RE: Query started getting 1722 error - interesting explanation why

Jay,  

    Did that varchar2 have numbers only in it before it stopped working and then picked up one with an alpha character? I've seen that one more than I care to remember.

From: oracle-l-bounce_at_freelists.org
[mailto:oracle-l-bounce_at_freelists.org] On Behalf Of JayMiller_at_TDWaterhouse.com
Sent: Friday, September 09, 2005 2:16 PM To: oracle-l_at_freelists.org
Subject: Query started getting 1722 error - interesting explanation why

I got a call from a developer the other week complaining that a query in QA had started giving an ora-1722. It had worked fine for several months and the identical query was working fine in production.  

Select count(1)

from prod.job_profile jp

where step_id < 9999

and not exists (select 'x' from prod.job_log jl

                where jl.job_id = jp.job_id

                and ( jl.status in ('C', 'EI') )

                and  jl.batch_id in (select to_number(text_value)

                                     from prod.batch_parameter

                                     where name = 'BATCH_ID'));

 

Investigating confirmed this, along with the fact that the query was comparing a string (jl.batch_id) with a number (to_number(text_value)). But why did it suddenly stop working and why did it still work in production?  

Comparing explain plans between QA and production I saw that they were different (statistics had changed during QA testing). The query that failed was using an index on jl.batch_id.  

Apparently Oracle automatically took care of converting the string to a number *unless* the number was being used to access an index on the varchar2 column. Interesting behavior. I can see why it might work that way but it's certainly not intuitive.  

Of course explaining this to the developer took quite a while. "It worked before, why shouldn't it work now? What's wrong with Oracle?"  

Oracle 9.2.0.6    

Jay Miller

Sr. Oracle DBA  

.

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