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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