Re: [PATCH] Add min() and max() aggregate functions for xid8

[Fujii Masao]

On 2022/02/03 16:45, Ken Kato wrote:

Hi hackers,

Unlike xid, xid8 increases monotonically and cannot be reused.
This trait makes it possible to support min() and max() aggregate functions for 
xid8.
I thought they would be useful for monitoring.

So I made a patch for this.

Thanks for the patch! +1 with this feature.

+       PG_RETURN_FULLTRANSACTIONID((U64FromFullTransactionId(fxid1) > 
U64FromFullTransactionId(fxid2)) ? fxid1 : fxid2);

Shouldn't we use FullTransactionIdFollows() to compare those two fxid values 
here, instead?

+       PG_RETURN_FULLTRANSACTIONID((U64FromFullTransactionId(fxid1) < 
U64FromFullTransactionId(fxid2)) ? fxid1 : fxid2);

Shouldn't we use FullTransactionIdPrecedes() to compare those two fxid values 
here, instead?

Could you add the regression tests for those min() and max() functions for xid8?

Regards,

--
Fujii Masao
Advanced Computing Technology Center
Research and Development Headquarters
NTT DATA CORPORATION