Re: foreign key locks

Andres Freund <andres@2ndquadrant.com> writes:
> On 2013-01-18 15:37:47 -0500, Tom Lane wrote:
>> I doubt it ever came up before.  What use is logging only the content of
>> a buffer page?  Surely you'd need to know, for example, which relation
>> and page number it is from.

> It only got to be a length of 0 because the the data got removed due to
> a logged full page write. And the backup block contains the data about
> which blocks it is logging in itself.

And if the full-page-image case *hadn't* been invoked, what then?  I
still don't see a very good argument for xlog records with no fixed
data.

> I wonder if the check shouldn't just check write_len instead, directly
> below the loop that ads backup blocks.

We're not changing this unless you can convince me that the read-side
error check mentioned in the comment is useless.
        regards, tom lane