Re: Using read stream in autoprewarm

Hi,

On 2025-03-29 16:09:56 -0400, Melanie Plageman wrote:
> I've started looking at this version. What I don't like about this
> structure is that we are forced to increment the position in the array
> of BlockInfoRecords in both the callback and the main loop in
> autoprewarm_database_main(). There isn't a way around it because we
> have to return control to the user when we encounter a new relation
> (we can't close the relation and destroy the read stream in the
> callback). And in the main loop in autoprewarm_database_main(), we may
> fail to open the next relation and then need to keep advancing the
> position in the array of BlockInfoRecords.
>
> It isn't just that we have to advance the position in both places --
> we also have to have a special case for the first block. All in all,
> given that in the current read stream API, a single stream must only
> concern itself with a single relation, fork combo, I think there is no
> elegant way to deal with this in autoprewarm.

How about having an iterator function operating on a pointer to iterator state
that's used both by the main loop and the read stream callback? If the
iterator reaches the next relation, it returns InvalidBlockNumber and the main
loop starts the next stream?

Greetings,

Andres Freund