Re: Brain dump: btree collapsing

Tom Lane kirjutas R, 14.02.2003 kell 01:13:
> Hannu Krosing <hannu@tm.ee> writes:
> > But if we would allow the scans to find the same keys twice without ill
> > effects (as was suggested earlier, for using btrees to index arrays),
>
> How is returning the same data twice not an "ill effect"?

>From earlier discussions I understood that there had been some work done
on using btrees for indexing arrays by storing each separate element in
a löeaf node. Surely that work must deal with not returning the same
tuple twice.

> > then we could possibly 1) copy the key to the right 2) wait for all
> > right-to-left scans that have fallen between old and new values to pass
> > and only then 3) delete the "old left" key.
>
> How will you wait for scans that you know nothing of to go past?
> Especially when they are going to be blocked by your own write lock
> on the left page?

could we just not lock (for more than just to ensure atomic writes) the
page but instead increment a "page version" on each write to detect
changes?

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Hannu