Hi,
On 2024-04-10 16:50:44 -0400, Melanie Plageman wrote:
> This brings up a question about the prefetching. We never had to have
> this discussion for sequential scan streaming read because it didn't
> (and still doesn't) do prefetching. But, if we push the streaming read
> code down into the heap AM layer, it will be doing the prefetching.
> So, do we remove the prefetching from acquire_sample_rows() and expect
> other table AMs to implement it themselves or use the streaming read
> API?
The prefetching added to acquire_sample_rows was quite narrowly tailored to
something heap-like - it pretty much required that block numbers to be 1:1
with the actual physical on-disk location for the specific AM. So I think
it's pretty much required for this to be pushed down.
Using a read stream is a few lines for something like this, so I'm not worried
about it. I guess we could have a default implementation for block based AMs,
similar what we have around table_block_parallelscan_*, but not sure it's
worth doing that, the complexity is much lower than in the
table_block_parallelscan_ case.
Greetings,
Andres