Re: Make relfile tombstone files conditional on WAL level

On Mon, Jan 31, 2022 at 9:37 AM Dilip Kumar <dilipbalaut(at)gmail(dot)com> wrote:
> I agree that we are using 8 bytes unsigned int multiple places in code
> as uint64. But I don't see it as an exposed data type and not used as
> part of any exposed function. But we will have to use the relfilenode
> in the exposed c function e.g.
> binary_upgrade_set_next_heap_relfilenode().

Oh, I thought we were talking about the C data type uint8 i.e. an
8-bit unsigned integer. Which in retrospect was a dumb thought because
you said you wanted to store the relfilenode AND the fork number
there, which only make sense if you were talking about SQL data types
rather than C data types. It is confusing that we have an SQL data
type called int8 and a C data type called int8 and they're not the
same.

But if you're talking about SQL data types, why? pg_class only stores
the relfilenode and not the fork number currently, and I don't see why
that would change. I think that the data type for the relfilenode
column would change to a 64-bit signed integer (i.e. bigint or int8)
that only ever uses the low-order 56 bits, and then when you need to
store a relfilenode and a fork number in the same 8-byte quantity
you'd do that using either a struct with bit fields or by something
like combined = ((uint64) signed_representation_of_relfilenode) |
(((int) forknumber) << 56);

--
Robert Haas
EDB: http://www.enterprisedb.com