Re: pg_freespacemap question

Mark Kirkwood <markir@paradise.net.nz> writes:
>> Good points! I had not noticed this test case. Probably NULL is better 

> Would setting it to 'BLCKSZ - (fixed index header stuff)' be better, 

No, I don't think so, because that will just make it harder to recognize
what's what (remember that BLCKSZ isn't really a constant, and the index
overhead is not the same for all AMs either).  The point here is that
for indexes the FSM tracks whole-page availability, not the amount of
free space within pages.  So I think NULL is a reasonable representation
of that.  Using NULL will make it easy to filter the results if you want
to see only heap-page data or only index-page data, whereas it will be
very hard to do that if the view adopts an ultimately-artificial
convention about the amount of available space on an index page.
        regards, tom lane