Manfred Koizar wrote: > On Fri, 2 Sep 2005 15:51:15 -0400 (EDT), Bruce Momjian > <pgman@candle.pha.pa.us> wrote: > > * Merge xmin/xmax/cmin/cmax back into three header fields > > And don't forget xvac, please. > > > Before subtransactions, there used to be only three fields needed to > > store these four values. > > ... five values. > > > This was possible because only the current > > transaction looks at the cmin/cmax values. > > Which is a reason to get rid of cmin/cmax in tuple headers entirely. > Once I had a patch based on 7.4 that stored cmin and cmax in > backend-local memory. It passed make check and some volume tests, but > I felt it was not ready to be applied without any spill-to-disk > mechanism. Development stalled when I tried to eliminate xvac as > well, which would have required deep cuts into VACUUM code :-(
Interesting idea, but how would you record the cmin/xmin values without requiring unlimited memory? -- Bruce Momjian | http://candle.pha.pa.us pgman@candle.pha.pa.us | (610) 359-1001 + If your life is a hard drive, | 13 Roberts Road + Christ can be your backup. | Newtown Square, Pennsylvania 19073 ---------------------------(end of broadcast)--------------------------- TIP 5: don't forget to increase your free space map settings
