Re: slowest tap tests - split or accelerate?

On Mon, Jan 17, 2022 at 2:57 PM Andres Freund <andres(at)anarazel(dot)de> wrote:
> I wonder if there's something explaining why pg_verifybackup is greatly slowed
> down by sha224 but not crc32c, but the server's runtime only differs by ~20ms?
> It seems incongruous that pg_basebackup, with all the complexity of needing to
> communicate with the server, transferring the backup over network, and *also*
> computing checksums, takes as long as the pg_verifybackup invocation?

I guess there must be something explaining it, but I don't know what
it could be. The client and the server are each running the checksum
algorithm over the same data. If that's not the same speed then .... I
don't get it. Unless, somehow, they're using different implementations
of it?

> I've occasionally pondered caching initdb results and reusing them across
> tests - just the locking around it seems a bit nasty, but perhaps that could
> be done as part of the tmp_install step. Of course, it'd need to deal with
> different options etc...

It's a thought, but it does seem like a bit of a pain to implement.

--
Robert Haas
EDB: http://www.enterprisedb.com