementations, centralized deferred column loading

into DeferredColumnLoader (i.e. deferred polymorphic loader)
- added generic deferred_load(instance, props) method, will set up "deferred" or "lazy"
loads across a set of properties.
- mapper post-fetch now uses all deferreds, no more post-selects inside a flush() [ticket:652]

2 files changed, 25 insertions, 9 deletions

diff --git a/lib/sqlalchemy/engine/base.py b/lib/sqlalchemy/engine/base.py
index fc4433a47..ca602b58c 100644
--- a/lib/sqlalchemy/engine/base.py
+++ b/lib/sqlalchemy/engine/base.py
@@ -300,6 +300,11 @@ class ExecutionContext(object):
             (i.e. dict or list of dicts for non positional,
             list or list of lists/tuples for positional).
             
+        isinsert
+          True if the statement is an INSERT
+            
+        isupdate
+          True if the statement is an UPDATE
     
     The Dialect should provide an ExecutionContext via the
     create_execution_context() method.  The `pre_exec` and `post_exec`
@@ -388,6 +393,12 @@ class ExecutionContext(object):
 
         raise NotImplementedError()
 
+    def postfetch_cols(self):
+        """return a list of Column objects for which a 'passive' server-side default
+        value was fired off"""
+
+        raise NotImplementedError()
+
 class Compiled(object):
     """Represent a compiled SQL expression.
 
@@ -1215,6 +1226,7 @@ class ResultProxy(object):
 
         return self.context.lastrow_has_defaults()
 
+        
     def supports_sane_rowcount(self):
         """Return ``supports_sane_rowcount()`` from the underlying ExecutionContext.
 
diff --git a/lib/sqlalchemy/engine/default.py b/lib/sqlalchemy/engine/default.py
index 962e2ab60..a2e159639 100644
--- a/lib/sqlalchemy/engine/default.py
+++ b/lib/sqlalchemy/engine/default.py
@@ -6,7 +6,7 @@
 
 """Provide default implementations of per-dialect sqlalchemy.engine classes"""
 
-from sqlalchemy import schema, exceptions, sql, types
+from sqlalchemy import schema, exceptions, sql, types, util
 import sys, re
 from sqlalchemy.engine import base
 
@@ -147,6 +147,7 @@ class DefaultExecutionContext(base.ExecutionContext):
         self.dialect = dialect
         self.connection = connection
         self.compiled = compiled
+        self._postfetch_cols = util.Set()
         
         if compiled is not None:
             self.typemap = compiled.typemap
@@ -173,6 +174,8 @@ class DefaultExecutionContext(base.ExecutionContext):
         self.cursor = self.create_cursor()
         
     engine = property(lambda s:s.connection.engine)
+    isinsert = property(lambda s:s.compiled and s.compiled.isinsert)
+    isupdate = property(lambda s:s.compiled and s.compiled.isupdate)
     
     def __encode_param_keys(self, params):
         """apply string encoding to the keys of dictionary-based bind parameters"""
@@ -255,8 +258,11 @@ class DefaultExecutionContext(base.ExecutionContext):
         return self._last_updated_params
 
     def lastrow_has_defaults(self):
-        return self._lastrow_has_defaults
+        return len(self._postfetch_cols)
 
+    def postfetch_cols(self):
+        return self._postfetch_cols
+        
     def set_input_sizes(self):
         """Given a cursor and ClauseParameters, call the appropriate
         style of ``setinputsizes()`` on the cursor, using DBAPI types
@@ -291,13 +297,12 @@ class DefaultExecutionContext(base.ExecutionContext):
         and generate last_inserted_ids() collection."""
 
         # TODO: cleanup
-        if self.compiled.isinsert:
+        if self.isinsert:
             if isinstance(self.compiled_parameters, list):
                 plist = self.compiled_parameters
             else:
                 plist = [self.compiled_parameters]
             drunner = self.dialect.defaultrunner(self)
-            self._lastrow_has_defaults = False
             for param in plist:
                 last_inserted_ids = []
                 # check the "default" status of each column in the table
@@ -305,7 +310,7 @@ class DefaultExecutionContext(base.ExecutionContext):
                     # check if it will be populated by a SQL clause - we'll need that
                     # after execution.
                     if c in self.compiled.inline_params:
-                        self._lastrow_has_defaults = True
+                        self._postfetch_cols.add(c)
                         if c.primary_key:
                             last_inserted_ids.append(None)
                     # check if its not present at all.  see if theres a default
@@ -315,7 +320,7 @@ class DefaultExecutionContext(base.ExecutionContext):
                     # the SQL-generated value after execution.
                     elif not c.key in param or param.get_original(c.key) is None:
                         if isinstance(c.default, schema.PassiveDefault):
-                            self._lastrow_has_defaults = True
+                            self._postfetch_cols.add(c)
                         newid = drunner.get_column_default(c)
                         if newid is not None:
                             param.set_value(c.key, newid)
@@ -331,20 +336,19 @@ class DefaultExecutionContext(base.ExecutionContext):
                 # here (hard to do since lastrowid doesnt support it either)
                 self._last_inserted_ids = last_inserted_ids
                 self._last_inserted_params = param
-        elif self.compiled.isupdate:
+        elif self.isupdate:
             if isinstance(self.compiled_parameters, list):
                 plist = self.compiled_parameters
             else:
                 plist = [self.compiled_parameters]
             drunner = self.dialect.defaultrunner(self)
-            self._lastrow_has_defaults = False
             for param in plist:
                 # check the "onupdate" status of each column in the table
                 for c in self.compiled.statement.table.c:
                     # it will be populated by a SQL clause - we'll need that
                     # after execution.
                     if c in self.compiled.inline_params:
-                        pass
+                        self._postfetch_cols.add(c)
                     # its not in the bind parameters, and theres an "onupdate" defined for the column;
                     # execute it and add to bind params
                     elif c.onupdate is not None and (not c.key in param or param.get_original(c.key) is None):