Imprecision calculation value_avg in trends_uint? (Zabbix-2.0.5 + Postgresql-9.0.1)

[roman-sh]

Hello,

Why is a large range of inaccuracies in trends_uint?
Sorry for my bad English.

Experience 27 Jun 11:00
1) Time from 22 Jun 2013 00:00 to 23 Jun 2013 00:00

select AVG(value) AS value_avg from history_uint where itemid='23328' and clock>='1371844800' and clock<='1371931200';
       value_avg       
-----------------------
 1438.8833333333333333
(1 row)

select AVG(value_avg) AS avg_value_avg from trends_uint where itemid='23328' and clock>='1371844800' and clock<='1371931200';
     avg_value_avg     
-----------------------
 1426.8400000000000000
(1 row)

Inaccuracy: -<1% trends 24 hours

select AVG(value) AS value_avg, COUNT(value) AS count from history_uint where itemid='23329' and clock>='1371844800' and clock<='1371931200';
      value_avg      | count 
---------------------+-------
 63.1777777777777778 |  1440
(1 row)

select AVG(value_avg) AS avg_value_avg, COUNT(value_avg) AS count from trends_uint where itemid='23329' and clock>='1371844800' and clock<='1371931200';
    avg_value_avg    | count 
---------------------+-------
 53.4800000000000000 |    25
(1 row)

Inaccuracy: -15,9% trends 24 hours !?

2) Time from 21 Jun 2013 23:00 to 22 Jun 2013 00:00

select AVG(value) AS value_avg, COUNT(value) AS count from history_uint where itemid='23328' and clock>='1371841200' and clock<='1371844800';
       value_avg       | count 
-----------------------+-------
 1421.0666666666666667 |    60
(1 row)

select AVG(value_avg) AS avg_value_avg from trends_uint where itemid='23328' and clock>='1371841200' and clock<='1371844800';
     avg_value_avg     
-----------------------
 1451.0000000000000000
(1 row)

Inaccuracy: +2,1% trends 1 hour

select AVG(value) AS value_avg, COUNT(value) AS count from history_uint where itemid='23329' and clock>='1371841200' and clock<='1371844800';
      value_avg      | count 
---------------------+-------
 63.2000000000000000 |    60
(1 row)


select AVG(value_avg) AS avg_value_avg from trends_uint where itemid='23329' and clock>='1371841200' and clock<='1371844800';
    avg_value_avg    
---------------------
 57.0000000000000000
(1 row)

select num, value_avg, clock from trends_uint where itemid='23329' and clock>='1371841200' and clock<='1371844800';
 num | value_avg |   clock    
-----+-----------+------------
  60 |        56 | 1371841200
  60 |        58 | 1371844800
(2 rows)

Inaccuracy: -9,5% trends 1 hour

Can anyone verify this?

[roman-sh]

Imprecision calculation value_avg in trends_uint? (Zabbix-2.0.5 + Postgresql-9.0.1)

Bug report "trend calculation utterly broken for unsigned values":

https://support.zabbix.com/browse/ZBX-3643

Thread can be closed.

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