Can anybody please tell me how to handle a transaction rollback in squeryl explicitly?
And also how can we add or remove columns in squeryl dynamically?
Thanx...
Just to elaborate a bit on the response from #didierd. There is one Session/Connection bound to each transaction. You can access the current Session, and thereby the Connection with code like:
Session.currentSession.connection
Or, if you're not sure if you're within a transaction
Session.currentSessionOption map {_.connection}
If you do roll back the transaction this way it will be your responsibility to start a new one or make sure there is no further use of the connection, so use with care.
You have an access to the JDBC's java.sql.Connection (connection in Session), so if you really cannot use transaction / inTransaction, you can call rollback there.
With access to the connection, you can also execute arbitrary SQL requests and so change the database schema, but be mindful that your squeryl-using code has a static, compile time known schema.
Related
As far as I can tell, the COPY command in Postgres supports transactions, but I don't see a way to specify a transaction with NpgsqlConnection.BeginBinaryImport. Is it not supported?
BeginBinaryImport implicitly participates in a transaction started before it. So just do NpgsqlConnection.BeginTransaction first, and then call BeginBinaryImport.
I had added the Extended event to track sql calls which is slowing down my system leading to Timeout exceptions and other
CREATE EVENT SESSION [longrunning_statements] ON SERVER
ADD EVENT sqlserver.sql_statement_completed(
WHERE ([duration]>(2000000) AND [database_id]=(9)))
ADD TARGET package0.event_file(SET filename=N'c:\capture\xe_longrunning_statement.xel',metadatafile=N'c:\capture\xe_longrunning_statement.xem')
WITH (MAX_MEMORY=4096 KB,EVENT_RETENTION_MODE=ALLOW_SINGLE_EVENT_LOSS,MAX_DISPATCH_LATENCY=30 SECONDS,MAX_EVENT_SIZE=0 KB,MEMORY_PARTITION_MODE=NONE,TRACK_CAUSALITY=OFF,STARTUP_STATE=OFF)
GO
But i noticed it does not register sql server updates/read queries/procedures calls from Entity Framework but only logged my sql queries run using SSMS.
Any ideas are appreciated
UPDATE:
I use EF6.1 which used i think batches to save data.
Instead of trying to capture sqlserver.sql_statement_completed I would capture sqlserver.sql_batch_completed and sqlserver.rpc_completed for application/API issued queries/stored procedures.
If that does not work then removing the filters(or at least the duration filter (as Andrey is suggesting in the comments) would probably give us more insight on why the queries are not being captured.
I have a classic spray+slick http server which is my database access layer, and I'd like to be able to have an healthcheck route to ensure my server is still able to reach my DB.
I could do it by doing a generic sql query, but I was wondering if there was a better way to just check the connection is alive and usable without actually adding load on the database (or at least the minimum possible load).
So pretty much :
val db = Database.forConfig("app.mydb")
[...]
db.???? // Do the check here
Why do you want to avoid executing a query against the database?
I think the best health check is to actually use the database as your application would (actually connecting and running a query). With that in mind, you can perform a SELECT 1 against your DB, and verify that it responds accordingly.
I'm trying to understand how a java (client) application that communicates, through JDBC, with a pgSQL database (server) can "catch" the result produced by a query that will be fired (using a trigger) whenever a record is inserted into a table.
So, to clarify, via JDBC I install a trigger procedure prepared to execute a query whenever a record is inserted into a given database table, and from this query's execution will result an output (wrapped in a resultSet, I suppose). And my problem is that I have no idea how the client will be aware of those results, that are asynchronously produced.
I wonder if JDBC supports any "callback" mechanism able to catch the results produced by a query that is fired through a trigger procedure under the "INSERT INTO table" condition. And if there is no such "callback" mechanism, what is the best approach to achieve this result?
Thank you in advance :)
Triggers can't return a resultset.
There's no way to send such a result to the JDBC driver.
There are a few dirty hacks you can use to get results from a trigger to the client, but they're all exactly that. Things like:
DECLARE a cursor for the resultset, then send the cursor name as a NOTIFY payload, so the app can FETCH ALL FROM <cursorname>;
Create a TEMPORARY table and report the name via NOTIFY
It is more typical to append anything the trigger needs to communicate to the app to a table that exists for that purpose and have the app SELECT from it after the operation that fired the trigger ran.
In most cases if you need to do this, you're probably using a trigger where a regular function is a better fit.
HI,
Iam trying to insert batch of records at a time when any of the record fails to insert i need to trap that record and log that to my failed record maintanance table and then the insert should continue. Kindly help on how to do this.
If using a Spring or EJB container there is a simple trick which works very well : provide a LogService witn a logWarning(String message) method. The method must be annotated/configured with the REQUIRES_NEW transaction setting.
If not then you'll have to simulate it using API calls. Open a different connection for the logging, when you enter the method begin the transaction, before leaving commit the transaction.
When not using transactions for the insert, there is actually nothing special you need to do, as by default most database run in autocommit and commit after every statement.