Re: Database exceptions

["Ilya A. Volynets-Evenbakh" <ilya@total-knowledge.com>]

OK. Sounds good. We need to document it somewhere on the wiki.
(I presume "single procedure per modification" is currently the case for UU)

   Ilya.

Alexey Parshin wrote:
> I'd not suggest such transactions. Any data modifications in UU are 
> made through the stored procedures. The ideal case is the only one 
> stored procedure performing all the required data modifications. The 
> main idea is to keep the transaction as short as possible. This is 
> needed since every db resource modified within the transaction is 
> locked till the end of transaction. A single stored procedure called 
> to do all the modifications does the job the fastest and safest way.
>
> The explicit transactions are handled correctly by CTransaction 
> object. If defined as auto variable and goes out of scope (upon the 
> exception) it automatically rolls back ancommitted transaction. 
> However, the only reason for using explicit transaction handling is 
> using several queries executed within transaction. This is generally 
> ineffective but may be needed in some perverted situations (like 
> Slonic file operations, for instance).
>
> 2008/12/23 Ilya A. Volynets-Evenbakh <ilya@total-knowledge.com 
> <mailto:ilya@total-knowledge.com>>
>
>     Thanks.
>
>     What do you think about making explicit transactions, starting one
>     when connection is retrieved from the pool, and ending it when it
>     is released back? (Question here is: how do we decide if we need
>     to commit the transaction or roll it back. Does explicit transaction
>     get rolled back if an exception is thrown by a stored proc?)
>
>     Ilya.
>
>     Alexey Parshin wrote:
>
>         Ilya,
>
>         The database exceptions are thrown in several different
>         situations. This includes both read-only data access and data
>         modifications. Normally, exceptions thrown by the stored
>         procedures (any data access is done through stored procs) are
>         re-thrown by sptk::CQuery as sptk::CException.
>
>         By the definition, any call of the stored procedure is a
>         transaction. If the exception is thrown from within the stored
>         procedure, the transaction is terminated and rolled back by PG
>         server, to the state before the procedure call. If no
>         exceptions are thrown, stored proc exits and transaction is
>         committed by PG server.
>
>         The exception from the above rule is the manual transaction
>         start (using CTransaction) and performing several procedure
>         calls followed by explicit commit (rollback happens on
>         exceptions), but this isn't used in UU at this point.
>
>         2008/12/23 Ilya A. Volynets-Evenbakh <ilya@total-knowledge.com
>         <mailto:ilya@total-knowledge.com>
>         <mailto:ilya@total-knowledge.com
>         <mailto:ilya@total-knowledge.com>>>
>
>
>            Alexey,
>
>            I have a few questions regarding UU database.
>
>            What happens if database exception is thrown in UU?
>            Does anything rollback? To what point?
>            Also, when does commit of a transaction happen?
>
>              Ilya.
>
>
>
>
>         -- 
>         Alexey Parshin,
>         http://www.sptk.net
>
>
>
>
>
> --
> Alexey Parshin,
> http://www.sptk.net