Thread: Question about ALTER TABLE SET TABLESPACE locing behaviour

Does ALTER TABLE SET TABLESPACE lock the table while copying data to new
location ?

If so, then does it lock the whole table, or just the tuples belonging
to currently copied 1G file ?

----------------
Hannu

Hannu Krosing <hannu@skype.net> writes:
> Does ALTER TABLE SET TABLESPACE lock the table

It had better ... see nearby discussion about relaxing locking for
TRUNCATE.  Exactly the same problem that at commit we'd be cutting
the ground out from under any concurrent query.
        regards, tom lane

Ühel kenal päeval, K, 2006-02-01 kell 18:08, kirjutas Tom Lane:
> Hannu Krosing <hannu@skype.net> writes:
> > Does ALTER TABLE SET TABLESPACE lock the table
> 
> It had better ... see nearby discussion about relaxing locking for
> TRUNCATE.  

Is it some recent disussion ?

> Exactly the same problem that at commit we'd be cutting
> the ground out from under any concurrent query.

Can't we just keep READ locks and reopen the datafile from its new
location before releasing it ?

Does our shared memory page cache implementation track logical or
physical pages ? If it's just logical pages, then moving the physical
storage around below should not affect it. 

Of course there are problems with WAL/PITR which *have* to deal with
physical storage, but this should be mostly unrelated.

--------------
Hannu

Hannu Krosing wrote:

>Ühel kenal päeval, K, 2006-02-01 kell 18:08, kirjutas Tom Lane:
>  
>
>>Hannu Krosing <hannu@skype.net> writes:
>>    
>>
>>>Does ALTER TABLE SET TABLESPACE lock the table
>>>      
>>>
>>It had better ... see nearby discussion about relaxing locking for
>>TRUNCATE.  
>>    
>>
>
>Is it some recent disussion ?
>  
>
it is "[PERFORM] partitioning and locking problems" (on the performance 
list)

Regards,