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Displaying posts with tag: transactions (reset)

Checking transactions in MySQL
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I'd been doing some stress testing of my mysql application today, and I was hitting some weird cases. Several transactions were deadlocking - this was expected - but the number of records that got inserted into my table was more than the number that I expected after subtracting errors.

My test was fairly simple:

  1. Fork 15 processes
  2. Insert and update 100 records in each process, running each INSERT/UPDATE pair inside one transaction
  3. ROLLBACK on error

Either the INSERT or the UPDATE was expected to fail due to deadlock, and the whole transaction should have rolled back leaving no record in …

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Fasten your seatbelts ...
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... or how to safely run data manipulation statements in your database.Reading posts on Devshed's forums I sometime notice people doing maintenance work on their data without any safety net apart from occasional ages old backups ;-).Anyway I think there's no need for a restore if you just issued the wrong update query, I mean, transactions are here for this, it's just a matter of educating people

Making PBXT Fully Durable
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Until now PBXT has been ACId (with a lower-case d). This is soon to change as I have had some weeks to work on a fully durable version of the transactional engine (

My first concern in making PBXT fully durable was to what extent I would have to abandon the original "write-once" design. While there are a number of ways to implement durability, the only method used by databases (as far as I know) is the write-ahead log.

The obvious advantage of this method is that all changes can be flushed at once. However, this requires that all data be written …

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MySQL Toolkit version 989 released
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MySQL Parallel Dump can now dump a single table simultaneously into many files of a user-specifed size. This not only helps speed dumps, but it paves the way for much more efficient parallel restores. Read on for the details.

Version 1.5.2 of the innotop MySQL monitor released
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This release is part of the unstable 1.5 branch. Its features will ultimately go into the stable 1.6 branch. You can download it from the innotop-devel package.

The major change is I've ripped out the W (Lock Waits) mode and enabled innotop to discover not only what a transaction is waiting for, but what it holds too. The new mode that replaces W is L (Locks). My last article goes into more detail on this.

How to debug InnoDB lock waits
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This article shows you how to use a little-known InnoDB feature to find out what is holding the lock for which an InnoDB transaction is waiting. I then show you how to use an undocumented feature to make this even easier with innotop.

Archive strategies for OLTP servers, Part 3
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In the first two articles in this series, I discussed archiving basics, relationships and dependencies, and specific archiving techniques for online transaction processing (OLTP) database servers. This article covers how to move the data from the OLTP source to the archive destination, what the archive destination might look like, and how to un-archive data. If you can un-archive easily and reliably, a whole new world of possibilities opens up.

Archive strategies for OLTP servers, Part 2
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In the first article in this series on archiving strategies for online transaction processing (OLTP) database servers, I covered some basics: why to archive, and what to consider when gathering requirements for the archived data itself. This article is more technical. I want to help you understand how to choose which rows are archivable, and how to deal with complex data relationships and dependencies. In that context, I'll also discuss a few concrete archiving strategies, their strengths and shortcomings, and how they can satisfy your requirements, especially requirements for data consistency, which as you will see is one of the most difficult problems in archiving.

10 Newer Entries Showing entries 31 to 38

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