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List:       postgresql-general
Subject:    Re: [GENERAL] Unhandled exception in PGAdmin when opening 16-million-record
From:       Guillaume Lelarge <guillaume () lelarge ! info>
Date:       2010-10-31 6:22:37
Message-ID: 4CCD0B2D.4010806 () lelarge ! info
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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

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