building gist index on int[] field is terrible slow. Is it bug?

Hello

I tested contrib package intarray and gist support from this package.
I was surpirised. Index building needed lot of time.

10K fields .. 106sec
20K f ..265 sec
30Kf .. 450 sec
50Kf .. 1283sec

building gin index for 50K fields needed 0.5sec

Regards
Pavel Stehule

sample of data:
pavel=# select * from test limit 10;
a
-----------------------
{4209,4207,4197,2066}
{4832,3004}
{4629}
{3243}
{4816}
{3726}
{4834}
{1459,3160,3984}
{4569}
{4164,1307,962,4482}
(10 rows)

pavel=# select version();
version
-------------------------------------------------------------------------------------------------------
PostgreSQL 8.3devel on i686-pc-linux-gnu, compiled by GCC gcc (GCC)
4.1.2 20070502 (Red Hat 4.1.2-12)
(1 row)

Time: 442,034 ms

pavel=# show maintenance_work_mem ;
maintenance_work_mem
----------------------
16MB
(1 row)

pavel=# set maintenance_work_mem to '300MB';
SET
Time: 0,230 ms
pavel=#
pavel=# CREATE index fooidx on test using gist(a gist__int_ops);
CREATE INDEX
Time: 1269276,866 ms