Re: Free space mapping (was Re: Multi-Versions and Vacuum)

Tom Lane wrote:

>It doesn't need a lot of examination in my mind: the cause is surely
>growth of the index on the toast table.  Since that index's first column
>is the OID assigned to the toast item, the range of indexed values tends
>to shift over time, causing the leftmost parts of the index btree to
>become sparsely populated and eventually empty.  Since we don't
>currently have code to collapse out empty pages in a btree, the index
>grows during continued update activity, even if the total amount of data
>you're storing isn't growing.  This is quite unrelated to the free space
>map --- indexes don't use the FSM.
>
>  
>
hmmm, good point - I thought the toast table was growing too, but I will 
check this.

regards

Mark