On Wed, Jan 13, 2021 at 12:08 AM Stephen Frost <sfrost@snowman.net> wrote:
No, we can't 'modify the page format as we wish'- if we change away from using a C structure then we're going to be modifying quite a bit of code which otherwise doesn't need to be changed. The proposed flag doesn't actually make a different page format work, the only thing it would do would be to allow some parts of the cluster to be encrypted and other parts not be, but I don't know that that's actually a useful capability or a good reason to use one of those bits. Having it handled on a cluster level, at initdb time through pg_control, seems like it'd work just fine.
Yes, I realized that for cluster-level encryption, it would be unwise to flag a single page(Unless we want to do it at relation-level). Forgive me for not describing clearly, the 'modify the page' I said means the method you mentioned, not modifying the C structure. My original motivation is to avoid storing in an unconventional format without a description of the C structure. However, as I just said, it seems that we should not set the flag for a single page. Maybe it's enough to just add a comment description?