Re: Unhandled exception in PGAdmin when opening 16-million-record table

Le 29/10/2010 14:46, Guillaume Lelarge a écrit :
> Le 29/10/2010 13:52, Rob Richardson a écrit :
>> A customer was reviewing the database that supports the application we
>> have provided. One of the tables is very simple, but has over 16
>> million records. Here is the table's definition:
>>
>> CREATE TABLE feedback
>> (
>> charge integer,
>> elapsed_time integer, -- number of elapsed minutes since data began
>> recording
>> tag_type character varying(24), -- Description of tag being recorded
>> tag_value real, -- value of tag being recorded
>> status smallint, -- PLC Status, recorded with Control PV only
>> stack integer, -- Not used
>> heating smallint DEFAULT 0, -- 1 for heating, 0 for cooling
>> cooling smallint DEFAULT 0 -- not used
>> )
>>
>> As you see, there is no primary key. There is a single index, as
>> follows:
>>
>> CREATE INDEX feedback_charge_idx
>> ON feedback
>> USING btree
>> (charge);
>>
>> In PGAdmin, the customer selected this table and clicked the grid on the
>> toolbar, asking for all of the records in the table. After twenty
>> minutes, a message box appeared saying that an unhandled exception had
>> happened. There was no explanation of what the exception was. The
>> database log does not contain any information about it. The PGAdmin
>> display did show a number of records, leading me to believe that the
>> error happened in PGAdmin rather than anywhere in PostGres.
>>
>> Can anyone explain what is happening?
>>
>
> Definitely not an error in PostgreSQL. More related to pgAdmin.
>
>> The customer is using PostgreSQL 8.4.5 (we just updated them within the
>> last few days) and PGAdmin 1.10.5 on a Windows Server 2003 box.
>>
>> I see PGAdmin is now up to 1.12.1. I suppose the first thing I should
>> do is update their PGAdmin.
>>
>
> Won't do anything if your customer still wants to look at 16 million rows.
>
> The only thing we could probably do on the coding side is looking at the
> estimated number of rows and displays a warning message telling: "Hey
> dude, you're trying to look at around 16 million rows. That can't work.
> You would be very well advised to cancel.", but still allows the user to
> bypass this check (if the estimated number of rows is wrong).
>

I added a ticket on this (http://code.pgadmin.org/trac/ticket/273) so
that we can work on it at a later time.

--
Guillaume
http://www.postgresql.fr
http://dalibo.com