Re: [HACKERS] Setting pd_lower in GIN metapage

Amit Langote <Langote_Amit_f8@lab.ntt.co.jp> writes:
> On 2017/08/22 9:39, Michael Paquier wrote:
>> On Tue, Jun 27, 2017 at 4:56 PM, Amit Langote
>> <Langote_Amit_f8@lab.ntt.co.jp> wrote:
>>> I updated brin_mask() and spg_mask() in the attached updated patches so
>>> that they consider meta pages as containing unused space.

I looked briefly at these patches.  I'm not sure that it's safe for the
mask functions to assume that meta pages always have valid pd_lower.
What happens when replaying log data concerning an old index that doesn't
have that field filled?
        regards, tom lane