Re: Is this a problem in GenericXLogFinish()?

On Wed, Apr 10, 2024 at 1:27 PM Michael Paquier <michael(at)paquier(dot)xyz> wrote:
>
> On Tue, Apr 09, 2024 at 10:25:36AM +0000, Hayato Kuroda (Fujitsu) wrote:
> >> On Fri, Apr 05, 2024 at 06:22:58AM +0000, Hayato Kuroda (Fujitsu) wrote:
> >> I'm slightly annoyed by the fact that there is no check on
> >> is_prim_bucket_same_wrt for buffer 1 in the BLK_NEEDS_REDO case to
> >> show the symmetry between the insert and replay paths. Shouldn't
> >> there be at least an assert for that in the branch when there are no
> >> tuples (imagine an else to cover xldata->ntups == 0)? I mean between
> >> just before updating the hash page's opaque area when
> >> is_prev_bucket_same_wrt.
> >
> > Indeed, added an Assert() in else part. Was it same as your expectation?
>
> Yep, close enough. Thanks to the insert path we know that there will
> be no tuples if (is_prim_bucket_same_wrt || is_prev_bucket_same_wrt),
> and the replay path where the assertion is added.
>

It is fine to have an assertion for this path.

+ else
+ {
+ /*
+ * See _hash_freeovflpage() which has a similar assertion when
+ * there are no tuples.
+ */
+ Assert(xldata->is_prim_bucket_same_wrt ||
+ xldata->is_prev_bucket_same_wrt);

I can understand this comment as I am aware of this code but not sure
it would be equally easy for the people first time looking at this
code. One may try to find the equivalent assertion in
_hash_freeovflpage(). The alternative could be: "Ensure that the
required flags are set when there are no tuples. See
_hash_freeovflpage().". I am also fine if you prefer to go with your
proposed comment.

Otherwise, the patch looks good to me.

--
With Regards,
Amit Kapila.