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5
votes
4answers
497 views
MySQL InnoDB locks primary key on delete even in READ COMMITTED
Preface
Our application runs several threads that execute DELETE queries in parallel. The queries affect isolated data, i.e. there should be no possibility that concurrent DELETE occurs on the same ...
3
votes
2answers
86 views
Does SQL Server place shared locks on scanned records when using REPEATABLE READ
Assume a SQLCmd session which is using transaction isolation level REPEATABLE READ.
In this session I start a transaction and execute an UPDATE statement with a WHERE clause on a non indexed column. ...
13
votes
3answers
1k views
Managing concurrency when using SELECT-UPDATE pattern
Let's say you have the following code (please ignore that it's awful):
BEGIN TRAN;
DECLARE @id int
SELECT @id = id + 1 FROM TableA;
UPDATE TableA SET id = @id; --TableA must have only one row, ...
5
votes
3answers
1k views
SQL Server - what isolation level for non-blocking select statements?
I have a long running transaction (called, say, T1) that performs some deletes, updates and inserts on a table in SQL Server 2008 R2. At the same time, another process periodically runs select ...
