On 13.09.2011 20:57, Stefan Keller wrote:
Interesting debate.
Indeed.
2011/9/13 Marti Raudsepp<marti@xxxxxxxxx>:
Yes, every BEGIN/EXCEPTION block creates a subtransaction -- like a
SAVEPOINT it can roll back to in case of an error.
Are you sure? In theory I always understood that there are no
"subtransactions".
What theory are you referring to?
In fact when looking at the docs there is chapter 39.6.6. saying "By
default, any error occurring in a PL/pgSQL function aborts execution
of the function, and indeed of the surrounding transaction as well.
You can trap errors and recover from them by using a BEGIN block with
an EXCEPTION clause."
(http://www.postgresql.org/docs/current/interactive/plpgsql-control-structures.html
)
So the doc isn't totally explicit about this. But whatever: What would
be the the function of a subtransaction? To give the possibility to
recover and continue within the surrounding transaction?
I find this pretty explicit:
It is important not to confuse the use of BEGIN/END for grouping
statements in PL/pgSQL with the similarly-named SQL commands for
transaction control. PL/pgSQL's BEGIN/END are only for grouping; they do
not start or end a transaction. Functions and trigger procedures are
always executed within a transaction established by an outer query —
they cannot start or commit that transaction, since there would be no
context for them to execute in. However, a block containing an EXCEPTION
clause effectively forms a subtransaction that can be rolled back
without affecting the outer transaction. For more about that see Section
38.6.5.
http://www.postgresql.org/docs/8.4/interactive/plpgsql-structure.html
Cheers
robert
--
Sent via pgsql-performance mailing list (pgsql-performance@xxxxxxxxxxxxxx)
To make changes to your subscription:
http://www.postgresql.org/mailpref/pgsql-performance
