Re: Statistics Import and Export

On Wed, 2025-04-02 at 21:26 -0500, Nathan Bossart wrote:

> Okay, here is an updated patch set.

> * Besides custom format calling WriteToc() twice to update the data
>   offsets, tar format ... even if it did, the worst case is that
> the
>   content of restore.sql (which isn't used by pg_restore) would be
>   different.  I noticed some past discussion that seems to suggest
> that
>   this format might be a candidate for deprecation [0], so I'm not
> sure
>   it's worth doing anything fancier.

I agree that the risk for tar format seems much lower.

> * Our batching code assumes that stats entries are dumped in TOC
> order,
>

...

> I propose moving all
>   stats entries in SECTION_POST_DATA to RESTORE_PASS_POST_ACL, which
>   ensures that we always dump stats in TOC order.  One convenient
> side
>   effect of this change is that we can revert a decent chunk of
> commit
>   a0a4601765.  It might be possible to do better via smarter
> lookahead code
>   or a more sophisticated cache, but it's a bit late in the game for
> that.

This simplifies commit a0a4601765. I'd break out that simplification as
a separate commit to make it easier to understand what happened.

In patch 0003, there are quite a few static function-scoped variables,
which is not a style that I'm used to. One idea is to bundle them into
a struct representing the cache state (including enough information to
fetch the next batch), and have a single static variable that points to
that.

Also in 0003, the "next_te" variable is a bit confusing, because it's
actually the last TocEntry, until it's advanced to point to the current
one.

Other than that, looks good to me.

Regards,
Jeff Davis