Re[2]: newbie question - still: please help

Daniel,

    After some of the younger folks in the audience have had a say, Let's let the "old fart" have one.

    While on the one hand I can see what your DBA is croaking on, I can also see where you are too. Your approach is easy to code, but can wreck hell on the database especially if each statement requires a full table scan.

    With the DBA's view your update statement turns into a select, followed by a delete, and then an insert after you've processed the file. Damn, that's a lot of work for a simple update and who's to say that the process handling the interim data file is bug free as well. As Scotty in Star Trek 3 said "The more you overtake the pluming, the easier it is to stop up the drain". What happens when part of your application needs the data record in the middle of your update? Or the business logic changes? Very convoluted pluming, many tight drains.

    But, having a loop as you do that sets a value to a constant for several document id's in series, come on!! Why not put those id's into a global temp table (or suitable substitute) and then use an "UPDATE ISIS_DOCAR SET STATUS = 2000 WHERE ID in (select id from temp_table);" One statement, several thousand rows updated. Simple pluming, one very large drain.

    An interim solution might be to select your data, which obviously you did to fill in 'n', with the "for update clause". Then your update changes into "UPDATE ISIS_DOCAR SET STATUS = 2000 WHERE current of cursor x;" Less io on the system, same result. The pluming gets a little more complicated, but the drain is still large & free flowing.

Dick Goulet
Senior Oracle DBA & Oracle Certified 8i DBA Vicor Corporation

____________________Reply Separator____________________
Author: "Tim Gorman" <Tim_at_SageLogix.com>
Date:       1/13/2003 9:40 AM

Daniel,

Your gut reaction is right on-target. It is always a struggle to keep certain folks from killing the entire village while trying to cure a single case of the sniffles. What's worse is that such folks are usually quite bright and talented. After, very few mediocre folks can either cure the sniffles or kill entire villages... ;-)

Longer response: This is a common argument that eventually distills down to something like "I don't need a stupid database engine to do this. I can do it all in (choose one): C, C++, Perl, shell script, Java." What the person has to realize is that those 'stupid database engines' started out as lone programmers doing what he is describing but then running into problems such as transaction recoverability (aka rollback), concurrency, and its close cousin read-consistency. Oh yeah, and then there is also what my good friend Gary once called "DFB" or "diddly file build-up" (i.e. an excess of "diddly files" in a file-system), which very few people see up front but invariably grows to dominate such approaches. After some decades of effort by thousands of developers and designers (very few of whom are stupid), what results is the modern database engine. Such people who think they can outperform database engines without losing such crucial features do not have any sense of humility about their place in the world. Ask him to skim through Gray and Reuter's "Principles of Transaction Processing" to gain some of that humility...

Shorter response: look into using PL/SQL bulk-bind operations (i.e. FORALL, BULK COLLECT, etc) instead of one-row-at-a-time processing.

I suspect the latter approach will be more effective... :-)

Hope this helps...and keep up the good work!

-Tim

• Original Message ----- To: "Multiple recipients of list ORACLE-L" <ORACLE-L_at_fatcity.com> Sent: Monday, January 13, 2003 9:14 AM

> hi!
>
> a DBA inteds to speed up a script that is looping and
> sending hundred thousands of sequential update statements like:
>
> UPDATE ISIS_DOCAR SET STATUS = 2000 WHERE ID = n;
>
> he suggests copying the table to a file, change it and then
> load it into the DB again. i am strongly convinced that this
> is nonsense.
>
> what is the best way to go for a script like this, doing tons of
> updates? (except convincing him to swith to sell burgers)
>
>
> thx
> daniel
> --
> Please see the official ORACLE-L FAQ: http://www.orafaq.net
> --
> Author: Daniel Wisser
> INET: daniel.wisser_at_isis-papyrus.com
>
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  INET: Tim_at_SageLogix.com

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