Re: WIP: Avoid creation of the free space map for small tables

On 10/7/18, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> wrote:
> John Naylor <jcnaylor(at)gmail(dot)com> writes:
>> On 10/6/18, Thomas Munro <thomas(dot)munro(at)enterprisedb(dot)com> wrote:
>>> On Sat, Oct 6, 2018 at 7:47 AM John Naylor <jcnaylor(at)gmail(dot)com> wrote:
>>>> A while back, Robert Haas noticed that the space taken up by very
>>>> small tables is dominated by the FSM [1]. Tom suggested that we could
>>>> prevent creation of the FSM until the heap has reached a certain
>>>> threshold size [2]. Attached is a WIP patch to implement that.
>
> BTW, don't we need a similar hack for visibility maps?

The FSM is the bigger bang for the buck, and fairly simple to do, but
it would be nice to do something about VMs as well. I'm not sure if
simply lacking a VM would be as simple (or as free of downsides) as
for the FSM. I haven't studied the VM code in detail, however.

-John Naylor