Re: [ODBC] ODBC connections go dead after a failed query?

On 03/03/2017 12:14 PM, Jack C. Wei wrote:
> Hi,
>
> We have some legacy SQL queries that works on SQL Server but not on
> PostgreSQL due to SQL Server-specific syntax, which we are working to
> migrate. The problem is sometimes psqlodbc just cannot seem to reset
> itself after a bad query and simply go dead. All subsequent queries on
> the same connection, legitimate or not, would fail.
>
> I've verified this can happen with the latest PostgreSQL 9.6.2 and
> psqlodbc 09_06_0100, on a Windows 7 x64 host.
>
> The offending SQL query is something like "UPDATE site SET
> image=image_old;" where [image] is BYTEA (used to be MEDIUMBLOB on SQL
> Server) and [image_old] is TEXT. PostgreSQL does not allow this, which
> is understandable. But after this query the connection goes dead,
> failing all subsequent queries with ODBC error 08S01 or HY000. While it
> is possible to detect this and reconnect as a workaround, it would be
> cumbersome and lead to unwarranted overhead. See the following excerpt
> from my ODBC trace log:
>
>
> PsqlOdbcBug     f68-e10    EXIT  SQLPrepareW  with return code 0
> (SQL_SUCCESS)
>         HSTMT               0x00033EE8
>         WCHAR *             0x010F0F28 [      -3] "UPDATE site SET
> image=image_old;\ 0"
>         SDWORD                    -3
>
> PsqlOdbcBug     f68-e10    ENTER SQLExecute
>         HSTMT               0x00033EE8
>
> PsqlOdbcBug     f68-e10    EXIT  SQLExecute  with return code -1 (SQL_ERROR)
>         HSTMT               0x00033EE8
>
>         DIAG [42804] ERROR: column "image" is of type bytea but
> expression is of type text;
> Error while preparing parameters (1)
>
> PsqlOdbcBug     f68-e10    ENTER SQLFreeHandle
>         SQLSMALLINT                  3 <SQL_HANDLE_STMT>
>         SQLHANDLE           0x00033EE8
>
> PsqlOdbcBug     f68-e10    EXIT  SQLFreeHandle  with return code 0
> (SQL_SUCCESS)
>         SQLSMALLINT                  3 <SQL_HANDLE_STMT>
>         SQLHANDLE           0x00033EE8
>
> PsqlOdbcBug     f68-e10    ENTER SQLAllocHandle
>         SQLSMALLINT                  3 <SQL_HANDLE_STMT>
>         SQLHANDLE           0x000338D8
>         SQLHANDLE *         0x0035EB90
>
> PsqlOdbcBug     f68-e10    EXIT  SQLAllocHandle  with return code 0
> (SQL_SUCCESS)
>         SQLSMALLINT                  3 <SQL_HANDLE_STMT>
>         SQLHANDLE           0x000338D8
>         SQLHANDLE *         0x0035EB90 ( 0x00D51C98)
>
> PsqlOdbcBug     f68-e10    ENTER SQLPrepareW
>         HSTMT               0x00D51C98
>         WCHAR *             0x010F0DE0 [      -3] "SELECT id FROM site;\ 0"
>         SDWORD                    -3
>
> PsqlOdbcBug     f68-e10    EXIT  SQLPrepareW  with return code 0
> (SQL_SUCCESS)
>         HSTMT               0x00D51C98
>         WCHAR *             0x010F0DE0 [      -3] "SELECT id FROM site;\ 0"
>         SDWORD                    -3
>
> PsqlOdbcBug     f68-e10    ENTER SQLExecute
>         HSTMT               0x00D51C98
>
> PsqlOdbcBug     f68-e10    EXIT  SQLExecute  with return code -1 (SQL_ERROR)
>         HSTMT               0x00D51C98
>
>         DIAG [08S01] Could not send Query(connection dead);
> Could not send Query(connection dead) (26)
>
>
> I've attached a minimal working sample code (we develop in Visual Studio
> 2013) and also the ODBC trace log. Hopefully they make it through. Any
> feedback is welcome.

I am betting you dealing with something like this:

test=> begin ;
BEGIN
test=> select 1/0;
ERROR:  division by zero
test=> select 1;
ERROR:  current transaction is aborted, commands ignored until end of
transaction block
test=> rollback ;
ROLLBACK
test=> select 1;
  ?column?
----------
         1
(1 row)

Basically an error in a transaction stops everything until you rollback.

Here:
https://odbc.postgresql.org/docs/config.html

there is :

Level of rollback on errors: Specifies what to rollback should an error
occur.


     Nop(0): Don't rollback anything and let the application handle the
error.

     Transaction(1): Rollback the entire transaction.

     Statement(2): Rollback the statement.


     Notes in a setup: This specification is set up with a PROTOCOL
option parameter.

     PROTOCOL=[6.2|6.3|6.4|7.4][-(0|1|2)]
     default value is a sentence unit (it is a transaction unit before 8.0).

I have never used that, so I am not sure exactly how  to invoke it and
what the consequences are.



>
>
> Thank you,
> Jack Wei
>
>
>
>
>


--
Adrian Klaver
adrian.klaver@aklaver.com