Re: [Quickfix-developers] QFJ: Acceptors and SessionQualifiers

[Steve B. <st...@te...>]

Oracle treats an empty string as a null. :-(

Steve

Oren Miller wrote:
> QuickFIX Documentation: 
> http://www.quickfixengine.org/quickfix/doc/html/index.html
> QuickFIX Support: http://www.quickfixengine.org/services.html
> 
> Yeah, the way it is implemented right now, is that any sessionID  
> "without" a session qualifier, has a blank string as the qualifier.   
> Which as noted allows us to make it part of the primary key.   In the  
> java wrappers for the C++ engine, the constructor for a sessionID  
> without a qualifier looks like this:
> 
> public SessionID(String beginString,
>                                 String senderCompID,
>                                 String targetCompID) {
>     create( beginString, senderCompID, targetCompID, "" )
> }
> 
> So you can see that a blank string is being assigned.  It looks like  
> QuickFIX/J does the same thing with its sessionID.  So far I'm not  
> aware of any problems this caused with the direct SQL implementations  
> I've seen (MySQL, PostgreSQL, MSSQL).   If this is a problem, I'd be  
> surprised if it was an acceptor only problem, since most initiator  
> sessions are also created with blank session qualifiers unless they  are 
> specifically added.  Are there really databases you know of that  cannot 
> differentiate between a NULL and a blank string?
> 
> --oren
> 
> On Oct 7, 2005, at 2:31 AM, Steve Bate wrote:
> 
>> QuickFIX Documentation: http://www.quickfixengine.org/quickfix/doc/ 
>> html/index.html
>> QuickFIX Support: http://www.quickfixengine.org/services.html
>>
>> Hi Toby,
>>
>> The session qualifier is logically part of the primary key that
>> uniquely identifies a session. Multiple sessions can have the
>> same begin string, target/sender company identifiers. This is
>> also the way the QF C++ code is designed. You won't be able
>> to remove the "not null" constraint for session qualifier
>> without removing it from the primary key -- and that probably
>> isn't a good thing.
>>
>> The SQL schema used by QFJ is the same one that the QF C++
>> code uses. However, there might be some additional issues in
>> QFJ because it supports any JDBC database rather than just
>> MySQL. Which database are you using? Is the session qualifier
>> a Java null or an empty string? Some databases will convert
>> an empty string to a NULL value when inserting a row into the
>> database, so either way it could be a problem in some cases.
>>
>> Oren, any additional comments?
>>
>> Steve
>>
>>
>> Shepheard, Toby (London) wrote:
>>
>>> QuickFIX Documentation:
>>>
>> http://www.quickfixengine.org/quickfix/doc/html/index.html
>>
>>> QuickFIX Support: http://www.quickfixengine.org/services.html
>>>
>>> NB:  This is using QuickFIX/J (1.0.0-beta1) with a minor fix from CVS
>>> for FileLog.java
>>>
>>> I came across a problem when running as an Acceptor with the JDBC
>>> message store (JDBCStore.java), and the fact that the  SessionQualifier
>>> is null for Acceptors, but is required in the database tables. See
>>> http://www.quickfixengine.org/bugtracker/bug.php?op=show&bugid=115
>>>
>>> Am I missing something here or is this a problem with QFJ - and are
>>> SessionQualifiers really needed? From what I can see they look like
>>> they're meant to be optional for initiators, and meaningless for
>>> acceptors, but I'm not at all sure.
>>>
>>> As far as I can see I've got two options - either add a session
>>> qualifier to the acceptor config, or alter the DB and JDBCStore  code to
>>> not require a session qualifier (which has a rather large impact  due to
>>> the primary key changes that would entail). I hope someone can  advise!
>>>
>>> Many thanks,
>>> Toby
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>>
>>
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