[postgis-users] ST_SPHEROID_LENGTH SLOW

[David Vaz]

Actually the first time this happened was with 8.3+1.3.3, at that time
debian still didn't have the postgis package for postgres 8.3 so I
compiled postgis myself. Having that slow performance with that query I
figured I had done something wrong with the compilation, so I stayed
with 8.2+1.3.2, this week I tried again, given that debian testing
already had postgis packages, but the speed was the same.

Paul Ramsey wrote:
> That's deeply odd, and worth investigating. Can you try 8.3+1.3.3, so
> we can eliminate the PostGIS version as a variable first? Then I'll
> see if I can duplicate the result on my system.
>
> P.
>
> On Sat, Sep 27, 2008 at 12:59 PM, David Vaz <davidvaz at dcc.fc.up.pt> wrote:
>   
>> Hi,
>>
>> I am a debian user, several months ago debian testing introduced
>> postgresql-8.3, and later postgis 1.3 for postgresql-8.3. The problem I
>> am facing is that length_spheroid is much slower in postgres-8.3 from
>> under 1s to about 60s (See Bellow). I have google-it without any luck.
>> Does anyone have any idea on why this happens?
>>
>> Both databases are equal, tested in same machine, with different
>> installations to avoid software versions conflicts.
>>
>> FIRST:
>> postgresql-8.2 (version 8.2.7-2+b1) with postgis (version 1.3.2-1)
>>
>> EXPLAIN ANALYSE select length_spheroid(geom,'SPHEROID["WGS
>> 84",6378137,298.257223563]') FROM test order by id limit 100;
>>
>> QUERY
>> PLAN
>> -------------------------------------------------------------------------------------------------------------------------------------------------------
>>  Limit  (cost=0.00..17.44 rows=100 width=26054) (actual
>> time=1.852..588.394 rows=100 loops=1)
>>   ->  Index Scan using test_pkey on test  (cost=0.00..2268.52
>> rows=13010 width=26054) (actual time=1.850..588.298 rows=100 loops=1)
>>  Total runtime: 588.495 ms
>> (3 rows)
>>
>> SECOND:
>> postgresql-8.3 (version 8.3.3-1) with postgis (version 1.3.3-3)
>>
>> EXPLAIN ANALYSE select length_spheroid(geom,'SPHEROID["WGS
>> 84",6378137,298.257223563]') FROM test order by id limit 100;
>>
>> QUERY
>> PLAN
>>
>> ------------------------------------------------------------------------------------------------------------------------------------------------------------
>>  Limit  (cost=0.00..8.74 rows=100 width=104429) (actual
>> time=182.734..59741.720 rows=100 loops=1)
>>   ->  Index Scan using test_pkey on test  (cost=0.00..1137.11
>> rows=13010 width=104429) (actual time=182.732..59741.572 rows=100 loops=1)
>>  Total runtime: 59741.897 ms
>> (3 rows)
>>
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>>
>>     
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