We have been observing a deadlock on 2 sessions, one which is executing Database ; and the other session has revoke statements. Can this be possible?
Thanks,
Piyush
Related
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'
I'm trying to debug a deadlock on Redshift:
SQL Execution failed ... deadlock detected
DETAIL: Process 7679 waits for AccessExclusiveLock on relation 307602 of database 108260; blocked by process 7706.
Process 7706 waits for AccessShareLock on relation 307569 of database 108260; blocked by process 7679.
Is there a sql query to get a description for process ids 7679 and 7706?
select * from stl_query where pid=XXX
This will give you the query txt which will help you identify your query.
You can also query stv_locks to check is there are any current updates in the database, and str_tr_conflict will display all the lock conflict on the table.
For a particular requirement, I will have to iterate through a list of 50000 records and insert them into database. The requirement is that if any one of the 50000 records fail, all the other records should be rollback. And hence we did not involve any commit in the processing. But this resulted in the following error:
[2/1/16 14:01:47:939 CST] 000000be SystemOut O ERROR
org.springframework.jdbc.UncategorizedSQLException:
PreparedStatementCallback; uncategorized SQLException for SQL [INSERT
INTO ...) VALUES (...)]; SQL state [null]; error code [0]; Current
thread has not commited in more than [120] seconds and may incur
unwanted blocking locks. Please refactor code to commit more
frequently.
Now, when we implemented batching - We are using PreparedStatement.executeBatch() method to insert data in batches of 100, the above error doesn't arise. The autoCommit is set to true by default for the batching, so a commit happens after every batch execution.
Could anyone suggest how we can handle the rollback mechanism in the above case. If 50th batch execution fails, then we want all the previous 49 batch executions to be reverted. We are using Spring Data/JDBC, Oracle 11g database, WebSphere application server. I have read somewhere that the above 120 seconds timeout for commit can also be configured in the JTA settings of WebSphere. Is it so? Please suggest any alternatives or other possible solutions.
Thank you in advance.
You must set autocommit to false and only commit at the end if all your batches executed successfully.
Im getting a time out expired.
The timeout period elapsed prior to completion of the operation.
If I execute the same query in SQL server management its getting executed but trying to execute the query through the program does not succeed.
Where could I have gone wrong?
The query is very simple and its throwing exception.
The time out set is 90 sec.
Select isnull(max(voucherid),0)+1 from XXX
dbmanager.executequery(con,"uspXXX",parameter);
Rebuild your statistics and/or indexes on that table.
See this answer.
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 ;-)