am 22.08.2005, um 22:13:49 +0200 mailte Ben-Nes Yonatan folgendes:
I think that I was misunderstood, Ill make an example:
Okay:
Lets say that im making the following query for the first time on the
"motorcycles" table which got an index on the "manufacturer" field:
EXPLAIN ANALYZE SELECT manufacturer FROM motorcycles WHERE
manufacturer='suzuki';
.. Total runtime: 3139.587 ms
neither the DB nor the OS has the the table and index in the cache.
Now im doing the same query again and i get a much faster result (cause of
the "caching"): Total runtime: 332.53 ms
OS and DN has now the table and index in the cache.
After both of those queries I drop the index and query the table again with
the exact same query as before and now I receive: Total runtime: 216834.871
ms
Without index -> DB make a seq-scan. Very slow, of cource.
And for my last check I run the exact same query again (without creating
the INDEX back again) and I get quite similar result to my third query:
Total runtime: 209218.01 ms
Never mind. The table is too big for the cache.
My problem is that (maybe I just dont understand something basic here...)
the last 2 (also the second query but I dont care about that) queries were
using the "cache" that was created after the first query (which had an
INDEX) so none of them actually showed me what will happen if a client will
do such a search (without an INDEX) for the first time.
I want to delete that "caching" after I do the first 2 queries so my next
queries will show me "real life results".
No problem: demount all RAM and send this to me ;-)
Regards, Andreas
heheheh sure to which address should I send it? :P
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