Re: tid_blockno() and tid_offset() accessor functions

On Wed, Mar 11, 2026 at 2:50 PM Andres Freund <andres(at)anarazel(dot)de> wrote:
>
> Hi,
>
> On 2026-03-11 14:48:08 -0700, Masahiko Sawada wrote:
> > On Fri, Feb 27, 2026 at 10:59 AM Ayush Tiwari
> > <ayushtiwari(dot)slg01(at)gmail(dot)com> wrote:
> > >
> > > Hi hackers,
> > >
> > > As of now we don't have any built-in way to extract the block and offset components from a TID. When people need to group by page (like for bloat analysis) or filter by specific blocks, they usually end up using the `ctid::text::point` hack:
> > >
> > > SELECT (ctid::text::point)[0]::bigint AS blockno,
> > > (ctid::text::point)[1]::int AS offset
> > > FROM my_table;
> > >
> > > This works, but it's pretty clunky, relies on the text representation, and isn't great if you're trying to parse TIDs outside of SQL.
> > >
> > > The attached patch adds two simple accessor functions:
> > > - `tid_blockno(tid) -> bigint`
> > > - `tid_offset(tid) -> integer`
> >
> > How about adding the subscripting support for tid data type? For
> > example, ctid[0] returns bigint and ctid[1] returns int.
>
> That just seems less readable and harder to find to me. I think it'd also
> make the amount of required code noticeably larger?

Yeah, using the dedicated functions would be more intuitive than using
magic numbers 1 and 2, and require less code.

Regards,

--
Masahiko Sawada
Amazon Web Services: https://aws.amazon.com