visit_select needs more testing with limit clause #20

sqlalchemy_teradata/compiler.py

@@ -9,52 +9,12 @@
 from sqlalchemy import exc
 from sqlalchemy import schema as sa_schema
 from sqlalchemy.types import Unicode
-
-
-
 from sqlalchemy.ext.compiler import compiles
 from sqlalchemy.sql.expression import Select
 from sqlalchemy import exc, sql
 from sqlalchemy import create_engine
 
 
-@compiles(Select, 'teradata')
-def compile_select(element, compiler, **kw):
-    """
-    """
-
-    if not getattr(element, '_window_visit', None):
-      if element._limit is not None or element._offset is not None:
-          limit, offset = element._limit, element._offset
-
-          orderby=compiler.process(element._order_by_clause)
-          if orderby:
-            element = element._generate()
-            element._window_visit=True
-            #element._limit = None
-            #element._offset = None  cant set to none...
-
-            # add a ROW NUMBER() OVER(ORDER BY) column
-            element = element.column(sql.literal_column('ROW NUMBER() OVER (ORDER BY %s)' % orderby).label('rownum')).order_by(None)
-
-            # wrap into a subquery
-            limitselect = sql.select([c for c in element.alias().c if c.key != 'rownum'])
-
-            limitselect._window_visit=True
-            limitselect._is_wrapper=True
-
-            if offset is not None:
-              limitselect.append_whereclause(sql.column('rownum') > offset)
-              if limit is not None:
-                  limitselect.append_whereclause(sql.column('rownum') <= (limit + offset))
-            else:
-              limitselect.append_whereclause(sql.column("rownum") <= limit)
-
-            element = limitselect
-
-    kw['iswrapper'] = getattr(element, '_is_wrapper', False)
-    return compiler.visit_select(element, **kw)
-
 class TeradataCompiler(compiler.SQLCompiler):
 
     def __init__(self, dialect, statement, column_keys=None, inline=False, **kwargs):
@@ -73,9 +33,8 @@ def get_select_precolumns(self, select, **kwargs):
         pre = select._distinct and "DISTINCT " or ""
 
         #TODO: decide whether we can replace this with the recipe...
-        if (select._limit and select._offset is None):
-            pre+= "TOP %d " % (select._limit)
-
+        if (select._limit is not None and select._offset is None):
+            pre += "TOP %d " % (select._limit)
 
         return pre
 
@@ -648,3 +607,42 @@ def visit_BOOLEAN(self, type_, **kw):
 
    def visit_BYTEINT(self, type_, **kw):
        return 'BYTEINT'
+
+
+
+#@compiles(Select, 'teradata')
+#def compile_select(element, compiler, **kw):
+#    """
+#    """
+#
+#    if not getattr(element, '_window_visit', None):
+#      if element._limit is not None or element._offset is not None:
+#          limit, offset = element._limit, element._offset
+#
+#          orderby=compiler.process(element._order_by_clause)
+#          if orderby:
+#            element = element._generate()
+#            element._window_visit=True
+#            #element._limit = None
+#            #element._offset = None  cant set to none...
+#
+#            # add a ROW NUMBER() OVER(ORDER BY) column
+#            element = element.column(sql.literal_column('ROW NUMBER() OVER (ORDER BY %s)' % orderby).label('rownum')).order_by(None)
+#
+#            # wrap into a subquery
+#            limitselect = sql.select([c for c in element.alias().c if c.key != 'rownum'])
+#
+#            limitselect._window_visit=True
+#            limitselect._is_wrapper=True
+#
+#            if offset is not None:
+#              limitselect.append_whereclause(sql.column('rownum') > offset)
+#              if limit is not None:
+#                  limitselect.append_whereclause(sql.column('rownum') <= (limit + offset))
+#            else:
+#              limitselect.append_whereclause(sql.column("rownum") <= limit)
+#
+#            element = limitselect
+#
+#    kw['iswrapper'] = getattr(element, '_is_wrapper', False)
+#    return compiler.visit_select(element, **kw)