In my application I want to know the execution time for a stored procedure.
My pattern is to execute reader and get the data reader and read the results. The reader return immediately and I don’t know the stored procedure execution time.
I cannot put the timers after the reader because I want to have an extension method to encapsulate just the execute reader call.
Do you have any idea how I can achieve that?
Thanks,
Radu
That's not possible with a datareader because the datareader won't actually get the data untill you start reading from it.
Related
I want to build a CEP-Engine which is dynamic so you can add different event streams. As soon as a new stream is added, Esper should be able to read all the properties of the stream and put it into a list, for example. (For example integer id, long temperature, date timestamp etc.)
Is this possible in Esper?
Would be very grateful for any help
In order to add a stream at runtime you can use create-schema.
create schema MyStream(id int, ...)
For a stream that accepts events that an application sends using EPEventServive#sendEvent you should add the bus and public annotation (or set the equivalent compiler flags).
#public #buseventtype create schema MyStream(id int, ...)
You can now use this stream.
select * from MyStream
You can attach a listener and have it do some logic.
The Esper examples have a lot of detail. The create-schema is used in the "runtimeconfig" example.
Thank you for answering. I'm afraid I didn't make myself clear. I want to be able to add event streams where I don't know beforehand what kind of properties the events have. So I don't know before if there is an integer ID or if there is a date timestamp and which payload might be there. As soon as I add such an unknown event, Esper should examine the stream and return the contained properties of the stream to me.
Currently I'm using Eventstore (by Greg Young) for my company project. In my read model, I store the processed event ids, not the event name. How can I find the event in Eventstore using its Id?
I don't think this is possible currently. I think you have two choices:
in your read model store the stream and index, or the commit/prepare position of the event and then read the event from either the $all stream using the commit/prepare position or from the stream it was written to using the stream and index. This is probably the simplest.
Or create a projection in event store which indexes the events by their id and reprojects into a stream called, say, eventid-{event.id} then you can read directly from this stream.
The second is backwards compatible with your current read model, but I'm not sure is the right thing to do, as projections cause write amplification, and you probably need to make sure you exclude system events from being projected.
You can query the event using the following URL path. This will return the event and the last 20 events before it
{youreventstoredomain}:2113/web/index.html#/streams/$ce-{streamname}/{eventnumber}/backward/20
I've not been able to find an answer on this anywhere. Using Delphi XE7 with TClientDataSet, DataSnap & SQL Server. I need to insert a record, apply updates and then refresh that record so I can get the Id and assign it to my object. Seems pretty basic requirement, but on the contrary it is proving to be a royal pain.
I've found the obvious stuff on EDN, SO and Dr Bob:
http://edn.embarcadero.com/article/20847
DataSnap and the autoinc field
http://www.drbob42.com/examines/examinC0.htm
However these seem to focus on a "Refresh" of the TClientDataSet to re-fetches the entire table/query. Whilst this does actually resolve the Id field itself (good!), it also moves the cursor off the current record which was just inserted and so I'm not able to get the Id and assign it to my object. Also, for performance over HTTP I don't really want to refetch the entire table every time a record is inserted, if there's 10,000 records this will consume too much bandwidth and be ridiculously slow!
Consider the following code:
function TRepository<I>.Insert(const AEntity: I): I;
begin
FDataSet.DisableControls;
try
FDataSet.Insert;
AssignEntityToDataSet(AEntity); // SET'S ALL THE RELEVANT FIELDS
FDataSet.Post;
FDataSet.ApplyUpdates(-1);
FDataSet.Refresh; // <--- I tried RefreshRecord here but it cannot resolve the record
AEntity.Id := FDataSet.FieldByName('Id').AsInteger; // <----- THIS NOW POINTS TO WRONG ROW
finally
FDataSet.EnableControls;
end;
end;
Does anyone know how to achieve this? I need to be able to refresh and stay on the current record otherwise I do not know the Id of the record just created and the GUI cannot stay focused on the current record.
Hopefully something obvious I'm missing.
Cheers.
Rick.
Assuming you can get hands on the new ID inside the AfterUpdateRecord event of your DataProvider, your event handler then may look like this (the current record of DeltaDS is the one just inserted into SourceDS):
if (UpdateKind = ukInsert) then begin
DeltaDS.FindField('Id').NewValue := <TheNewID>;
end;
Make sure to have the poPropogateChanges option set in the provider. This will transfer the changed Id field back to the ClientDataSet.
Now you can get rid of the FDataSet.Refresh call.
SQL Server does allow you to get the last identity it generated in several ways - there's no need to "refresh" the record/query which means re-issuing a SELECT and can generate undesiderable side-effects. You can use SELECT SCOPE_IDENTITY() or use an OUTPUT clause. If the Delphi database driver supports it, TField.AutogenerateValue should accomplish that task automatically (see http://docwiki.embarcadero.com/Libraries/XE7/en/Data.DB.TField.AutoGenerateValue)
Otherwise you have to put that new data into your delta (see Raabe answer - this has to be done on the datasnap server which actually talks to the database) after reading it, so it's sent back to the client. You also need to set properly and TField.ProviderFlags to ensure data are applied correctly (see http://docwiki.embarcadero.com/RADStudio/XE7/en/Influencing_How_Updates_Are_Applied), usually you don't want those field appear in an UPDATE.
I found the "OnQueryStatement" method :
procedure TkbmMWQueryService2.kbmMWQueryServiceQueryStatement(Sender: TObject;
Place: TkbmMWQueryOperationType; var NamedQueryName, Statement: string);
begin
Form1.Memo1.Lines.Add(Statement);//show the query statement
end;
this method can get the client-side query statement,but all the client-side query trigger this event twince!(like the screenshot)!Why? How can i get the client-siade query statement correctly?
thanks in advance! :)
Its called twice on the server (in fact can be called 3 times for the same query on the server in the most far out situation).
Check the Place argument for the situation that its called in.
It can be
mwqotDefinition,mwqotQuery,mwqotExecute,mwqotResolve,mwqotMoreData,mwqotMetaData
The reason its being called multiple times when opening the query, is that the dataset first likes to get the definition (which fields and parameters will this query result in), and then the data itself.
Both the server and the client default operates like that. Hence opening a query on the client result the client in asking the server about definitions, then the client asks for the data, and that on the server may result in the server itself asking for definitions and then the data. Remember the server is stateless and default doesnt know anything about previous calls to it.
There are many ways to optimize this:
Enable caching for metadata (definitions). That will result in the cache results being used instead of the server asking the database for the definitions, and enabling the cache on the client too, results in the client not having to ask the server for definitions except first time.
Setup the AutoFieldDefs property on the query to mwafoWithData. Then the data will actually be returned at the same time as the definitions, and the 2.nd data fetch call will be skipped.
What is wrong in this code?
I was expected "titi" in person.name but I still have "toto"!
More explicitly, how to modify a record in a function?
init1()->
S=#person{name="toto"}, %record creation and field setting
fct(S),
io:format("~s~n",[S#person.name]).
fct(R)->
R#person{name="titi"}. %record updating
You need to get a result of fct():
init1()->
S=#person{name="toto"}, %record creation and field setting
S2 = fct(S), % Get updated record
io:format("~s~n",[S2#person.name]).
fct(R)->
R#person{name="titi"}. %record updating
Bertaud, I think you are getting ahead of yourself a bit. You really need to understand the basics of immutability before you write any more code. (i.e. "variables" do not vary : you can only assign a value to them once.) I suggest you read the free online guide "Learn You Some Erlang For Great Good", at http://learnyousomeerlang.com/. The section that covers the basics of variables is http://learnyousomeerlang.com/starting-out-for-real#invariable-variables.
It is impossible to stress too much that all data in Erlang is immutable. So to do something like in your original question you need to modify it like #hdima did. The record is not updated but rewritten. In the same way there is no global data in Erlang, all data belongs to a process. This is even true of ETS tables as they basically behave like a process, albeit a built-in one without explicit communication.
So if you use the process dictionary or an ETS table the data itself can never be updated, only the dictionary/table. This means that to modify some data in the dictionary/table you basically have to:
"Read" the data
Update the data making new data
"Write" the new back into the dictionary/table
Without writing the new data back into the dictionary/table it will be lost, as your new data was.
Within fct(), you're not mutating the record, but you're returning a new value for the record, which needs to be used further. If you're calling fct(S), without handling the return value, then you'll lose that new value ("titi").