Re: pg_freespacemap question

Tatsuo Ishii wrote:
>>Peter Eisentraut wrote:
>>
>>>Am Dienstag, 7. März 2006 15:09 schrieb Tatsuo Ishii:
>>>
>>>>test=# select * from pg_freespacemap where blockfreebytes = 0;
>>>> blockid | relfilenode | reltablespace | reldatabase | relblocknumber | blockfreebytes
>>>>---------+-------------+---------------+-------------+----------------+---------------- 
>>>>      25 |        2619 |          1663 |       16403 |              0 |              0
>>>>      63 |        2619 |          1663 |       16384 |             10 |              0
>>>>(2 rows) 
>>>
>>>I've never heard of this thing before but is this column order supposed to make sense?
>>
>>I have another question -- why is the view showing relfilenode and
>>reltablespace?  I imagine it should be showing the relation Oid instead.
> 
> 
> I guess that's because FSM keeps those info, not relation oid.
> 
> 
>>And what is this "blockid" thing?
> 
> 
> from README.pg_freespacemap:
> 
>    blockid        |                      | Id, 1.. max_fsm_pages
> 

I put that in as a bit of a sanity check - to see if the view was 
picking up all the fsm pages - guess it is a bit redundant now.

> BTW, I found the answer to my question myself by reading the source
> code: if that's an index, then blockfreebytes is explicitly set to 0.
> I suggest that this should be noted in the README and in this case
> blockfreebytes is better to set to NULL, rather than 0.
> 

Good points! I had not noticed this test case. Probably NULL is better 
than zero.


I'll look into making these changes! (good to see people checking the 
view out).

Cheers

Mark