Re: Trying out read streams in pgvector (an extension)

On Tue, Dec 9, 2025 at 4:42 PM Melanie Plageman
<melanieplageman(at)gmail(dot)com> wrote:
>
> > 1. read_stream_resume() as before, but with a new explicit
> > read_stream_pause(): if a block number callback would like to report a
> > temporary lack of information, it should return
> > read_stream_pause(stream), not InvalidBlockNumber. Then after
> > read_stream_resume(stream) is called, the next
> > read_stream_next_buffer() enters the lookahead loop again. While
> > paused, if the consumer drains all the existing buffers in the stream
> > and then one more, it will receive InvalidBuffer, but if the _resume()
> > call is made sooner, the consumer won't ever know about the temporary
> > lack of buffers in the stream.

I ended up committing read_stream_resume() in 38229cb905165fe but
without the tests because 1f6f200cab67e6, which added other read
stream tests, was imminent. I'd like to add the read_stream_resume()
test back now -- especially because we didn't end up adding another
user of read_stream_resume() in this release.

Attached 0001 is the test Thomas wrote ported over to be in the new
0004_read_stream.pl. It uses asserts instead of comparing output of
the SQL function to expected output, so I included a potential
alternative version of it in 0002 that uses that pattern. Note that
0002 is a diff from 0001, not an independent alternative patch. I
think the test needs more work either way, but I wanted to get the
ball rolling.

- Melanie