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From: Andres Freund <[email protected]>
To: Masahiko Sawada <[email protected]>
Cc: Ayush Tiwari <[email protected]>
Cc: [email protected]
Subject: Re: tid_blockno() and tid_offset() accessor functions
Date: Wed, 11 Mar 2026 17:50:32 -0400
Message-ID: <fe2ay3acydk6sd3iwkvol7t3kgswzfsuaz2vdgqornx4hg7ji2@dpwilwuzq7a2> (raw)
In-Reply-To: <CAD21AoBdgM+4X=Wg0T==C9ahenm2nUb=q5AxxeEb_JVoKOzbgw@mail.gmail.com>
References: <CAJTYsWUzok2+mvSYkbVUwq_SWWg-GdHqCuYumN82AU97SjwjCA@mail.gmail.com>
	<CAD21AoBdgM+4X=Wg0T==C9ahenm2nUb=q5AxxeEb_JVoKOzbgw@mail.gmail.com>

Hi,

On 2026-03-11 14:48:08 -0700, Masahiko Sawada wrote:
> On Fri, Feb 27, 2026 at 10:59 AM Ayush Tiwari
> <[email protected]> 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?

Greetings,

Andres

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