Ühel kenal päeval, K, 2007-03-14 kell 10:22, kirjutas Heikki
Linnakangas:
> Tom Lane wrote:
> > At this point I'm feeling unconvinced that we want it at all. It's
> > sounding like a large increase in complexity (both implementation-wise
> > and in terms of API ugliness) for a fairly narrow use-case --- just how
> > much territory is going to be left for this between HOT and bitmap indexes?
>
> I'm in a awkward situation right now. I've done my best to describe the
> use cases for clustered indexes.
...
> Just to recap the general idea: reduce index size taking advantage of
> clustering in the heap.
>
> Clustered indexes have roughly the same performance effect and use cases
> as clustered indexes on MS SQL Server, and Index-Organized-Tables on
> Oracle, but the way I've implemented them is significantly different. On
> other DBMSs, the index and heap are combined to a single b-tree
> structure. The way I've implemented them is less invasive, there's no
> changes to the heap for example, and it doesn't require moving live tuples.
Do you keep visibility info in the index ?
How does this info get updated when visibility data changes in the
heap ?
If there is no visibility data in index, then I can't see, how it gets
the same performance effect as Index-Organized-Tables, as lot of random
heap access is still needed.
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