I have some piece of code in my Website which adds the details into tables. Now I want that if some error occurs the previously entered data should be removed. How can I implement it with the help of transactions??
We need more details such as what database you are using and so forth. Basically you do this:
Create a transaction
Do some work in the context of that transaction
Do some more work in the context of that transaction
...
If an exception occurred, rollback the transaction, else commit.
Related
I am starting to dabble in tSQLt and a few times have accidentally hit F5 and executed my test proc directly instead of through tSQLt.RunAll, which hoses my entire database. Is there any simple way to roll back that accidental execution instead of restoring my entire database from backup?
The full error is [myDClass].[test myTest] failed: (Error) There is already an object named 'pMyProc_SpyProcedureLog' in the database.[16,6]{,1} (There was also a ROLLBACK ERROR --> The current transaction cannot be committed and cannot be rolled back to a savepoint. Roll back the entire transaction.{tSQLt.Private_RunTest,162})
I checked DBCC OPENTRAN but there aren't actually any transactions listed.
On the linux server, where our web app runs, we also have a small app that uses
sqlite (it is written in c).
For performing database actions we use the following commands:
sqlite3_prepare_v2
sqlite3_bind_text or sqlite3_bind_int
sqlite3_step
sqlite3_finalize
Every now and then there was a concurrency situation and I got the following error:
database is locked
So I thought: "This happens when one process writes a certain record and the
other one is trying to read exactly the same record."
So after every step-command, where this collision could be, I checked for this error. When it happended, I waited a few milliseconds and the tried again.
But the sqlite error "database is locked" still occurred.
So I changed every step command and the code lines after it. Somehow I thought that this "database is locked" error could only occur with the step command.
But the error kept coming.
My question is now:
Do I have to check after any sqlite3 command for "error_code ==5" (database is locked)?
Thanks alot in advance
If you're receiving error code 5 (busy) you can limit this by using an immediate transaction. If you're able to begin an immediate transaction, SQLite guarantees that you won't receive a busy error until you commit.
Also note that SQLite doesn't have row-level locking. The entire database is locked. Using a WAL journal, you can one writer and multiple readers. With other journaling methods, you can have either one writer, or multiple readers, but not both simultaneously.
SQLite Documentation on 'SQLITE_BUSY'
While saving data in Pega PRPC using activity with Obj-save method, I got following error message:
pyCommitError: A commit cannot be performed because a deferred save of instance ANDY-FW-ANDYCARRENTALFW-DATA-CARINFO L3 failed: code: SQLState: Message:
Can anyone share some idea on how to fix this issue?
Andy
This message could come when we have a field which has a less field length specified in DB and we are trying to insert bigger string in the field.
There could be other reasons as well.See Tracer.
Deferred save of instance usually fails due to locked instance which you are trying to commit. Or the record you are trying to commit is stale (someone else committed before your commit)
Ideally, this behavior can be observed because of the lock on the work object not being held while you are trying to save the object. Make sure you acquire the lock before updating and save.
Additionally please check if privilege is given to the operator.
I am trying to confirm how the actual ADODB.Connection.Errors collection should actually work.
My interpretation at the moment is that the connection will hold all the errors for the all the procedures that have been executed on that connection.
So I should be able to say
on error resume next
... code goes here ... 2 or more command objects execute procedures against the database on the same connection
if con.Errors <> 0 then
loop through all the Errors objects (1 for each procedure that would've been executed on the connection)
end if
However I have implemented that basic structure and I only get the one error description? So I am looking for someone to confirm that is the case. Does the Errors collection hold more than one error for more than one procedure? Or is if multiple errors occurred for one procedure?
I can't seem to find any documentation that would indicate exactly what would happen in this case.
Thanks,
from Errors Collection (ADO) - MSDN:
Any operation involving ADO objects can generate one or more provider
errors. As each error occurs, one or more Error objects can be placed
in the Errors collection of the Connection object. When another ADO
operation generates an error, the Errors collection is cleared, and
the new set of Error objects can be placed in the Errors collection.
So, to catch all errors, seems to be need to check the collection after each possible error.
I'm Altering multiple sqlite tables with SQL script by calling ExecuteNonQuery. I want to do this operation in transaction and want to roll it back when anything fails.
I looked at BEGIN TRANSACTION and its clear that I have to call ROLLBACK TRANSACTION when anything goes wrong. But I don't know how could TRY...CATCH (Transact-SQL) kind of thing here.
NOTE: Whole of Sql Script file (which contains many other statements apart from these few statements which needs to be fired in one transaction) is read by .ReadToEnd() and then executed in one go as of now. I want to handle this in sql script file itself and don't want to change the code.
Please take a look at SQLite on conflict clause
Start with BEGIN TRANSACTION
You have to add ON CONFLICT ROLLBACK on your actions
And COMMIT TRANSACTION at the end ;-)