Call SQL Server function through the gateway

Question

Hello, Does anyone know if it is possible to call a SQL Server system function such as SERVERPROPERTY through the gateway?
I'd like to call a system function in the same way as a user defined function and not using DBMS_HS_PASSTHROUGH.

Answer 1

Maybe I need to be a little bit more precise. It really depends on the data types being returned. When you look at the SERVERPROPERTY function you mentioned earlier and try to select for example the Collation, then SQl Server will return a SQL_VARIANT data type and that will fail - even using passthrough as SQL_VARIANT is not a supported data type.
Let me use the passthrough example as it allows me to demonstrate it easily:
SQL> SQL> declare
  2  val varchar2(100);
  3  c integer;
  4  nr integer;
  5  begin
  6  c:= dbms_hs_passthrough.open_cursor@DG4MSQL_EMGTW_1123_DB;
  7  dbms_hs_passthrough.parse@DG4MSQL_EMGTW_1123_DB (c, 'SELECT  SERVERPROPERTY(''Collation'') as Collation');
  8  LOOP
  9  nr:= DBMS_Hs_Passthrough.fetch_row@DG4MSQL_EMGTW_1123_DB(c);
10  exit when nr=0;
11  dbms_hs_passthrough.get_value@DG4MSQL_EMGTW_1123_DB(c,1,val);
12  dbms_output.put_line(val);
13  end loop;
14  dbms_hs_passthrough.close_cursor@DG4MSQL_EMGTW_1123_DB(c);
15  end;
16  /
declare
ERROR at line 1:
ORA-28511: lost RPC connection to heterogeneous remote agent using
SID=ORA-28511: lost RPC connection to heterogeneous remote agent using
SID=(DESCRIPTION=(ADDRESS=(PROTOCOL=TCP)(HOST=emeagtw.de.oracle.com)(PORT=11231)
)(CONNECT_DATA=(SERVER=DEDICATED)(SERVICE_NAME=dg4msql)))
ORA-02063: preceding line from DG4MSQL_EMGTW_1123_DB
ORA-06512: at line 6
Process ID: 16919
Session ID: 148 Serial number: 16721
When I now make sure the return value is a char data type by slightly modifying the select and including a convert it will work:
SQL> declare
  2  val varchar2(100);
  3  c integer;
  4  nr integer;
  5  begin
  6  c:= dbms_hs_passthrough.open_cursor@DG4MSQL_EMGTW_1123_DB;
  7  dbms_hs_passthrough.parse@DG4MSQL_EMGTW_1123_DB (c, 'SELECT  convert(char,SERVERPROPERTY(''Collation'')) as Collation');
  8  LOOP
  9  nr:= DBMS_Hs_Passthrough.fetch_row@DG4MSQL_EMGTW_1123_DB(c);
10  exit when nr=0;
11  dbms_hs_passthrough.get_value@DG4MSQL_EMGTW_1123_DB(c,1,val);
12  dbms_output.put_line(val);
13  end loop;
14  dbms_hs_passthrough.close_cursor@DG4MSQL_EMGTW_1123_DB(c);
15  end;
16  /
SQL_Latin1_General_CP1_CI_AS
PL/SQL procedure successfully completed.
Just in case you have a procedure that returns the correct data type you have to make sure the gateway is configured correctly which means the parameter
HS_FDS_PROC_IS_FUNC needs to be set to TRUE and the function you want to call is listed in the HS_CALL_NAME parameter.
Here for a userdefined function I have to specify:
HS_FDS_PROC_IS_FUNC=TRUE
HS_CALL_NAME = "dbo.fx_SumTwoValues"
and then  the udf based select:
SQL> SELECT "dbo"."fx_SumTwoValues"@DG4MSQL_EMGTW_1123_DB('7','8') AS SumOfTwoValues from "dummy"@DG4MSQL_EMGTW_1123_DB;
SUMOFTWOVALUES
            15
- Klaus