Re: Is possible to use Prepare/Execute inside a function?

On 15 Dec 2010, at 18:10, felipe@informidia.com.br wrote:

> Hello, I'm having problems with a function after the postgres server has been upgraded to 8.3.10 (I used 8.3.7). I
didsome testing and found some strange situations. 

There shouldn't be any differences when upgrading between minor versions, they are bug-fix releases. If you found any,
thenthat's either a bug in Postgres or a bug in your code. 

To find out which, could you elaborate on how you performed said upgrade? Did you dump/restore your database or did you
upgradethe binaries in place? 
Were both versions compiled with the same settings (eg. integer datetimes)?

If you used dump/restore, are you sure your restore was successful and that no part of your data or code resulted in an
errorand therefore wasn't restored? 

Also, what platform are you on? Is this Windows, some kind of Linux distribution, or what? What version?

> ------------------------------------------------------------------------------------------------------------
> -- not work with the direct call function (worked before the upgrade)
> select f_rodar_reportagem(44359, 193097);

First of all, what do you mean by "not work"? If you get an error, please post it.

What's the implementation of this function? It's possible that you were relying on a bug that got fixed between said
releases.
A direct function call should just work, so something strange is going on here. Without the function body we can't tell
though.

It's probably best to create a simple test case where you call a function directly (using select) and extend that
towardsyour problem function's implementation until you manage to trigger the issue. If that doesn't work, you can
alwayspost the body of your function (unless you have reasons not to, of course). 

> -- not work with the call by the trigger (a trigger calls a function and it calls f_rodar_reportagem using select and
workedbefore the upgrade)  
> update repesportesmt set
>        estado = '1'
> where idrepesportesmt = 44359;

I suspect this has the same result as your earlier query? If not, please post the error message.

> -- WORK using Prepare/Execute
> prepare rodar(int, int) as select f_rodar_reportagem($1, $2);
> execute rodar(44359, 193097);

That is really strange and it's what made me think you may have been relying on a bug. I think the main difference
betweena direct statement and a prepared statement is that the prepared statement stores the query plan at preparation
time,while the direct statement could execute different plans depending on the data. Apparently some of those plans
causeyour problem. 
Posting them here may help as well.

If you look at the query plans for both, what do you see? Can you find any data with which the direct statement does
work?

> I do not understand why not working after upgrade, but worked with prepare/execute, so I tried to use inside a
functionbut did not work. 
>
> -- got error in this line on params
> prepare rodar(int, int) as select f_rodar_reportagem($1, $2);

Again, post the error message please.

Alban Hertroys

--
If you can't see the forest for the trees,
cut the trees and you'll see there is no forest.


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