Tom Lane wrote:
>
> Oleg Bartunov <oleg@sai.msu.su> writes:
> > We have a problem with
> > handling NULL values in GiST. Any thought how NULL values
> > are handle in Rtree.
>
> AFAIR, none of the index access methods except btree handle NULLs at
> all --- they just ignore NULL values and don't store them in the index.
> Feel free to improve on that ;-). The physical representation of index
> tuples can handle NULLs, the problem is teaching the index logic where
> they should go in the index.
>
> regards, tom lane
and I can't see why btree stores them (as it seems to do judging by the
index file size) - at least it does not use it for searching for "IS
NULL"
--8<--------8<--------8<--------8<--------8<--------8<--------8<--------8<------
hannu=# explain select * from nulltest where i is null;
NOTICE: QUERY PLAN:
Seq Scan on nulltest (cost=0.00..293.80 rows=5461 width=8)
EXPLAIN
hannu=# explain select * from nulltest where i =1;
NOTICE: QUERY PLAN:
Index Scan using nulltest_i_ndx on nulltest (cost=0.00..96.95 rows=164
width=8)
--8<--------8<--------8<--------8<--------8<--------8<--------8<--------8<------
nulltest is a 16k record table with numbers 1 to 16384 in field i
If it just ignored them we would have a nice way to fake partial indexes
-
just define a function that returns field value or null and then index
on that ;)
-----------
Hannu
