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1answer
167 views

timestamp based concurrency

I am wondering if someone could help me out with a question I have about time stamp based concurrency. I found the following practice problem on a website It basically asks which of the following ...
0
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1answer
199 views

Why we use low numbers for concurrent in MySQL benchmarks or HTTP_LOAD? [closed]

I've seen so many times that we use numbers like 5,6 or 10 at most. What is this concurrency? Doesn't it refer to number of simultaneous users in bench? EDIT I'm not talking about any specific ...
1
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1answer
485 views

Which Optimistic Concurrency Control method will work out best in the long run?

These are the options I've thought of: DotNet Dave: UPDATE mytable set f1=newval where id=666 and f1 := f1ValueFromSelect Charlie Checksum: UPDATE mytable set f1=newval where id=666 and ...
3
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1answer
1k views

Concurrency with Select-conditional Insert/Update/Delete - PostgreSQL

I have an intervals table which stores a start date and an end date for variables variable_id (four columns : id, start, end, variable_id). Clients compute new intervals for one variable and store ...
4
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2answers
8k views

Using multiple cores for single MySQL queries on Debian

I am running a MySQL server for tests on a VM (VMWare) with Debian as guest OS. The guest has four emulated CPU cores, so I set thread_concurrency to four. I am doing expensive joins on large tables, ...
8
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3answers
2k views

Insert if not exists, concurrently

I am having concurrency issues with my inserts in a stored procedure. The relevant part of the procedure is this: select @_id = Id from table1 where othervalue = @_othervalue IF( @_id IS NULL) BEGIN ...
6
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4answers
483 views

Resources for understanding SQL Server locking and concurrency?

As demonstrated by a recent question of mine locking and concurrency are HARD. Can you suggest any good resources for intermediate-to-advanced SQL professionals to do a thorough study on these that ...
16
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3answers
3k 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, ...
11
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1answer
267 views

Highly Concurrent Storage System

Imagine your requirement is that you have 3 huge tables (structured data) with say 30 billion rows in each (total size of 4TB) and your many concurrent users (which are parallel os threads on remote ...
3
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1answer
5k views

Oracle 11g hunting down the deadlock, maybe foreign key?

I am trying to understand why a deadlock occurs in my database. The trace tells me that two updates on the same table are locking. In table is the first table to be written to in an transaction, only ...
1
vote
1answer
118 views

Can a Database request automatically remove itself from the queue after a delay?

I'm using table locking in my Oracle database. I have a small program with a function that locks my table, does some things and unlocks it again. If many instances are run and requests are made ...
4
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3answers
5k views

Concurrent MySQL updates hang with InnoDB (on Amazon RDS)

I'm running into a problem where multiple MySQL updates being performed at the same time will lock up and takes several minutes to finish. I'm using InnoDB, so I'm confused as to why this could be ...
4
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2answers
2k views

Concurrent Transactions vs Simultaneous Transactions

Chapter 6 of David Kroenke's Database Concepts: Database Administration Is my understanding correct that in a database, simultaneous transactions don't really happen. Instead, it is a concurrent ...
3
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2answers
1k views

Concurrently update with limit mysql

I want to know if concurrently UPDATE .... LIMIT N will not overlap with more than one client querying the db. After UPDATE ... LIMIT N the client will make a SELECT with some client_id assigned. I ...
0
votes
1answer
335 views

How could I handle heavy load and consistency for product inventory in online retailers? [closed]

I have posted that question on Stackoverflow and they suggest me to repost my question here, as it would more likely to get help from a DB community (regarding this issue). Hope you guys don't mind. ...
4
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2answers
200 views

Concurrency question?

I have a MySql (5.5) database with a MS Access frontend. If two users are viewing the same record at the same time how can I make each user aware of each other? For example how would I go about ...
12
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2answers
2k views

Can I create index on a table in a MySQL database while in use

And if I can, any reason (performance/stability) why I shouldn't?
23
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4answers
1k views

How do you test for race conditions in a database?

I try to write database code to make sure that it's not subject to race conditions, to make sure that I've locked the correct rows or tables. But I often wonder: Is my code correct? Is it possible to ...