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Questions tagged [read-committed]

29 questions
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Read Committed vs Read Uncommited if both transaction do not rollback

I am trying to understand read committed and read uncommitted isolation levels. I know that theoreticay read uncommitted allows dirty reads and read committed doesn't, but I still can't really understand. Considering Figure above, if none of the…
user1264
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Why I shouldn't use "Repeatable Read" with locking reading (select..for update)"?

In the Mysql Document: "https://dev.mysql.com/doc/refman/5.7/en/innodb-deadlocks-handling.html" It mentioned: "If you use locking reads (SELECT ... FOR UPDATE or SELECT ... LOCK IN SHARE MODE), try using a lower isolation level such as READ…
Box Very
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READ COMMITTED database isolation level in oracle

I'm working on a web app connected to oracle. We have a table in oracle with a column "activated". Only one row can have this column set to 1 at any one time. To enforce this, we have been using SERIALIZED isolation level in Java, however we are…
Ben
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Postgres read commited doesn't re read updated row

Good day. I was playing with READ COMMITTED isolation level in postgres and found strange behavior which doesn't follow official documentation. Let's say I have a table account(id int,name text,amount int) and two rows. test> select * from account;…
Almas Abdrazak
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1 answer

InnoDB x-locks in READ COMMITTED isolation level

From MySQL glossary: READ COMMITTED When a transaction with this isolation level performs UPDATE ... WHERE or DELETE ... WHERE operations, other transactions might have to wait. The transaction can perform SELECT ... FOR UPDATE, and LOCK IN SHARE…
Croco
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Locking a newly created, uncommitted row in two concurrent READ COMMITTED database transactions

If I have two READ COMMITTED PostgreSQL database transactions that both create a new row with the same primary key and then lock this row, is it possible to acquire both locks successfully at the same time? My instinct is yes since these new rows…
Kevin King
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Can Lost Update happen in read committed isolation level in PostgreSQL?

I have a query like below in PostgreSQL: UPDATE queue SET queue.status = 'PROCESSING' WHERE queue.status = 'WAITING' AND queue.id = (SELECT id FROM queue WHERE STATUS = 'WAITING' LIMIT 1 ) RETURNING queue.id and…
pmoubed
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Can I get ORA-08177 if there's only one connection to the database?

I've been tasked with running the unit tests on a storm backend for oracle so that we can see if the backend is of sufficient quality to use in production. One problem that I'm running into is that I'm getting ORA-08177 (can't serialize access for…
Jason Baker
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How does InnoDB take and retain record locks on READ COMMITTED LEVEL

mysql-refman-5.7, 14.7.2.1 Transaction Isolation Levels, says: Under READ COMMITTED, "For UPDATE or DELETE statements, InnoDB holds locks only for rows that it updates or deletes. Record locks for nonmatching rows are released after MySQL has…
Jack Ma
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Understanding InnoDB X-Lock with REPEATABLE_READ and READ_COMMITED isolation level

I have two mysql(AWS Aurora) db tables: -------------------------------- | Table:deparment | -------------------------------- -------------------------------- | id | dept_name | -------------------------------- | d1 …
Rajdip
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Does SELECT prevent returned rows from getting deleted?

Say I have: T1: SELECT id FROM x WHERE timestamp < y (returns id = [1, 2, 3]) T2: DELETE FROM x WHERE id = 1 T1: SELECT timestamp, value FROM x WHERE id = 1 with READ-COMMITTED isolation. Does step 3 run the risk of returning an empty result, or…
Gili
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Alternative ways to handle cuncurrency in a cinema bookin system

My group and i have made a cinema booking system for a school project where the subject was cuncurrency control. It is made with c# and entity framework in an n-tier arcitecture where the presentationtier consisted of an mvc project. We chose to…
Michael Kirkegaard
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Why is it a "lost update" in the Read Committed Transactions example of Oracle documentation?

In the book "Oracle Database Concepts", Oracle gives an example to explain Read Committed Isolation Level. In the example, transaction 1 updates row 1, then transaction 2 updates the same row before transaction 1 commits. So, transaction 2 waits…
Fang Zhen
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Does it possible use read only committed in Teradata?

I have found that Teradata uses: READ_ISOLATION_LEVEL= ACCESS|READ|WRITE How it correspond to usual read commited/dirty in usual databases? Thanks.
user710818
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MySQL REPEATABLE-READ Workbench transaction level not set

We have set the following in the my.ini file [mysqld] transaction-isolation = READ-COMMITTED We assume this setting will be the default for all user sessions. When logging in using PHPMyAdmin the tx_isolation is set correctly and works as expected.…
user2374309
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