Re: Unneccessary cmax in heap tuple ?

> > Why is there cmax in tuple ? cxxx is used to determine
> > if tuple was inserted/deleted by current command or
> > past command. Because one command can't both insert
> > and delete the same tuple, only something like "cupd"
> > might be needed and flag which tells you whether cupd
> > is time of insert or delete. This saves 4byte from
> > header ..
> 
> If a tuple was inserted and updated in current transaction,
> how could we judge if the tuple was valid for a given
> ScanCommandId  ?
> However there could be other improvements.

Ahh I did not know that there is need to test tuple for
validity for some past cid. I thought that we only need
to know whether tuple has been updated by current cid
to ensure that it will not be scanned again in the same
cid... Where am I wrong ?
devik