Multiple writers / rowlocking

Hi,

I am implementing an app that will do massive updating on a DataTable
with multiple threads. Typically I first look up the row:

DataRow row = mydatatable.Rows.Find(key);

and then do some updating:

row.BeginEdit(); // here is where I get the exception

foreach (string colname in collist)
row[colname]=mydatacollection[colname];

row.EndEdit();

The problem is: in a multithreaded scenario the "BeginEdit" method
will raise an exception if the row is already being updated by another
thread. At least that's how the it looks to me. So I put a lock on the
row

lock (row)
{
row.BeginEdit();
....

but that didn't help. I could not find special sync objects on the row
level, so does someone know an efficient way to get this exception
over with?

Thanks in advance for any suggestion,

DC

I spent quiet some time trying to fix this - to no avail. I believe
that the RecordManager of the SqlData classes is buggy when it comes
to massive multiple writers. I tried synchronizing with the only
object that I found supporting synchronization in these classes:
DataRowCollection. While putting a lock on DatarowCollection.SyncRoot
does produce less exceptions, it sooner or later will. Also, locking
the whole table is a bit coarse for my application, I need locks on
the row level.

The exception I get is a NullReferenceException

at System.Data.RecordManager.NewRecordBase()
at System.Data.DataTable.NewRecord(Int32 sourceRecord)
at System.Data.DataRow.BeginEdit()
at System.Data.DataRow.set_Item(DataColumn column, Object value)
at System.Data.DataRow.set_Item(String columnName, Object value)
...(my method)

I will now start writing my own datahousekeeping class for this.

Regards

DC


dc@upsize.de (DC) wrote in message news:<5b7bac12.0306300830.4d7edd79@posting.google.com>...
> Hi,
>
> I am implementing an app that will do massive updating on a DataTable
> with multiple threads. Typically I first look up the row:
>
> DataRow row = mydatatable.Rows.Find(key);
>
> and then do some updating:
>
> row.BeginEdit(); // here is where I get the exception
>
> foreach (string colname in collist)
> row[colname]=mydatacollection[colname];
>
> row.EndEdit();
>
> The problem is: in a multithreaded scenario the "BeginEdit" method
> will raise an exception if the row is already being updated by another
> thread. At least that's how the it looks to me. So I put a lock on the
> row
>
> lock (row)
> {
> row.BeginEdit();
> ...
>
> but that didn't help. I could not find special sync objects on the row
> level, so does someone know an efficient way to get this exception
> over with?
>
> Thanks in advance for any suggestion,
>
> DC

http://users.pandora.be/pdo


please send me a personal email if you want to join in the development of
this project...


grtz

Kris



"DC" <dc@upsize.de> wrote in message
news:5b7bac12.0307020115.335612fa@posting.google.com...
> I spent quiet some time trying to fix this - to no avail. I believe
> that the RecordManager of the SqlData classes is buggy when it comes
> to massive multiple writers. I tried synchronizing with the only
> object that I found supporting synchronization in these classes:
> DataRowCollection. While putting a lock on DatarowCollection.SyncRoot
> does produce less exceptions, it sooner or later will. Also, locking
> the whole table is a bit coarse for my application, I need locks on
> the row level.
>
> The exception I get is a NullReferenceException
>
> at System.Data.RecordManager.NewRecordBase()
> at System.Data.DataTable.NewRecord(Int32 sourceRecord)
> at System.Data.DataRow.BeginEdit()
> at System.Data.DataRow.set_Item(DataColumn column, Object value)
> at System.Data.DataRow.set_Item(String columnName, Object value)
> ...(my method)
>
> I will now start writing my own datahousekeeping class for this.
>
> Regards
>
> DC
>
>
> dc@upsize.de (DC) wrote in message
news:<5b7bac12.0306300830.4d7edd79@posting.google.com>...
> > Hi,
> >
> > I am implementing an app that will do massive updating on a DataTable
> > with multiple threads. Typically I first look up the row:
> >
> > DataRow row = mydatatable.Rows.Find(key);
> >
> > and then do some updating:
> >
> > row.BeginEdit(); // here is where I get the exception
> >
> > foreach (string colname in collist)
> > row[colname]=mydatacollection[colname];
> >
> > row.EndEdit();
> >
> > The problem is: in a multithreaded scenario the "BeginEdit" method
> > will raise an exception if the row is already being updated by another
> > thread. At least that's how the it looks to me. So I put a lock on the
> > row
> >
> > lock (row)
> > {
> > row.BeginEdit();
> > ...
> >
> > but that didn't help. I could not find special sync objects on the row
> > level, so does someone know an efficient way to get this exception
> > over with?
> >
> > Thanks in advance for any suggestion,
> >
> > DC

Hi Kris,

interesting project but not exactly what I am into. My apps (dealing
with realtime information) usually work with data as dirty as possible
with as little rowlocking as possible - pessimistic rowlocking is the
worst I can run into.

I replaced the DataTable I used to store information with a class
derived from Hashtable and that threads great now. I can only
recommend to any ADO.NET users: if you really don't require many of
the ADO.NET classes' features and require multiple writers in a
mutithreaded scenario, then you are probably better off designing your
own class for this purpose; took me a couple of hours after debugging
the DataRow updating for three days. Even filling my class with data
(using an SqlDataReader) performs better than filling a DataTable with
the SqlAdapter since my class only produces the overhead I actually
need.

Regards

DC

"Kris" <kris_de_greve@hotmail.com> wrote in message news:<OcXDQrKQDHA.2228@tk2msftngp13.phx.gbl>...
> http://users.pandora.be/pdo
>
>
> please send me a personal email if you want to join in the development of
> this project...
>
>
> grtz
>
> Kris
>
>
>
> "DC" <dc@upsize.de> wrote in message
> news:5b7bac12.0307020115.335612fa@posting.google.com...
> > I spent quiet some time trying to fix this - to no avail. I believe
> > that the RecordManager of the SqlData classes is buggy when it comes
> > to massive multiple writers. I tried synchronizing with the only
> > object that I found supporting synchronization in these classes:
> > DataRowCollection. While putting a lock on DatarowCollection.SyncRoot
> > does produce less exceptions, it sooner or later will. Also, locking
> > the whole table is a bit coarse for my application, I need locks on
> > the row level.
> >
> > The exception I get is a NullReferenceException
> >
> > at System.Data.RecordManager.NewRecordBase()
> > at System.Data.DataTable.NewRecord(Int32 sourceRecord)
> > at System.Data.DataRow.BeginEdit()
> > at System.Data.DataRow.set_Item(DataColumn column, Object value)
> > at System.Data.DataRow.set_Item(String columnName, Object value)
> > ...(my method)
> >
> > I will now start writing my own datahousekeeping class for this.
> >
> > Regards
> >
> > DC
> >
> >
> > dc@upsize.de (DC) wrote in message
> news:<5b7bac12.0306300830.4d7edd79@posting.google.com>...
> > > Hi,
> > >
> > > I am implementing an app that will do massive updating on a DataTable
> > > with multiple threads. Typically I first look up the row:
> > >
> > > DataRow row = mydatatable.Rows.Find(key);
> > >
> > > and then do some updating:
> > >
> > > row.BeginEdit(); // here is where I get the exception
> > >
> > > foreach (string colname in collist)
> > > row[colname]=mydatacollection[colname];
> > >
> > > row.EndEdit();
> > >
> > > The problem is: in a multithreaded scenario the "BeginEdit" method
> > > will raise an exception if the row is already being updated by another
> > > thread. At least that's how the it looks to me. So I put a lock on the
> > > row
> > >
> > > lock (row)
> > > {
> > > row.BeginEdit();
> > > ...
> > >
> > > but that didn't help. I could not find special sync objects on the row
> > > level, so does someone know an efficient way to get this exception
> > > over with?
> > >
> > > Thanks in advance for any suggestion,
> > >
> > > DC

Hi DC,
Can u share out yr class code to me as i am facing yr problem as well. Thanks in advance. My email is woosweehong@yahoo.com

Regards,
Woo