Re: TOAST on indices

At 20:42 4/07/00 +0200, Jan Wieck wrote:
>
> So an index (built out of the values in the
> main tuple after toasting) will also contain the plain
> values. Thus, index scans will not require toast fetches in
> turn. Except the indexed attribute had at some point a huge
> value.

So that, for toasted attrs, the indexes will be no use for sorting. I agree
that in the majority of cases this is not a problem, but if the entire
tuple gets toasted because it is too large it becomes a problem.

I agree that this is only a problem if indexes are used in sorting, and may
not be a problem if one builds an index on 'substr(toastable-field,1,20)',
but I think you are suggesting not supporting functional indexes,
below...but maybe I've missed the point.

> The current TOAST implementation hooks into the heap access
> methods only. Automagically covering the index issues due to
> the 2K approach. Fact is, that if more toast entries can get
> produced during index inserts, we need to take care for them
> during vacuum (the only place where index items get removed).
> Alot of work just to support huge functional indices - IMHO
> not worth the efford right now. Let's better get some
> experience with the entire thing before going too far.
>

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