RE: UDF in WHERE clause causes an odd execution plan

Vlad Arkhipov wrote:

> CREATE TABLE GIS2.SERVICES (
>     ID INTEGER NOT NULL DEFAULT SERIAL(1) PRIMARY KEY,
>     CODE VARCHAR(10) NOT NULL UNIQUE
> )
> 
> CREATE TABLE GIS2.SERVICE_DATA (
>     ID INTEGER NOT NULL DEFAULT SERIAL(1) PRIMARY KEY
> )
> 
> CREATE FUNCTION GIS2.GETSERVICEID (
>     RESID CHAR(10))
> RETURNS INTEGER
> AS
>     VAR ID INTEGER;
> 
>     TRY
>         SELECT ID INTO :ID FROM GIS2.SERVICES WHERE CODE = :RESID;
>     CATCH
>         IF $rc <> 100 THEN STOP($rc, 'unexpected error')
>         ELSE RETURN NULL;
> 
>     RETURN ID;
> 
> EXPLAIN
> SELECT ID
> FROM GIS2.SERVICE_DATA
> WHERE ID = 1
> 
>  OWNER     TABLENAME      COLUMN_OR_INDEX     
> STRATEGY                                PAGECOUNT   
>  --------  -------------  ------------------  
> --------------------------------------  ------------
>  GIS2      SERVICE_DATA                       EQUAL CONDITION FOR 
> KEY                        542  
>                           ID                       (USED KEY 
> COLUMN)                              
>            JDBC_CURSOR_4                         RESULT IS 
> NOT COPIED , 
> COSTVALUE IS           1  
> 
> EXPLAIN
> SELECT ID
> FROM GIS2.SERVICE_DATA
> WHERE ID = GIS2.GETSERVICEID('12345')
> 
> OWNER     TABLENAME      COLUMN_OR_INDEX     
> STRATEGY                                PAGECOUNT   
>  --------  -------------  ------------------  
> --------------------------------------  ------------
>  GIS2      SERVICE_DATA                       TABLE 
> SCAN                                      35  
>            JDBC_CURSOR_2                         RESULT IS 
> NOT COPIED , 
> COSTVALUE IS          35  
> 
> Tested on MaxDB 7.6.00.16 - 016-123-109-428.
 

Hi,

the optimizer doesn't support such conditions with user defined functions by now.
We have to discuss if we will support it in the future.
If your example comes from a real application and is not only a simplified example
you could use a sub select instead.
Example:

EXPLAIN
SELECT ID
FROM GIS2.SERVICE_DATA
WHERE ID = (SELECT ID FROM GIS2.SERVICES WHERE CODE = '12345')

Kind regards
Holger


Holger Becker
MaxDB&liveCache
SAP AG
www.sap.com
Sitz der Gesellschaft/Registered Office: Walldorf, Germany
Vorstand/SAP Executive Board: Henning Kagermann (Sprecher/CEO),  Léo Apotheker, Werner Brandt, Claus Heinrich, Gerhard Oswald, Peter Zencke
Vorsitzender des Aufsichtsrats/Chairperson of the SAP Supervisory Board: Hasso Plattner 
Registergericht/Commercial Register Mannheim No HRB 350269

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