Обсуждение: AW: BLERe: AW: AW: relation ### modified while in use

> > > Are there many applications which have many SELECT statements(without
> > > FOR UPDATE) in one tx ?
> >
> > Why not ?
> >
> It seems to me that multiple SELECT statements in a tx has little
> meaning unless the tx is executed in SERIALIZABLE isolation level.

E.g. a table is accessed multiple times to select different data
in an inner application loop. No need for serializable here.

Andreas

Zeugswetter Andreas SB wrote:

> > > > Are there many applications which have many SELECT statements(without
> > > > FOR UPDATE) in one tx ?
> > >
> > > Why not ?
> > >
> > It seems to me that multiple SELECT statements in a tx has little
> > meaning unless the tx is executed in SERIALIZABLE isolation level.
>
> E.g. a table is accessed multiple times to select different data
> in an inner application loop. No need for serializable here.
>

And seems no need to execute in one tx.
Hmm,we seems to be able to call a cleanup procedure
internally which is equivalent to 'commit' after each
consecutive read-only statement.  Is it a problem ?

Regards.
Hiroshi Inoue

Hello,
anyone thought about implementing two-phase commit to
be able to support distributed transactions ?
I have no clue how complex it would be, someone knows ?

devik

At 18:31 24/10/00 +0900, Hiroshi Inoue wrote:
>
>
>Zeugswetter Andreas SB wrote:
>
>> > > > Are there many applications which have many SELECT statements(without
>> > > > FOR UPDATE) in one tx ?
>> > >
>> > > Why not ?
>> > >
>> > It seems to me that multiple SELECT statements in a tx has little
>> > meaning unless the tx is executed in SERIALIZABLE isolation level.
>>
>> E.g. a table is accessed multiple times to select different data
>> in an inner application loop. No need for serializable here.
>>
>
>And seems no need to execute in one tx.
>Hmm,we seems to be able to call a cleanup procedure
>internally which is equivalent to 'commit' after each
>consecutive read-only statement.  Is it a problem ?

I have not followed the entire thread, but if you are in a serializable OR
repeatable-read transaction, I would think that read-only statements will
need to keep some kind of lock on the rows they read (or the table).


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Philip Warner wrote:

> At 18:31 24/10/00 +0900, Hiroshi Inoue wrote:
> >
> >
> >Zeugswetter Andreas SB wrote:
> >
> >> > > > Are there many applications which have many SELECT statements(without
> >> > > > FOR UPDATE) in one tx ?
> >> > >
> >> > > Why not ?
> >> > >
> >> > It seems to me that multiple SELECT statements in a tx has little
> >> > meaning unless the tx is executed in SERIALIZABLE isolation level.
> >>
> >> E.g. a table is accessed multiple times to select different data
> >> in an inner application loop. No need for serializable here.
> >>
> >
> >And seems no need to execute in one tx.
> >Hmm,we seems to be able to call a cleanup procedure
> >internally which is equivalent to 'commit' after each
> >consecutive read-only statement.  Is it a problem ?
>
> I have not followed the entire thread, but if you are in a serializable OR
> repeatable-read transaction, I would think that read-only statements will
> need to keep some kind of lock on the rows they read (or the table).
>

Currently read-only statements keep AccessShareLock on the table
(not on the rows) until the end of the statement and none objects
to it.  What we've discussed is whether we should keep the lock
until the end of tx or not in read committed mode.

Regards.
Hiroshi Inoue