What are the implications of enabling trace flag 1222 - write deadlock information to the log?
sql-server,database-deadlocks,dbcc
Based on many things I have heard around I currently have the following opinion: There is very little overhead in enabling the trace flag unless you’re experiencing lots of deadlocks, which would cause a large amount of deadlock graphs to be written to the error log. However, it doesn’t sound...
Database deadlock by select statement
mysql,database,deadlock,database-deadlocks
With the InnoDB storage engine (the default), reads are non-blocking - so two selects cannot block each other. InnoDB is a versioning engine using MVCC (multi-version concurrency control) meaning that a transaction (A) will take a copy of the records of interest at a moment in time - if it...
Best way to deal with deadlock in SqlServer?
sql-server,tsql,sql-server-2008-r2,deadlock,database-deadlocks
It is not common for a read to cause a deadlock but it can happen It will only happen if it conflicts with an update transaction Look at all the read and updates I know I am going to get lambasted for this but try the reader command with (no...
Deadlock when updating `djcelery_periodictask` table
celery,django-celery,database-deadlocks,celerybeat
My problem was that I had all of my workers started with -B parameter which turned each worker in a periodic task scheduler: -B, --beat Also run the celery beat periodic task scheduler. Please note that there must only be one instance of this service. As a result, the scheduled...
T-SQL Deadlocks when I query SELECT in autocommit off mode in SQL Server Management Studio
sql-server,tsql,deadlock,database-deadlocks
See this Technet article on deadlocking - it uses the case of a single table with only 2 rows to discuss how a deadlock can be created. Once you get into real-world systems with far more tables, connections and code-paths predicting and preventing deadlocks becomes much harder. If you are...
What are 'best practices' for dealing with transient database errors in a highly concurrent Rails system?
ruby-on-rails,activerecord,database-deadlocks
The fix, for me, was a better index. The update in question was in a query with a join, and existing indexes were not sufficient for MySQL to join and search efficiently. Adding the appropriate index completely removed the deadlock issue even in tests with unreasonably concurrent loads....
MySQL Deadlock On 2 Updates
mysql,innodb,database-deadlocks
From MySQL Documentation - 14.2.7.9 How to Cope with Deadlocks (highlight added): When modifying multiple tables within a transaction, or different sets of rows in the same table, do those operations in a consistent order each time. Then transactions form well-defined queues and do not deadlock. For example, organize database...
Oracle Deadlock while updating
oracle,sql-update,database-deadlocks
You could do it in two stages; query the table with FOR UPDATE NOWAIT, which will throw an exception if the row is already locked, and then do the update (and commit) if it doesn't error: SELECT * FROM person WHERE person_id = 1234567 FOR UPDATE NOWAIT; UPDATE person SET...
How to add new columns to over 10 GB innodb mysql table without affecting production performance?
mysql,innodb,database-deadlocks
I don't see what went wrong. Suggest you file a bug at bugs.mysql.com. Meanwhile, you could use pt-online-schema-change to do the change with virtually no downtime....
Postgres 9.3: Sharelock issue with simple INSERT
It looks like you're in this situation: The table to INSERT into has a primary key (or unique index(es) of any sort). Several INSERTs into that table are performed within one transaction (as opposed to committing immediately after each one) The rows to insert come in random order (with regard...
How to avoid Deadlock in this scenario?
mysql,database,database-deadlocks
First I have some nasty things to say, then I will get to a possible solution. "Don't queue it, just do it." -- MySQL does not make a good queuing engine. Do add BEGIN...COMMIT (as already mentioned). And the BEGIN...COMMIT needs to be around the other code, too. Do add...
MSSQL Deadlock when update withc (updlock)
sql-server,tsql,sql-update,database-deadlocks
You are processing multiple rows per transaction, right? This should not deadlock for one row You might get double-inserts, though, which is a bug. Two sessions might conclude that there is no row and then both will insert. There are two ways to make this safe: Issue the select WITH...
Deadlock In Sql Server 2012 With Merge
This sounds like a hard to solve deadlock. Usually, one would solve this by ensuring a consistent lock order and increasing the lock mode to something above S. It is unclear how this would be done here. Suggestions: Can you tolerate the (rare) background update to U-lock the table? That...