Ticket #1601: simulate_offset_auto.diff

paginate.py

@@ -31 +31 @@
 
 log = logging.getLogger("turbogears.paginate")
 
+# lists of databases that lack support for OFFSET
+# this will need to be updated periodically as modules change
+_so_no_offset = 'mssql maxdb sybase'.split()
+_sa_no_offset = 'mssql maxdb access'.split()
+
+# this is a global that is set the first time paginate() is called
+_simulate_offset = None
+
 def paginate(var_name, default_order='', default_reversed=False, limit=10,
             allow_limit_override=False, max_pages=5, dynamic_limit=None):
     '''
@@ -200 +208 @@
             # we replace the var with the sliced one
             endpoint = offset + limit_
             log.debug("slicing data between %d and %d", offset, endpoint)
-            output[var_name] = var_data[offset:endpoint]
 
+            global _simulate_offset
+            get = turbogears.config.get
+            if _simulate_offset is None:
+                _simulate_offset = get('paginate.simulate_offset', None)
+                if _simulate_offset is None:
+                    _simulate_offset = False
+                    so_db = get('sqlobject.dburi', 'NOMATCH:').split(':', 1)[0]
+                    sa_db = get('sqlalchemy.dburi', 'NOMATCH:').split(':', 1)[0]
+                    if so_db in _so_no_offset or sa_db in _sa_no_offset:
+                        _simulate_offset = True
+                        log.warning("simulating OFFSET, paginate may be slow")
+                        log.warning("to turn off, set "
+                                     "paginate.simulate_offset=False")
+
+            if _simulate_offset:
+                var_data_iter = iter(var_data[:endpoint])
+                # skip over the number of records specified by offset
+                for i in range(offset):   
+                    var_data_iter.next()
+                # return the records that remain
+                output[var_name] = list(var_data_iter)
+            else:
+                output[var_name] = var_data[offset:endpoint]
+
             return output
         return decorated
     return weak_signature_decorator(entangle)