Re: Upper limit arguments of pg_logical_slot_xxx_changes functions accept invalid values

Thank you for comment!

On Fri, Jul 27, 2018 at 7:27 AM, Michael Paquier <michael(at)paquier(dot)xyz> wrote:
> On Thu, Jul 12, 2018 at 09:58:16AM +0900, Masahiko Sawada wrote:
>> If upto_lsn is non-NULL, decoding will include only those
>> transactions which commit prior to the specified LSN. If upto_nchanges
>> is non-NULL, decoding will stop when the number of rows produced by
>> decoding exceeds the specified value.
>
> It is also possible to interpret a negative value as an equivalent to
> infinite, no? That's how I read the documentation quote you are adding
> here.

Given the meaning of upto_nchanges I would expect that the "non-NULL"
is a positive value but it's possible to interpret as you mentioned.
Maybe this patch should fix only the code setting InvalidXLogRecPtr to
upto_nchanges.

Regards,

--
Masahiko Sawada
NIPPON TELEGRAPH AND TELEPHONE CORPORATION
NTT Open Source Software Center