Re: Cursor fetch performance issue

> On Tue, 2012-01-24 at 21:47 +0100, Pavel Stehule wrote:
>> Hello
>>
>> 2012/1/24 Tony Capobianco<tcapobianco(at)prospectiv(dot)com>:
>>> We are migrating our Oracle warehouse to Postgres 9.
>>>
>>> This function responds well:
>>>
>>> pg=# select public.getMemberAdminPrevious_sp2(247815829, 1,'test(dot)email(at)hotmail(dot)com', 'email', 'test');
>>> getmemberadminprevious_sp2
>>> ----------------------------
>>> <unnamed portal 1>
>>> (1 row)
>>>
>>> Time: 7.549 ms
>>>
>>> However, when testing, this fetch takes upwards of 38 minutes:
>>>
>>> BEGIN;
>>> select public.getMemberAdminPrevious_sp2(247815829, 1,'test(dot)email(at)hotmail(dot)com', 'email', 'test');
>>> FETCH ALL IN "<unnamed portal 2>";
>>>
>>> How can I diagnose any performance issues with the fetch in the cursor?
>>>
>>
>> Cursors are optimized to returns small subset of result - if you plan
>> to read complete result, then set
>>
>> set cursor_tuple_fraction to 1.0;
>>
>> this is session config value, you can set it before selected cursors queries
>>
>> Regards
>>
>> Pavel Stehule
>>
>>> Thanks.
>>> Tony
>>>
>>>
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>>
>
>
>

On 1/24/2012 2:57 PM, Tony Capobianco wrote:
> Running just the sql of the function returns only 10 rows:
>
> pg=# SELECT m.memberid, m.websiteid, m.emailaddress,
> pg-# m.firstname, m.lastname, m.regcomplete, m.emailok
> pg-# FROM members m
> pg-# WHERE m.emailaddress LIKE 'test(dot)email(at)hotmail(dot)com'
> pg-# AND m.changedate_id< 5868 ORDER BY m.emailaddress,
m.websiteid;
> memberid | websiteid | emailaddress | firstname |
lastname | regcomplete | emailok
>
-----------+-----------+------------------------+-----------+----------+-------------+---------
> 247815829 | 1 | test(dot)email(at)hotmail(dot)com | email | test
| 1 | 1
> 300960335 | 62 | test(dot)email(at)hotmail(dot)com | |
| 1 | 1
> 300959937 | 625 | test(dot)email(at)hotmail(dot)com | |
| 1 | 1
> 260152830 | 1453 | test(dot)email(at)hotmail(dot)com | |
| 1 | 1
> 300960163 | 1737 | test(dot)email(at)hotmail(dot)com | email | test
| 1 | 1
> 300960259 | 1824 | test(dot)email(at)hotmail(dot)com | email | test
| 1 | 1
> 300959742 | 1928 | test(dot)email(at)hotmail(dot)com | email | test
| 1 | 1
> 368122699 | 2457 | test(dot)email(at)hotmail(dot)com | email | test
| 1 | 1
> 403218613 | 2464 | test(dot)email(at)hotmail(dot)com | email | test
| 1 | 0
> 378951994 | 2656 | test(dot)email(at)hotmail(dot)com | |
| 1 | 1
> (10 rows)
>
> Time: 132.626 ms
>
> So, it would seem that's a small enough number of rows.
Unfortunately, issuing:
>
> set cursor_tuple_fraction to 1.0;
>
> Did not have an effect on performance. Is it common to modify this
> cursor_tuple_fraction parameter each time we execute the function?
>
>

So, is getMemberAdminPrevious_sp2() preparing a statement with wildcards?

SELECT m.memberid, m.websiteid, m.emailaddress,
m.firstname, m.lastname, m.regcomplete, m.emailok
FROM members m
WHERE m.emailaddress LIKE $1
AND m.changedate_id < $2
ORDER BY m.emailaddress, m.websiteid;

Or is it creating the string and executing it:

sql = 'SELECT m.memberid, m.websiteid, m.emailaddress, '
|| ' m.firstname, m.lastname, m.regcomplete, m.emailok '
|| ' FROM members m
|| ' WHERE m.emailaddress LIKE ' || arg1
|| ' AND m.changedate_id < ' || arg2
|| ' ORDER BY m.emailaddress, m.websiteid ';
execute(sql);

Maybe its the planner doesnt plan so well with $1 arguments vs actual
arguments thing.

-Andy