Re: attdisbursion

Added to TODO. This will improve VACUUM ANALYZE performance, thought I
don't think we have btree comparison functions for all data types,
though we should:

* change VACUUM ANALYZE to use btree comparison functions, not <,=,> calls

> > > Also, I have idea about using '<' '>' in vacuum:
> > > what if try to use btree BT_ORDER functions which allow
> > > to compare vals for many data types (btXXXcmp functions in
> > > nbtcompare.c).
> >
> > I see, use a btree index to tell use how selective the > or < is? An
> > interesting idea. Isn't there a significant performance problem with
> > this?
>
> Don't use btree index, but use btree functions to compare
> two values of a datatype. You call
> func_operator = oper("<",...
> "="
> ">"
> but this's not right way in common case: operators may be
> overloaded.
>
> These functions are stored in catalog.
> To get function for a datatype btree call
>
> proc = index_getprocid(rel, 1, BTORDER_PROC);
>
> Look @ nbtcompare.c:
>
> * These functions are stored in pg_amproc. For each operator class
> * defined on btrees, they compute
> *
> * compare(a, b):
> * < 0 if a < b,
> * = 0 if a == b,
> * > 0 if a > b.
>
> There are functions for INTs, FLOATs, ...
>
> ...But this is not so important thing...
>
> Vadim
>

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