public inbox for [email protected]  

help / color / mirror / Atom feed

From: Alvaro Herrera <[email protected]>
To: Tomas Vondra <[email protected]>
Cc: Matthias van de Meent <[email protected]>
Cc: Justin Pryzby <[email protected]>
Cc: Andres Freund <[email protected]>
Cc: Greg Stark <[email protected]>
Cc: Zhihong Yu <[email protected]>
Cc: PostgreSQL Hackers <[email protected]>
Subject: Re: PATCH: Using BRIN indexes for sorted output
Date: Fri, 24 Feb 2023 16:14:16 +0100
Message-ID: <[email protected]> (raw)
In-Reply-To: <[email protected]>

On 2023-Feb-24, Tomas Vondra wrote:

> I guess the easiest fix would be to do the arithmetic in 64 bits. That'd
> eliminate the overflow.

Yeah, that might be easy to set up.  We then don't have to worry about
it until BlockNumber is enlarged to 64 bits ... but by that time surely
we can just grow it again to a 128 bit loop variable.

> Alternatively, we could do something like
> 
>   prevHeapBlk = 0;
>   for (heapBlk = 0; (heapBlk < nblocks) && (prevHeapBlk <= heapBlk);
>        heapBlk += pagesPerRange)
>   {
>     ...
>     prevHeapBlk = heapBlk;
>   }

I think a formulation of this kind has the benefit that it works after
BlockNumber is enlarged to 64 bits, and doesn't have to be changed ever
again (assuming it is correct).

... if pagesPerRange is not a whole divisor of MaxBlockNumber, I think
this will neglect the last range in the table.

-- 
Álvaro Herrera        Breisgau, Deutschland  —  https://www.EnterpriseDB.com/

view thread (3+ messages)

reply

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Reply to all the recipients using the --to and --cc options:
  reply via email

  To: [email protected]
  Cc: [email protected], [email protected], [email protected], [email protected], [email protected], [email protected], [email protected], [email protected]
  Subject: Re: PATCH: Using BRIN indexes for sorted output
  In-Reply-To: <[email protected]>

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

This inbox is served by agora; see mirroring instructions
for how to clone and mirror all data and code used for this inbox