On Mar 17, 2007, at 10:33 PM, Luke Lonergan wrote:
Wow, nice!
Can you tell us:
- how big is the table
- cardinality of the column
- how big is the index in each case
- how much memory on the machine
- query and explain analyze
All I changed, was the 400k to 150k
512MB of ram, as I said earlier. And it is running 64bit kernel,
32bit user-land on linux 2.6.20
query and explain is going to run for a while, so I'll leave it - as
it is going to be the same on other machines (much faster ones).
postgres=# select pg_size_pretty( pg_relation_size
( 'narrowtable_index' ) );
pg_size_pretty
----------------
321 MB
(1 row)
postgres=# select pg_size_pretty( pg_relation_size
( 'narrowtable2_clustered_index' ) );
pg_size_pretty
----------------
3960 kB
(1 row)
(so there's quite a difference).
Judging from noises coming out of machine, there was pretty loads of
I/O activity. and funny enough, one CPU was stucked on 'wait' up to
80% most of the time.
the 'cardinality', as I guess, uniqueness is the same as intended in
original test. Like I said, only table size was changed.
select count(distinct key) from narrowtable; and select count(*) from
narrowtable; are the same - 15000000
hth.
--
Grzegorz Jaskiewicz
C/C++ freelance for hire
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