On 02/18/2013 15:39, Bert wrote:
Hello,
Thanks the nice people on irc my problem is fixed.
I changed the following settings in the postgres.conf file:
default_statistics_target = 5000 -> and I analyzed the tables after
the change of course -> now I only got 2 plans anymore, in stead of 3
default_statistics_target = 5000 as a default is *way* too high. Such
high values should only be set on a per-column basis ...
cpu_tuple_cost = 0.1 -> by setting this value the seq scans were
stopped, and the better index_only scan / bitmap index scan were used
for this query.
Thank you Robe and Mabe_ for helping me with this issue!
s/Mabe_/Mage_ :-)
wkr,
Bert
On Mon, Feb 18, 2013 at 2:42 PM, Bert <bier...@gmail.com
<mailto:bier...@gmail.com>> wrote:
Hello,
yes, the tables are vacuumed every day with the following command:
vacuum analyze schema.table.
The last statistics were collected yesterday evening. I collected
statistics about the statistics, and I found the following:
table_name; starttime; runtime
"st_itemseat";"2013-02-17 23:48:42";"00:01:02"
"st_itemseat_45";"2013-02-17 23:35:15";"00:00:08"
"st_itemzone";"2013-02-17 23:35:33";"00:00:01"
st_itemseat_45 is a child-partition of st_itemseat.
They seem to be pretty much up to date I guess?
I also don't get any difference in the query plans when they are
run in the morning, or in the evening.
I have also run the query with set seq_scan to off, and then I get
the following output:
Total query runtime: 12025 ms.
20599 rows retrieved.
and the following plan: http://explain.depesz.com/s/yaJK
These are 3 different plans. And the last one is blazingly fast.
That's the one I would always want to use :-)
it's also weird that this is default plan for the biggest
partition. But the smaller the partition gets, the smaller the
partition gets.
So I don't think it has anything to do with the memory settings.
Since it already chooses this plan for the bigger partitions...
wkr,
Bert
On Mon, Feb 18, 2013 at 11:51 AM, Frank Lanitz
<fr...@frank.uvena.de <mailto:fr...@frank.uvena.de>> wrote:
Am 18.02.2013 10:43, schrieb Bert:
> Does anyone has an idea what triggers this bad plan, and how
I can fix it?
Looks a bit like wrong statistics. Are the statistiks for your
tables
correct?
Cheers,
Frank
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--
Bert Desmet
0477/305361
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Bert Desmet
0477/305361
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