PRB: Distributed Queries Return Error 7356 with MSDAORA (251238)

SYMPTOMS

If metadata information changes at execution time, the following error occurs:

Server: Msg 7356, Level 16, State 1, Line 1
OLE DB provider 'MSDAORA' supplied inconsistent metadata for a column.

This error may occur when you use distributed queries in SQL Server that reference a view if you create the underlying table in Oracle under the following conditions:

You do not specify Nullability in the CREATE TABLE statement. -and-
You create a Primary Key using the ALTER TABLE statement -and-
You create a view that includes the PRIMARY KEY.

CAUSE

IDBSchemaRowset::GetRowset for DBSCHEMA_COLUMNS returns IS_NULLABLE as TRUE.

IColumnsInfo::GetColumnInfo on the rowset returns DBCOLUMNFLAGS_ISNULL as FALSE.

Because of the these discrepancies, distributed queries fail with the 7356 error.

The OLE DB provider, Msdaora.dll, returns the wrong information because the metadata that Oracle returns is incorrect.

MORE INFORMATION

Steps to Reproduce Behavior

Use these steps to reproduce the behavior:

Create the test table using this code:

CREATE TABLE MYDIST
      (GMI_ID  VARCHAR2(8)
      ,LAST_NAME VARCHAR2(20)
      ,FIRST_NAME VARCHAR2(20) )

Alter the table using this code:

   ALTER TABLE MYDIST
      ADD (CONSTRAINT MYDIST_PK PRIMARY KEY (GMI_ID))

Insert data into the table using this code:

   INSERT INTO MYDIST VALUES ('test1','row','one')
   INSERT INTO MYDIST VALUES ('test2','row','two')

Create a view using this:

   CREATE VIEW V_MYDIST1 AS
      SELECT GMI_ID FROM MYDIST

Create a linked server entry using the msdaora.dll file and execute the following query:
```
select * from <OracleLinkedServer>..<SchemaName>.V_MYDIST1
					
```
The query returns this error:
Server: Msg 7356, Level 16, State 1, Line 1
OLE DB provider 'MSDAORA' supplied inconsistent metadata for a column. Metadata information was changed at execution time.