Re: Analysis of ganged WAL writes

"Zeugswetter Andreas SB SD" <ZeugswetterA@spardat.at> writes:
> Can the magic be, that kaio directly writes from user space memory to the 
> disk ?

This makes more assumptions about the disk drive's behavior than I think
are justified...

> Since in your case all transactions A-E want the same buffer written,
> the memory (not it's content) will also be the same.

But no, it won't: the successive writes will ask to write different
snapshots of the same buffer.

> The problem I can see offhand is how the kaio system can tell which
> transaction can be safely notified of the write,

Yup, exactly.  Whose snapshot made it down to (stable) disk storage?
        regards, tom lane