- Oracle's "native decimal" metadata begins to return

    ambiguous typing information about numerics
    when columns are embedded in subqueries as well
    as when ROWNUM is consulted with subqueries, as we
    do for limit/offset.  We've added these ambiguous
    conditions to the cx_oracle "convert to Decimal()"
    handler, so that we receive numerics as Decimal
    in more cases instead of as floats.  These are
    then converted, if requested, into Integer
    or Float, or otherwise kept as the lossless
    Decimal [ticket:1840].

1 files changed, 10 insertions, 3 deletions

diff --git a/lib/sqlalchemy/dialects/oracle/cx_oracle.py b/lib/sqlalchemy/dialects/oracle/cx_oracle.py
index dd32f3201..01ac1a685 100644
--- a/lib/sqlalchemy/dialects/oracle/cx_oracle.py
+++ b/lib/sqlalchemy/dialects/oracle/cx_oracle.py
@@ -86,10 +86,11 @@ class _OracleNumeric(sqltypes.Numeric):
         # we apply a connection output handler that 
         # returns Decimal for positive precision + scale NUMBER 
         # types
+        
         if dialect.supports_native_decimal:
             if self.asdecimal and self.scale is None:
                 processors.to_decimal_processor_factory(Decimal)
-            elif not self.asdecimal and self.scale > 0:
+            elif not self.asdecimal:
                 return processors.to_float
             else:
                 return None
@@ -465,9 +466,15 @@ class OracleDialect_cx_oracle(OracleDialect):
             
         cx_Oracle = self.dbapi
         def output_type_handler(cursor, name, defaultType, size, precision, scale):
-            # convert all NUMBER with precision + positive scale to Decimal.
+            # convert all NUMBER with precision + positive scale to Decimal,
+            # or zero precision and 0 or neg scale, indicates "don't know",
             # this effectively allows "native decimal" mode.
-            if defaultType == cx_Oracle.NUMBER and precision and scale > 0:
+
+            if defaultType == cx_Oracle.NUMBER \
+                and (
+                    (precision and scale > 0) or \
+                    (not precision and scale <= 0)
+                ):
                 return cursor.var(
                             cx_Oracle.STRING, 
                             255,