On 2025-Apr-02, Peter Geoghegan wrote: > On Wed, Apr 2, 2025 at 12:31 PM Álvaro Herrera <alvhe...@alvh.no-ip.org> > wrote: > > The mentioned commit (09cb5c0e7d6f) shows that we do partial memcpys, e.g. > > > > + memcpy(&so->markPos, &so->currPos, > > + offsetof(BTScanPosData, items[1]) + > > + so->currPos.lastItem * sizeof(BTScanPosItem)); > > > > That would obviously not work if this field weren't last. We still do > > that, don't we? See btrestrpos(). > > Yes, we do -- but it's rare. It only happens in the case where we > restore a mark after leaving the page where the mark was taken. In > practice, merge joins tend to hardly ever do that (I know this because > it makes testing annoyingly difficult). In other words, the > optimization added by commit 08ae5edc5c seems to be very effective in > practice.
I'm just saying that this is the reason to have the field be last in the struct. -- Álvaro Herrera Breisgau, Deutschland — https://www.EnterpriseDB.com/ "La rebeldía es la virtud original del hombre" (Arthur Schopenhauer)
