VC/Database, MSSQL & ADO & threads ???!!

MSSQL & ADO & threads ???!!

Author	Message
Adam Gro #1 / 9	MSSQL & ADO & threads ???!! Hi! I try to use ADO to work with MSSQL Server but ... Is it possible to use one Connection object declared globaly in many threads concurently ? I'd like to get 1 connection to SQL server instead of ~100 from every running thread. So now I declare 1 Connection object per thread & establish separate connection from within (by method Open). I've found that such a solution is possible till ~64 threads. Every next doesn't work though it doesn't return any error ! ?? ps -- Adam Gros _________/)____/)_/)__/)____
Sun, 08 Sep 2002 03:00:00 GMT

Adam Gro #2 / 9	MSSQL & ADO & threads ???!! Hi! I've forgot to write that I try to do it with VC++ 6.0 :-) Quote: > Hi! > I try to use ADO to work with MSSQL Server but ... > Is it possible to use one Connection object declared globaly in many > threads concurently ? > I'd like to get 1 connection to SQL server instead of ~100 from every > running thread. > So now I declare 1 Connection object per thread & establish separate > connection from within (by method Open). > I've found that such a solution is possible till ~64 threads. Every next > doesn't work though it doesn't return any error ! ?? > ps > -- > Adam Gros > _________/)____/)_/)__/)____ -- Adam Gros _________/)____/)_/)__/)____
Sun, 08 Sep 2002 03:00:00 GMT

John Fishe #3 / 9	MSSQL & ADO & threads ???!! Adam, I've used ADO connections to SQL in several different threads. However, you cannot use a connection by more than one thread at a time. You'll need each thread to somehow lock the connection (from some kind of pool), use it till the thread is done, then unlock the connection for another thread to use. John Quote: > Hi! > I've forgot to write that I try to do it with VC++ 6.0 :-) > > Hi! > > I try to use ADO to work with MSSQL Server but ... > > Is it possible to use one Connection object declared globaly in many > > threads concurently ? > > I'd like to get 1 connection to SQL server instead of ~100 from every > > running thread. > > So now I declare 1 Connection object per thread & establish separate > > connection from within (by method Open). > > I've found that such a solution is possible till ~64 threads. Every next > > doesn't work though it doesn't return any error ! ?? > > ps > > -- > > Adam Gros > > _________/)____/)_/)__/)____ > -- > Adam Gros > _________/)____/)_/)__/)____
Sun, 08 Sep 2002 03:00:00 GMT

Hemo #4 / 9	MSSQL & ADO & threads ???!! ADO is thread safe (at least that's what the doc says). I used 1 connection between multiple threads all the time (use a ConnectionPtr). Just be careful on how you reopen the connection if it fails (i.e., thread safe code). You don't want 50 threads all trying to reopen the same connection at the same time. Quote: > I try to use ADO to work with MSSQL Server but ... > Is it possible to use one Connection object declared globaly in many > threads concurently ? > I'd like to get 1 connection to SQL server instead of ~100 from every > running thread. > So now I declare 1 Connection object per thread & establish separate > connection from within (by method Open). > I've found that such a solution is possible till ~64 threads. Every next > doesn't work though it doesn't return any error ! ?? > ps > -- > Adam Gros > _________/)____/)_/)__/)____
Sun, 08 Sep 2002 03:00:00 GMT

Hemo #5 / 9	MSSQL & ADO & threads ???!! I had read that ADO was completely thread safe. Is that not true? I always assumed I could do 2 Execute statements in 2 different threads at the same time on the same connection. I just assumed that ADO would "queue" the SQL operations if it couldn't process them in parallel. Hum, if not, then I had better add some thread safe code in...I better go test this out! Quote: > Adam, > I've used ADO connections to SQL in several different threads. However, you > cannot use a connection by more than one thread at a time. You'll need each thread > to somehow lock the connection (from some kind of pool), use it till the thread is > done, then unlock the connection for another thread to use. > John > > Hi! > > I've forgot to write that I try to do it with VC++ 6.0 :-) > > > Hi! > > > I try to use ADO to work with MSSQL Server but ... > > > Is it possible to use one Connection object declared globaly in many > > > threads concurently ? > > > I'd like to get 1 connection to SQL server instead of ~100 from every > > > running thread. > > > So now I declare 1 Connection object per thread & establish separate > > > connection from within (by method Open). > > > I've found that such a solution is possible till ~64 threads. Every next > > > doesn't work though it doesn't return any error ! ?? > > > ps > > > -- > > > Adam Gros > > > _________/)____/)_/)__/)____ > > -- > > Adam Gros > > _________/)____/)_/)__/)____
Sun, 08 Sep 2002 03:00:00 GMT

Hemo #6 / 9	MSSQL & ADO & threads ???!! After some quick testing, ADO Connections are not thread safe (unless you call getting an exception thread safe). However, parsing Recordsets appears to be safe (at least with Forward Only cursors). It just seems like you can't have 2 queries executing queries at the same time. Nexting through 2 Recordsets over the same Connection didn't cause me any problems. In any case, thread safe code for ADO is the right answer. If I find where I read ADO was thread safe I'll publish... Quote: > I had read that ADO was completely thread safe. Is that not true? I always > assumed I could do 2 Execute statements in 2 different threads at the same > time on the same connection. I just assumed that ADO would "queue" the SQL > operations if it couldn't process them in parallel. Hum, if not, then I had > better add some thread safe code in...I better go test this out! > > Adam, > > I've used ADO connections to SQL in several different threads. > However, you > > cannot use a connection by more than one thread at a time. You'll need > each thread > > to somehow lock the connection (from some kind of pool), use it till the > thread is > > done, then unlock the connection for another thread to use. > > John > > > Hi! > > > I've forgot to write that I try to do it with VC++ 6.0 :-) > > > > Hi! > > > > I try to use ADO to work with MSSQL Server but ... > > > > Is it possible to use one Connection object declared globaly in many > > > > threads concurently ? > > > > I'd like to get 1 connection to SQL server instead of ~100 from every > > > > running thread. > > > > So now I declare 1 Connection object per thread & establish separate > > > > connection from within (by method Open). > > > > I've found that such a solution is possible till ~64 threads. Every > next > > > > doesn't work though it doesn't return any error ! ?? > > > > ps > > > > Please, send any answer to my email - Hide quoted text - - Show quoted text - Quote: > > > > -- > > > > Adam Gros > > > > _________/)____/)_/)__/)____ > > > -- > > > Adam Gros > > > _________/)____/)_/)__/)____
Sun, 08 Sep 2002 03:00:00 GMT

Adam Gro #7 / 9	MSSQL & ADO & threads ???!! It's Ok if you open 1 recordset and browse it from many threads, but what about openning different recordsets ? What I wanted to do was every thread uses its own recordset (because they can be defferent). Quote: > ADO is thread safe (at least that's what the doc says). I used 1 connection > between multiple threads all the time (use a ConnectionPtr). Just be > careful on how you reopen the connection if it fails (i.e., thread safe > code). You don't want 50 threads all trying to reopen the same connection > at the same time. > > I try to use ADO to work with MSSQL Server but ... > > Is it possible to use one Connection object declared globaly in many > > threads concurently ? > > I'd like to get 1 connection to SQL server instead of ~100 from every > > running thread. > > So now I declare 1 Connection object per thread & establish separate > > connection from within (by method Open). > > I've found that such a solution is possible till ~64 threads. Every next > > doesn't work though it doesn't return any error ! ?? > > ps > > -- > > Adam Gros > > _________/)____/)_/)__/)____ -- Adam Gros _________/)____/)_/)__/)____
Mon, 09 Sep 2002 03:00:00 GMT

Goran Pusi #8 / 9	MSSQL & ADO & threads ???!! ADODB.Connection is apartment threaded. Therefore, if one wants to use it from different threads, she has to CoMarshalInterThreadInterfaceInStream it from the creator apartment, and CoGetInterfaceAndReleaseStream from the thread that uses it. You cannot use in-process interface pointer from another thread just by sharing it in the memory, since the apartment-threaded object doesn't need to be thread-safe (and usually isn't). Doing so breaks the object. Goran.
Sun, 22 Sep 2002 03:00:00 GMT

John Fishe #9 / 9	MSSQL & ADO & threads ???!! Hi, The need for CoMarshalInterThreadInterfaceInStream() is not determined by the threading model of the interface host -- it is determined by the client's threading model. This means that if you have threads in an MTA, and decide to use an ADODB.Connection object, every one of the threads in the MTA can use the Connection interface without using CoMarshalInterThreadInterfaceInStream(). Sure, the interface/object you're using may not be thread safe. But that only means that you need to write your code carefully so that two threads don't use it simultaneously. It rarely means that only a certain thread may use it. John Quote: > ADODB.Connection is apartment threaded. Therefore, if one wants to use it > from different threads, she has to CoMarshalInterThreadInterfaceInStream it > from the creator apartment, and CoGetInterfaceAndReleaseStream from the > thread that uses it. > You cannot use in-process interface pointer from another thread just by > sharing it in the memory, since the apartment-threaded object doesn't need > to be thread-safe (and usually isn't). Doing so breaks the object. > Goran.
Sun, 22 Sep 2002 03:00:00 GMT

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