1.6.2 - charts page does not open

[urvancevav]

Then I try to open monitoring->charts, that occurs nothing.
On postgres i see long-running query:

select t.itemid, t.clock from trends t where itemid in (45430,45432) order by t.itemid, t.clock limit 1;

The problem in

limit 1

part.
Without that query executed instantly.

I use PostgreSQL 8.3.6 on x86_64-pc-linux-gnu, compiled by GCC gcc-4.3.real (Ubuntu 4.3.2-1ubuntu12) 4.3.2

[Aly]

You mean that "limit 1" is a source of a problem??? Very interesting why..

[urvancevav]

You mean that "limit 1" is a source of a problem??? Very interesting why..

Don't known why. But query with "limit 1" superimposes exclusive locking

[Aly]

This what I've found:

Limit would have tried to fetch two rows from the underlying plan.
If only one matching row is actually available, this would result in
scanning the whole source table.

This comment dated by 2002.. I hardly believe that this issue is still unresolved. But my tests on pgsql 8.3.1 behaves exactly in this manner

[urvancevav]

I found this thread, dated by 2008:

http://www.nabble.com/limit-clause-produces-wrong-query-plan-td20651320.html

looks that is postrges bug.

P.S. This query executes very quickly:

select t.itemid, t.clock from trends t where itemid=45432 order by t.itemid, t.clock limit 1;