Do I need to lock a table during a FLUSH when using VSDK C++ API in multi-threaded app?

[Ivan Smahin]

Hello Matthew,

Wednesday, August 16, 2006, 11:23:55 AM, you wrote:

> On Aug 16, 2006, at 12:03 AM, Ivan Smahin wrote:

>> Hello Matthew,
>>
>> Wednesday, August 16, 2006, 12:42:43 AM, you wrote:
>>
>>> Hello,
>>
>>> I am using the VSDK 2 C++ in a multi-threaded application on a
>>> Macintosh.
>>
>>> I normally use the API way to work with the database tables, so I
>>> make sure
>>> that I use semaphores/locks on each individual table whenever I
>>> either read, modify, or add records.
>>
>>> My question is this:
>>> If I do a flush() on a database, do I need to lock the tables
>>> contained in that database
>>> to prevent other threads from potentially attempting to read, modify,
>>> or add records at the same time?
>>> Or is the flush() operation implemented so that it does not interfere
>>> with other threads
>>> potentially accessing the tables contained in the database being
>>> flushed?
>>
>>> What are the rules about locking tables for exclusive access now that
>>> Valentina 2 now
>>> is more thread-friendly?
>>
>>
>> Currently  you  need lock/unlock every "kernel" object to make sure be
>> threading  safe.  So,  for  now,  global  mutex  seems to be most safe
>> solution.
>>

> Ivan,

> When you say I need to lock/unlock every "kernel" object, what does  
> that mean exactly?

Assume   you   get   some  table  pointer (pT1) and some field pointer
( pF1 = pT1->get_Field(1) ).

The first thread call pT1->Drop_Field(1);
The second thread call pf1->get_Value();

It's just pseudo-code, but I think you will get the idea...
So  it  is  not  enough to lock pT1 for threading-safe call of table's
methods.  Because  another thread may use unlocked pF1 pointer. And so
on...

A lot of really possible scenarios could be imaging...

So I would say - for now Valentina is threading unsafe. If you want to
use it in multithreaded environment you need to use some global-guard
policy.

Again, I'm about 100% threading-safe solution.



-- 
Best regards,
 Ivan                            mailto:ivan_smahin ÎÁ valentina-db.com