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Re: MS Access and #deleted due to timeouts

From: "Zlatko Matic" <zlatko(dot)matic1(at)sb(dot)t-com(dot)hr>
To: "Greg Campbell" <greg(dot)campbell(at)us(dot)michelin(dot)com>,"Pgsql-Odbc (E-mail)" <pgsql-odbc(at)postgresql(dot)org>
Subject: Re: MS Access and #deleted due to timeouts
Date: 2005-07-12 22:35:39
Message-ID: 011501c58732$096ab5b0$e4321dc3@zlatko58zaczpv (view raw or flat)
Thread:
Lists: pgsql-odbc
Hi!

There is an article on MSDN about #deleted (see below), maybe it will help 
you to better understand the problem.

I experienced a lot of pain with my tables caused by #deleted, but I have 
solved it by simple adding numeric bigserial field as primary keys in all my 
tables.
There is no #deleted anymore.
http://support.microsoft.com/default.aspx?scid=kb;en-us;128809
ACC: "#Deleted" Errors with Linked ODBC Tables
View products that this article applies to.
      Article ID : 128809
      Last Review : May 6, 2003
      Revision : 1.0

This article was previously published under Q128809
On This Page
     SYMPTOMS
     CAUSE
     RESOLUTION
     MORE INFORMATION
         Steps to Reproduce Behavior
     APPLIES TO

SYMPTOMS
When you retrieve, insert, or update records in a linked ODBC table, each 
field in a record contains the "#Deleted" error message. When you retrieve, 
insert, or update records using code, you receive the error message "Record 
is deleted."
     Back to the top

CAUSE
The Microsoft Jet database engine is designed around a keyset-driven model. 
This means that data is retrieved, inserted, and updated based on key values 
(in the case of a linked ODBC table, the unique index of a table).

After Microsoft Access performs an insert or an update of a linked ODBC 
table, it uses a Where criteria to select the record again to verify the 
insert or update. The Where criteria is based on the unique index. Although 
numerous factors can cause the select not to return any records, most often 
the cause is that the key value Microsoft Access has cached is not the same 
as the actual key value on the ODBC table. Other possible causes are as 
follows:
      . Having an update or insert trigger on the table, modifying the key 
value.
      . Basing the unique index on a float value.
      . Using a fixed-length text field that may be padded on the server 
with the correct amount of spaces.
      . Having a linked ODBC table containing Null values in any of the 
fields making up the unique index.
These factors do not directly cause the "#Deleted" error message. Instead, 
they cause Microsoft Access to go to the next step in maintaining the key 
values, which is to select the record again, this time with the criteria 
based on all the other fields in the record. If this step returns more than 
one record, Microsoft Access returns the "#Deleted" message because it does 
not have a reliable key value to work with. If you close and re-open the 
table or choose Show All Records from the Records menu, the "#Deleted" 
errors are removed.

Microsoft Access uses a similar process to retrieve records from an linked 
ODBC table. First, it retrieves the key values and then the rest of the 
fields that match the key values. If Microsoft Access is not able to find 
that value again when it tries to find the rest of the record, it assumes 
that the record is deleted.
     Back to the top

RESOLUTION
The following are some strategies that you can use to avoid this behavior:
      . Avoid entering records that are exactly the same except for the 
unique index.
      . Avoid an update that triggers updates of both the unique index and 
another field.
      . Do not use a Float field as a unique index or as part of a unique 
index because of the inherent rounding problems of this data type.
      . Do all the updates and inserts by using SQL pass-through queries so 
that you know exactly what is sent to the ODBC data source.
      . Retrieve records with an SQL pass-through query. An SQL pass-through 
query is not updateable, and therefore does not cause "#Delete" errors.
      . Avoid storing Null values within any field making up the unique 
index of your linked ODBC table.

     Back to the top

MORE INFORMATION
Note: In Microsoft Access 2.0, linked tables were called attached tables.
     Back to the top

Steps to Reproduce Behavior

      1. Open the sample database Northwind.mdb (or NWIND.MDB. in Microsoft 
Access 2.0)
      2. Use the Upsizing Tools to upsize the Shippers table.

      NOTE: This table contains an AutoNumber field (or Counter field in 
Microsoft Access 2.0) that is translated on SQL Server by the Upsizing Tools 
into a trigger that emulates a counter.
      3. Open the linked Shippers table and enter a new record. Make sure 
that the record you enter has the same data in the Company Name field as the 
previous record.
      4. Press TAB to move to a new record. Note that the "#Deleted" error 
fills the record you entered.
      5. Close and re-open the table. Note that the record is correct.

     Back to the top


--------------------------------------------------------------------------------

APPLIES TO
      . Microsoft Access 2.0 Standard Edition
      . Microsoft Access 95 Standard Edition
      . Microsoft Access 97 Standard Edition

     Back to the top

      Keywords:  kberrmsg kbinterop kbprb KB128809

----- Original Message ----- 
From: "Greg Campbell" <greg(dot)campbell(at)us(dot)michelin(dot)com>
To: "Pgsql-Odbc (E-mail)" <pgsql-odbc(at)postgresql(dot)org>
Sent: Wednesday, July 13, 2005 12:16 AM
Subject: [ODBC] MS Access and #deleted due to timeouts


>I have distinctly noticed that when I leave my Access database with
> PostgreSQL linked tables for any considerable length of time, all fields
> in ALL linked tables say #deleted in data table view (and I'd assume
> form view as well).
>
>
> Notes:
> I have OIDS and Primary keys on the tables. Access is aware of this. And
> I have row versioning turned on.
>
> Troubleshooting:
> I turned on the ODBC trace.
> What I see is a simple select query does a SQLExecDirectW (e.g. "SELECT
> "public"."employees"."first_name" from "public"."employees" /0").
> Then it does an SQLFetch and SQLGetData for each row. (No obvious data
> returned).
>
> Then it does a SQLPrepareW that look like
> "SELECT "public"."employees"."first_name" FROM "public"."employees"
> WHERE  "emp_id"=? or "emp_id"=? or "emp_id"=? or "emp_id"=? or
> "emp_id"=? or "emp_id"=? or "emp_id"=? or "emp_id"=? or "emp_id"=? or
> "emp_id"=? \0"
>
> Then it does a SQLBindParamter for each of the 10 instance of emp_id.
> Why it enumerates the same paramter 10 times is a mystery to me.
>
> Then it does a fetch and three (3) SQLGetDatas for each row.
> I don't know what the first ones doing. The 2nd returns data,data_type,
> data_length. The 3rd,...well I'm not sure what that one's doing.
>
> In data view I see my data.
>
> Then I let 20 or 30 minutes pass.
>
> Same as above, except after binding parameters, my first fetch returns a
> code 100 (SQL_NO_DATA_FOUND).
> In the data view I see a #deleted for each record.
>
> Here are my question?
> 1. Are two passes of fetches absolutely necessary each time I run my 
> query?
> 2. What's up with all the parameters to my primary key.
> 3. I noticed that my connection handle (HSTMT) was the same before and
> after my 30 minute time-out. Could the Postgresql server have timed out
> my connection while my ODBC driver still thinks it is a viable
> connection, and tries to re-use it?
> 4. What the best way to handle this open connection pooling? My general
> practice has been that very short lived connections are good (say a
> minute or so), but I am not sure if that applies with a thick client
> like Access.
>
>
>
>
>


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