"Kevin Grittner" <Kevin.Grittner@wicourts.gov> writes:
> Greg Stark <gsstark@mit.edu> wrote:
>> That doesn't work because when you split an index page any
>> sequential scan in progress will either see the same tuples twice
>> or will miss some tuples depending on where the new page is
>> allocated. Vacuum has a clever trick for solving this but it
>> doesn't work for arbitrarily many concurrent scans.
> It sounds like you're asserting that Index Scan nodes are inherently
> unreliable, so I must be misunderstanding you.
We handle splits in a manner that insures that concurrent index-order
scans remain consistent. I'm not sure that it's possible to scale that
to ensure that both index-order and physical-order scans would remain
consistent. It might be soluble but it's certainly something to worry
about.
regards, tom lane