Bruce Momjian <pgman@candle.pha.pa.us> writes:
> Agreed. What I am wondering is with our system where every update gets
> a new row, how would this help us? I know we try to keep an update on
> the same row as the original, but is there any significant performance
> benefit to doing that which would offset the compaction advantage?
Because Oracle uses overwrite-in-place (undoing from an UNDO log on
transaction abort), while we always write a whole new row, it would take
much larger PCTFREE wastage to get a useful benefit in PG than it does
in Oracle. That wastage translates directly into increased I/O costs,
so I'm a bit dubious that we should assume there is a win to be had here
just because Oracle offers the feature.
regards, tom lane
