Обсуждение: read commited

The first part in the doc about concurrency with Read Commited
transactions (12.2.1 in devel doc) it says:

| Read Committed is the default isolation level in PostgreSQL.
| When a transaction runs on this isolation level, a SELECT query
| sees only data committed before the query began; it never sees
| either uncommitted data or changes committed during query
| execution by concurrent transactions.

And that describes serializable transactions. Read committed means that
you _can_ see changes commited by other transactions.

This have been in the manual since the 6.x days, which is very strange.
Either I'm reading this wrong in some way, or the manual have been wrong
since the start of time (or something)..

--
/Dennis

=?ISO-8859-1?Q?Dennis_Bj=F6rklund?= <db@zigo.dhs.org> writes:
> The first part in the doc about concurrency with Read Commited
> transactions (12.2.1 in devel doc) it says:
> | Read Committed is the default isolation level in PostgreSQL.
> | When a transaction runs on this isolation level, a SELECT query
> | sees only data committed before the query began; it never sees
> | either uncommitted data or changes committed during query
> | execution by concurrent transactions.

> And that describes serializable transactions.

No, it doesn't.  The critical phrase here is "data committed before the
*query* began" ... not "data committed before the *transaction* began".

            regards, tom lane

On Mon, 25 Aug 2003, Tom Lane wrote:

> No, it doesn't.  The critical phrase here is "data committed before the
> *query* began" ... not "data committed before the *transaction* began".

Aah, of course, it says query. Thanks (again).

--
/Dennis