Subject Re: [firebird-support] MAKE 'EXECUTE STATEMENT' USE INDEX
Author Mr. John
Post date 2015-08-19T07:26:57Z
Hi,thanks for your answer

I remove pCondition variable and use :F3 insead (:F3=NULL means no F3  field condition,else F3 condition)and I simply have

WHERE FIEL1=:F1 AND FIEL2=:F2 AND    (FIEL3=:F3 OR :F3 IS NULL)     INTO .. DO ..

now index is used if I call 
SELECT * FROM MYPROC(...)
but I use it in other procedures,no join on it just simply SELECT .. FROM MYPROC(...) in this case I can see in the plan :
...(MYPROC NATURAL)...
very strange,I have to fix it because this query takes about 20 min

thanks!






From: "setysvar setysvar@... [firebird-support]" <firebird-support@yahoogroups.com>
To: firebird-support@yahoogroups.com
Sent: Tuesday, August 18, 2015 8:03 PM
Subject: Re: [firebird-support] MAKE 'EXECUTE STATEMENT' USE INDEX

 
Den 18.08.2015 16:59, skrev 'Mr. John' mr_johnmr@... [firebird-support]:


HI,in SP I have this query

  FOR EXECUTE STATEMENT 'SELECT SUM(CANT)  FROM TABLE1 WHERE FIEL1='||:F1||' AND FIEL2='||:F2|| IIF(:pCondition=1,' AND FIEL3='||:F3,'')  INTO .. DO ..
 
 TABLE1 PK =FIELD1,FIELD2,FIELD3

 running the query gives a NATURAL PLAN

How to make it use the index?

Index is used if I change to:
    FOR SELECT SUM(CANT)  FROM TABLE1 WHERE FIEL1=:F1 AND FIEL2=:F2 AND FIEL3=:F3 INTO .. DO ..
but this way I can't use the IIF condition that I need

thanks!

Why would you need an IIF condition? What about

FOR SELECT SUM(CANT)  FROM TABLE1 WHERE FIEL1=:F1 AND FIEL2=:F2 AND (FIEL3=:F3 or cast(:pCondition as SmallInt) is distinct from 1) INTO .. DO ..

That could at least use an index for FIEL1 and FIEL2 (if they are the first two fields in your PK, that index could be used). Now, in some cases the index may have poor selectivity so that it still chooses natural (you didn't say whether "FOR SELECT SUM(CANT)  FROM TABLE1 WHERE FIEL1=:F1 AND FIEL2=:F2 INTO .. DO .." uses an index or not). If so, the only way to use the index would be to use IF in your procedure and two separate queries, the index being used if you run the query comparing with FIEL3, but no index used when you run the query with only FIEL1 and FIEL2.

I've seen Dmitry Yemanov answer a different question (that may or may not be similar to yours) with repeating the first part and that could possibly translate to:

FOR SELECT SUM(CANT)  FROM TABLE1 WHERE (FIEL1=:F1 AND FIEL2=:F2 AND FIEL3=:F3) or
(FIEL1=:F1 AND FIEL2=:F2 AND cast(:pCondition as SmallInt) is distinct from 1)

I never quite understood why I saw a similar statement to this, but I assume it doesn't hurt trying if my first suggestion fails.

Set