Re: Single Index Tuple Chain (SITC) method

Ühel kenal päeval, N, 2006-06-29 kell 12:35, kirjutas Tom Lane:
> Martijn van Oosterhout <kleptog(at)svana(dot)org> writes:
> >> Tom - what do you think of the other related idea, that of reusing dead
> >> index entries ?
>
> Possibly workable for btree now that we do page-at-a-time index scans;
> however I'm pretty hesitant to build any large infrastructure atop that
> change until we've got more performance results. We might yet end up
> reverting it.
>
> Another issue is that this would replace a simple hint-bit setting with
> an index change that requires a WAL entry. There'll be more WAL traffic
> altogether from backends retail-deleting index tuples than there would
> be from VACUUM cleaning the whole page at once --- and it won't cut the
> I/O demand from VACUUM any, either, since VACUUM still has to scan the
> index. AFAICS this wouldn't make VACUUM either cheaper or less
> necessary, so I'm not sure I see the point.

How can it generate more traffic ?

When you replace a dead index entry with a live one, you just reuse
space - you would have to WAL log the index in both cases (adding a new
entry or replacing dead entry)

Espacially in the case, where you replace an index entryu with the same
value.

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