Re: XID formatting and SLRU refactorings (was: Add 64-bit XIDs into PostgreSQL 15)

On Mon, 6 Nov 2023 at 17:07, Alexander Korotkov <aekorotkov@gmail.com> wrote:
>
> Hi!
>
> On Wed, Jul 5, 2023 at 4:46 PM Aleksander Alekseev <aleksander@timescale.com> wrote:
> > PFE the corrected patchset v58.
>
> I'd like to revive this thread.
>
> This patchset is extracted from a larger patchset implementing 64-bit xids.  It converts page numbers in SLRUs into
64bits.  The most SLRUs save the same file naming scheme, thus their on-disk representation remains the same.  However,
thepatch 0002 converts pg_notify to actually use a new naming scheme.  Therefore pg_notify can benefit from
simplificationand getting rid of wraparound. 
>
> -#define TransactionIdToCTsPage(xid) \
> -   ((xid) / (TransactionId) COMMIT_TS_XACTS_PER_PAGE)
> +
> +/*
> + * Although we return an int64 the actual value can't currently exceeed 2**32.
> + */
> +static inline int64
> +TransactionIdToCTsPage(TransactionId xid)
> +{
> +   return xid / (int64) COMMIT_TS_XACTS_PER_PAGE;
> +}
>
> Is there any reason we transform macro into a function?  If not, I propose to leave this as a macro.  BTW, there is a
typoin a word "exceeed". 
If I remember right, the compiler will make equivalent code from
inline functions and macros, and functions has an additional benefit:
the compiler will report type mismatch if any. That was the only
reason.

Also, I looked at v58-0001 and don't quite agree with mentioning the
authors of the original 64-xid patch, from which the current patch is
derived, as just "privious input" persons.

Regards, Pavel Borisov