Обсуждение: Transaction: Begin, Lock

Hi,

I have two questions about transactions.
This is part of my C code.

EXEC SQL CONNECT TO ...
for (i=2; i<x: i++) { strncpy(oid_c, entries[i].val, 10);  /* get oid */ oid_rec = atoi(oid_c); EXEC SQL BEGIN WORK;
EXECSQL DELETE FROM phonebook          WHERE oid = :oid_rec; EXEC SQL COMMIT WORK;
 
}
EXEC SQL DISCONNECT;

1. Why i get the following message when I run this code?
NOTICE: BeginTransactionBlock and not in default state

2. How should I lock the table phonebook during this transaction?

Thank you,

-Margarita
-------------------------------
Margarita Barvinok
System Administrator II
University of Michigan
Department of Biology
-------------------------------

On Mon, Sep 13, 1999 at 10:58:43AM -0400, Margarita Barvinok wrote:
> EXEC SQL CONNECT TO ...
> for (i=2; i<x: i++) {
>   strncpy(oid_c, entries[i].val, 10);  /* get oid */
>   oid_rec = atoi(oid_c);
>   EXEC SQL BEGIN WORK;
>   EXEC SQL DELETE FROM phonebook
>            WHERE oid = :oid_rec;
>   EXEC SQL COMMIT WORK;
> }
> EXEC SQL DISCONNECT;
> 
> 1. Why i get the following message when I run this code?
> NOTICE: BeginTransactionBlock and not in default state

I take it you did not use 'ecpg -t' did you? The normal situation is that
ecpg creates a auto-transaction mode, i.e. a transaction is started
automatically. You only need to issue a COMMIT once you finish your
transaction resp. a ROLLBACK if you want to cancel it. 

So you tell the backend to start a transaction while already inside a
transaction. And that cannot work. 

You can either just remove the BEGIN WORK statement or you always give
option '-t' to ecpg.

> 2. How should I lock the table phonebook during this transaction?

Why do you need that? You do not need an explicit lock for the delete to
work.

Michael
-- 
Michael Meskes                         | Go SF 49ers!
Th.-Heuss-Str. 61, D-41812 Erkelenz    | Go Rhein Fire!
Tel.: (+49) 2431/72651                 | Use Debian GNU/Linux!
Email: Michael@Fam-Meskes.De           | Use PostgreSQL!

Michael, thank you very much.
I didn't know this.

-Margarita

On Tue, 14 Sep 1999, Michael Meskes wrote:

> > 1. Why i get the following message when I run this code?
> > NOTICE: BeginTransactionBlock and not in default state
> 
> I take it you did not use 'ecpg -t' did you? The normal situation is that
> ecpg creates a auto-transaction mode, i.e. a transaction is started
> automatically. You only need to issue a COMMIT once you finish your
> transaction resp. a ROLLBACK if you want to cancel it. 
> 
> So you tell the backend to start a transaction while already inside a
> transaction. And that cannot work. 
> 
> You can either just remove the BEGIN WORK statement or you always give
> option '-t' to ecpg.
> 
> > 2. How should I lock the table phonebook during this transaction?
> 
> Why do you need that? You do not need an explicit lock for the delete to
> work.
> 
> Michael
> -- 
> Michael Meskes                         | Go SF 49ers!
> Th.-Heuss-Str. 61, D-41812 Erkelenz    | Go Rhein Fire!
> Tel.: (+49) 2431/72651                 | Use Debian GNU/Linux!
> Email: Michael@Fam-Meskes.De           | Use PostgreSQL!
> 

-------------------------------
Margarita Barvinok
System Administrator II
University of Michigan
Department of Biology
-------------------------------