database-deadlocks | 易学教程

Database Deadlock in SELECT FOR UPDATE

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问题 I'm getting deadlock intermittently in my application. My application has 1 table e.g EMPLOYEE (ID (PK), NAME, SAL) and there are 2 sessions. Session 1: SELECT ID, NAME, SAL FROM EMPLOYEE WHERE SAL = (SELECT MIN(SAL) FROM EMPLOYEE) FOR UPDATE Let say the query return EMPLOYEE ROW having ID=2 then application does some processing like rs.updateInt(ID_SAL, 10); Session 2: (for other business logic) SELECT ID, NAME, SAL FROM EMPLOYEE WHERE ID=2 FOR UPDATE. So, in the application both sessions

MySQL 5.6 deadlock for locking the same rows twice?

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I am seeing a deadlock with MySQL 5.6 because of what seems like trying to lock the same row/s twice. From the snippet below, rows where id = (11, 12, 13, 14, 15) already have a lock. And when another transaction tried to acquire a lock on these, MySQL failed the transaction detecting a deadlock. Is my reading of this correct? If so, is there anything in MySQL 5.6 to get over this? FWIW, the same code in 5.5 worked just fine (for several hundreds of iterations). ------------------------ LATEST DETECTED DEADLOCK ------------------------ 2013-07-25 11:46:05 13a515000 *** (1) TRANSACTION:

How do I identify a deadlock in SQL Azure?

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I have a Windows Azure role that consists of two instances. Once in a while a transaction will fail with an SqlException with the following text Transaction (Process ID N) was deadlocked on lock resources with another process and has been chosen as the deadlock victim. Rerun the transaction. Now I've Googled for a while and read this post about identifying deadlocks using SQL Server logs. The problem is... How do I do it in SQL Azure? What tools do I use to access the internals of SQL Azure and getting enough data? Monitoring of SQL Azure is more limited than SQL Server, but the tools are

Best Isolation Level to avoid deadlocks using an UPDATE sentence in Sql Server 2005

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i need execute un update statement over an sql server table, this table is used by another process at the same time. because that sometimes deadlocks ocurs. wich Isolation Level do you recomend to avoid or minimize this deadlocks? READ UNCOMMITTED But that allows the process to read the data before a transaction has committed, what is known as a dirty read. Further Reading You may prefer to turn on row versioning, the update creates a new version of the row and any other select statements use the old version until this one has committed. To do this turn on READ_COMMITTED_SNAPSHOT mode. There

How to do a safe “SELECT FOR UPDATE” with a WHERE condition over multiple tables on a DB2?

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问题 Problem On a DB2 (version 9.5) the SQL statement SELECT o.Id FROM Table1 o, Table2 x WHERE [...] FOR UPDATE WITH RR gives me the error message SQLSTATE=42829 (The FOR UPDATE clause is not allowed because the table specified by the cursor cannot be modified). Additional info I need to specify WITH RR , because I'm running on isolation level READ_COMMITTED , but I need my query to block while there is another process running the same query. Solution so far... If I instead query like this:

Can two “SELECT FOR UPDATE” statements on the same table cause a deadlock?

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问题 Suppose that two simultaneous transactions execute the following queries on a Postgresql DB: Transaction A: SELECT * FROM mytable WHERE id IN (1, 2, 3, 4) FOR UPDATE Transaction B: SELECT * FROM mytable WHERE id IN (6, 3, 2, 1) FOR UPDATE Is it possible for a deadlock to occur due to Postgresql acquiring row locks in an inconsistent order? E.g. if Postgresql were to acquire row locks in the order the ids are given in this example, then there is a potential for deadlock. Or is Postgresql

Deadlock error in INSERT statement

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问题 We've got a web-based application. There are time-bound database operations (INSERTs and UPDATEs) in the application which take more time to complete, hence this particular flow has been changed into a Java Thread so it will not wait (block) for the complete database operation to be completed. My problem is, if more than 1 user comes across this particular flow, I'm facing the following error thrown by PostgreSQL: org.postgresql.util.PSQLException: ERROR: deadlock detected Detail: Process

MySQL Select… for update with index has concurrency issue

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This is a follow up on my previous question (you can skip it as I explain in this post the issue): MySQL InnoDB SELECT...LIMIT 1 FOR UPDATE Vs UPDATE ... LIMIT 1 Environment: JSF 2.1 on Glassfish JPA 2.0 EclipseLink and JTA MySQL 5.5 InnoDB engine I have a table: CREATE TABLE v_ext ( v_id INT NOT NULL AUTO_INCREMENT, product_id INT NOT NULL, code VARCHAR(20), username VARCHAR(30), PRIMARY KEY (v_id) ) ENGINE=InnoDB DEFAULT CHARSET=UTF8; It is populated with 20,000 records like this one ( product_id is 54 for all records, code is randomly generated and unique, username is set to NULL): v_id

how to avoid deadlocks with neo4j

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I just learnt that when I create a relationship between 2 nodes in neo4j, both of them are locked ( http://docs.neo4j.org/chunked/stable/transactions-locking.html ). However, in our project, we have elements that we can instanciate and we finnaly have two nodes in the graph linked by a "INSTANCE_OF" relationship. For exemple if I instanciate element B, I have a new element B1. They are stored in the graph like B<-INSTANCE_OF-B1. My problem is that many users can instanciate element B on same time and it result in deadlocks. How can I avoid these deadlocks please ? I don't need to write

Postgres deadlocks on concurrent upserts

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We have an application which reads from a data stream and upserts that information into a database. The data is changes which occur on Google Drive which means that many events which impact the same objects can occur very close to each other. We're running into deadlocks when upserting this information into the database, here is what comes out in the log. I have reconstructed and sanitised the query for readability: ERROR: deadlock detected DETAIL: Process 10586 waits for ShareLock on transaction 166892743; blocked by process 10597. Process 10597 waits for ShareLock on transaction 166892741;