- merge r6586 from 0.5 branch, for [ticket:1647]

1 files changed, 9 insertions, 1 deletions

diff --git a/lib/sqlalchemy/dialects/postgresql/base.py b/lib/sqlalchemy/dialects/postgresql/base.py
index 7a9e2e710..a71984be4 100644
--- a/lib/sqlalchemy/dialects/postgresql/base.py
+++ b/lib/sqlalchemy/dialects/postgresql/base.py
@@ -322,8 +322,16 @@ class PGCompiler(compiler.SQLCompiler):
 
     def visit_extract(self, extract, **kwargs):
         field = self.extract_map.get(extract.field, extract.field)
+        affinity = sql_util.determine_date_affinity(extract.expr)
+
+        casts = {sqltypes.Date:'date', sqltypes.DateTime:'timestamp', sqltypes.Interval:'interval', sqltypes.Time:'time'}
+        cast = casts.get(affinity, None)
+        if isinstance(extract.expr, sql.ColumnElement) and cast is not None:
+            expr = extract.expr.op('::')(sql.literal_column(cast))
+        else:
+            expr = extract.expr
         return "EXTRACT(%s FROM %s)" % (
-            field, self.process(extract.expr.op('::')(sql.literal_column('timestamp'))))
+            field, self.process(expr))
 
 class PGDDLCompiler(compiler.DDLCompiler):
     def get_column_specification(self, column, **kwargs):