Re: pg_freespacemap question

Tatsuo Ishii <ishii@sraoss.co.jp> writes:
>> Peter Eisentraut wrote:
>> 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.

Right, which is correct because free space is associated with physical
files not logical relations.  (TRUNCATE, CLUSTER, etc will completely
change the freespace situation for a rel, but they don't change its OID.)

I do agree with the comment that the column order seems nonintuitive;
I'd expect database/tablespace/relfilenode/blocknumber, or possibly
tablespace first.  The names used for the columns could do with
reconsideration.  And I don't see the point of the blockid column at
all.
        regards, tom lane