Re: assorted problems with intarray and other GiST contribs.

On Sun, Jun 26, 2005 at 06:48:42PM +0200, PFC wrote:
>
> SELECT int_array_aggregate(id) FROM (SELECT id FROM shop.products LIMIT X)
> as foo;
>
> This one works fine if X <= 512 and crashes postgres if X > 512.
> ie. if the aggregate accumulates more than 512 values it crashes.

I don't get a crash in 8.0.3. I do see some items regarding
contrib/intagg in the 8.0.3 and 8.0.2 Release Notes, so maybe this
problem has already been fixed. Do you have an 8.0.3 installation
you could test?

> SELECT int_array_aggregate(product_id),
> int_array_aggregate(category_id)
> FROM (SELECT * FROM shop.products_to_categories LIMIT N) as foo;
>
> OK if N <= 8, crashes if N > 9

Works for me in 8.0.3.

> int[] & int[] - returns intersection of arrays
>
> This is a useful function but it is very slow.
> Computing the intersection of two int[] of length 100 takes about 40
> ms.

How are you timing the operation? What kind of hardware are you
using? I have a 500MHz Pentium III that computes the intersection
of two 100-element arrays in about 0.5ms; in 40ms it can do arrays
of about 1100 elements. I'm measuring this with a PL/pgSQL function
that does the following:

t1 := timeofday();
c := a & b;
t2 := timeofday();
dt := t2 - t1;

> It would be nice to have functions to :
> - know the length of a ltree (ie. number of elements)

Does nlevel() not do what you want?

> - access it like an array (ie. get element N).

Does subpath() or subltree() not do what you want?

> Also a function returning the comon prefix between two ltrees would
> be really useful.

Does lca() not do what you want?

--
Michael Fuhr
http://www.fuhr.org/~mfuhr/