possible problem with indexes postgresql-6.5.2

i have a large table that gets added to frequently (2-3 times per hour, 50K
or more records each time).

this table has a single index, unique, a char(20) field.

every now and then, the index seems to grow abnormally, although it appears
to function fine.

here is an ls -l, before:

-rw------- 1 pgsql wheel 1073741824 Nov 6 23:34 gt
-rw------- 1 pgsql wheel 1073741824 Nov 6 23:36 gt.1
-rw------- 1 pgsql wheel 1073741824 Nov 6 23:37 gt.2
-rw------- 1 pgsql wheel 796180480 Nov 7 17:11 gt.3
-rw------- 1 pgsql wheel 0 Oct 28 00:15 gt.4
-rw------- 1 pgsql wheel 1073111040 Nov 7 17:11 gt_callid_key

another round of inserts hit, and then i did:
"drop index gt_callid_key;"
"vacuum verbose;"
"create unique index gt_callid_key on gt (callid);"

-rw------- 1 pgsql wheel 1073741824 Nov 7 17:22 gt
-rw------- 1 pgsql wheel 1073741824 Nov 7 17:24 gt.1
-rw------- 1 pgsql wheel 1073741824 Nov 6 23:37 gt.2
-rw------- 1 pgsql wheel 797941760 Nov 7 18:12 gt.3
-rw------- 1 pgsql wheel 0 Oct 28 00:15 gt.4
-rw------- 1 pgsql wheel 359399424 Nov 7 18:12 gt_callid_key

from time to time, i have seen gt_callid_key grow to in excess of 50% the size
of the main table.

any ideas?

this is postgres-6.5.2 (patched from 6.5.1) on intel hardware under FreeBSD.

--
[ Jim Mercer jim(at)reptiles(dot)org +1 416 506-0654 ]
[ Reptilian Research -- Longer Life through Colder Blood ]
[ Don't be fooled by cheap Finnish imitations; BSD is the One True Code. ]