Hi,
I have a question about a query that starts out fine and over time slows to a
halt - but only on a webhosted site. Locally it does fine.
The query is a singleton select (no joins), hitting a table with about 5,000
records in it. Over time the query slows to a crawl and I have to dump and
rebuild/repopulate to restore efficiency. Vacuum does nothing but a dump and
reload fixes the problem and the query runs lightning fast again -- for a
period of a week or so. As stated this only happens on the webhosted site
(bluehost.com). Locally I have the same table with 118,000 records in it and it
runs very fast. (Related: even a "SELECT COUNT(*) on the the target table takes
forever when the lethargy has set in).
The only thing that might be a factor that I can see is that my ORDER BY uses
an unindexed date - however, we have a sister site on the same webhost (diff
server) and it does not experience slowdowns.
With everything working properly (table rebuilt just yesterday) explain analyze
produces this on the webhost:
Sort (cost=121547.89..121558.43 rows=4214 width=4620) (actual
time=386.172..386.224 rows=89 loops=1)
Sort Key: visit_date
-> Seq Scan on client_service_note (cost=0.00..100334.19 rows=4214
width=4620) (actual time=0.019..385.917 rows=89 loops=1)
Filter: (client_id = 385)
Total runtime: 386.335 ms
And locally:
Sort (cost=535.82..536.04 rows=88 width=696) (actual time=2.140..2.156
rows=88 loops=1)
Sort Key: visit_date
Sort Method: quicksort Memory: 65kB
-> Seq Scan on client_service_note (cost=0.00..532.98 rows=88 width=696)
(actual time=0.014..1.988 rows=88 loops=1)
Filter: (client_id = 385)
Total runtime: 2.295 ms
My query is terse:
SELECT * FROM client_service_note WHERE client_id = 385 ORDER BY visit_date
DESC;
Locally I'm running 8.4.2, the webhost is 8.1.18
Anyone have any thoughts on what I'm not seeing??
thanks,
Tom
--
Thomas Good, Senior Database Administrator
Residential Services, Behavioral Health Services
Bayley Seton Campus, SVCMCNY
75 Vanderbilt Avenue, Room 5-47
Staten Island, NY 10304
718.818.5528
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