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" <[EMAIL PROTECTED]>
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" <[EMAIL PROTECTED]>
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
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> Author: Daniel Wisser
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