Multiple writers / rowlocking

[DC]

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

 

[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

 

[Kris]

http://users.pandora.be/pdo


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


grtz

Kris

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


(e-mail address removed) (DC) wrote in message

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

 

[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

http://users.pandora.be/pdo


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


grtz

Kris

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


(e-mail address removed) (DC) wrote in message

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

 

[shwoo79]

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 (e-mail address removed)

Regards,
Woo