Re: [GENERAL] Re: Cannot retrieve images inserted through VB and odbc, after a table reorganization. - Mailing list pgsql-general

Thanks, Adrian for the response.

Yes, we are using the "large object" as per the specifications in the special "lo" module that we installed on the backend server. The table is created using the "lo" datatype for the image field and the table is being regularly used for insertions and retrievals using utilities other than ones using odbc. The odbc connection, too, works well on the table, as long as the table data is not reorganized after insertion(s).

Here are three pages of our postgres odbc driver settings. Sorry, they are screen captures,  not plain text!

Alanoly.

-----Original Message-----
From: Adrian Klaver [mailto:adrian.klaver@aklaver.com]
Sent: Thursday, September 04, 2014 9:39 AM
To: Alanoly Andrews; 'Craig James'
Cc: pgsql-admin@postgresql.org; pgsql-general@postgresql.org
Subject: Re: [GENERAL] Re: [ADMIN] Cannot retrieve images inserted through VB and odbc, after a table reorganization.

On 09/04/2014 05:56 AM, Alanoly Andrews wrote:

> Hi Adrian,

> 

> Thanks for that explanation of how the "relfilenode" changes after a table reorganization. It is not surprising that this happens because the table rows are being physically moved from one location to another. But such changes at the backend should be transparent to the end user. The VB code at the client side runs a simple sql like "select image from image_table where image_key=somevalue". There is no reference to postgres-specific internal variables like "oid" and "relfilenode". I do not know the inner workings of the postgres odbc driver; but I would be surprised if it works at the granularity of "oid" and "relfilenode" and that it would store the actual physical values of relfilenode (which would keep changing after every table reload, reorg etc.).

In addition to what David mentioned, some more detail on what you are calling a 'large object'.  In Postgres there is not really a 'large object' type(though I am guilty of saying there is), instead there is a way of working with large objects outside of the bytea type. Now in the ODBC FAQ there is a recipe for creating a 'lo' type:

http://psqlodbc.projects.pgfoundry.org/faq.html#4.4

Is this what you are using?

If not how are you working with the large objects?

Also given that you are working with the Postgres ODBC driver, you might want to break the cross post rule and ask this question on the psql-odbc

list:

http://www.postgresql.org/list/pgsql-odbc/

In any case your ODBC settings would be helpful.

> 

> Alanoly.

> 

--

Adrian Klaver

adrian.klaver@aklaver.com