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Displaying posts with tag: debugging (reset)

GDB Tips: Inspecting MySQL Plugin Variables in Core File
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Recently I had a need to determine the session value of a MySQL plugin variable in a core file.  Here I use the word plugin variable to refer to MySQL system variables provided by plugins.  While this is not a very difficult task, it is not as straight forward as printing a global variable. It took some time to figure out the layout of the plugin variables and get the needed information. This short article is to share this gdb tip with other interested MySQL developers and support engineers.

In this article, let us inspect the …

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#DBHangOps 10/02/13 — MySQL Utilities, Resource Management, and more!
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Thanks to everyone who came. Definitely check out the recording below!

Heyo everybody!

Coming up this Wednesday, October 2nd, 2013 at 12:00pm pacific (19:00 GMT) is another exciting #DBHangOps. Join the google hangout to discuss:

  • MySQL Utilities from Chuck Bell!
  • How do you constrain over-consumption of resources by competing applications?
  • Network vs. Local storage for MySQL
    • How do you use this for HA? Do you use DRBD or floating VIPs?
  • Secure connections to MySQL (using SSL) (requested …

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#DBHangOps 7/24/13 — Innobackupex, schema migrations, and more!
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And all set. Check out the recording:

Hello everybody!

Coming up this Wednesday, July 23rd, 2013 at 12:00pm pacific (19:00 GMT) join in to hear:

  • Brandon Johnson from Mozilla talk about an issue he recently worked through with XtraBackup and the process he took to identify and resolve the issues.

And also take part in discussion around:

  • How do you apply production schema changes?
    • Do you use pt-online-schema-change?
      • Issues to watch out for
    • Just run …

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The network is reliable
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A fascinating post-mortem on high profile network failures:

This post is meant as a reference point–to illustrate that, according to a wide range of accounts, partitions occur in many real-world environments. Processes, servers, NICs, switches, local and wide area networks can all fail, and the resulting economic consequences are real. Network outages can suddenly arise in systems that are stable for months at a time, during routine upgrades, or as a result of emergency maintenance. The consequences of these outages range from increased latency and temporary unavailability to …

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#DBHangOps 3/27/13!
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Hi everyone!

Here’s a video of this week’s #DBHangOps:

March 27th at 12:00pm PDT (19:00 GMT) is when the next #DBHangOps is gonna go down. Check out the twitter search and hop on the google hangout to contribute some discussion! This week’s topics are:

  • MySQL and puppet
    • Sheeri Cabral shared a pastebin of a puppet manifest used at Mozilla: http://scabral.pastebin.mozilla.org/2251358
  • MySQL “Gotchas” (round 2)

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MySQL Debugging Methods Overview
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Introduction
Debugging SQL code is a very important task these days. Unfortunately not all database servers support this feature. And MySQL is one of such servers. In spite of its wide feature set, debugging is not implemented in it. So the problem is that MySQL provides no API functionalities for code debugging. But the necessity to debug SQL code does not disappear and becomes more and more important each year. Some companies that develop tools to access data of MySQL server databases create their own debuggers that solve this problem to some extent.

Types of Debuggers


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MySQL Debugging Methods Overview
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The article describes the ways to debug MySQL stored routines with a GUI tool.

Tale of a bug
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This is a tale of the bug lp:798213. The bug report has the initial report, and a summary of the real problem obtained after detailed analysis, but it does not describe the processes of getting from the former to the latter. I thought it would be interesting to document this, as the analysis of this bug was rather tricky and contains several good lessons.

Background

The bug first manifested itself as a sporadic failure in one of our random query generator tests for replication. We run this test after all MariaDB pushes in our …

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MySQL stored procedure debugging, can I sue for going insane?
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Lets paint the picture:

Scenario part 1 : Migrating a couple thousand stored procedures from database technology X to mysql
Scenario part 2 : Legacy system where the people who wrote it left a long time ago
Scenario part 3 : Developers sure can get real creative and invent all kinds of ways to get data (eg: having a stored proc which formulates a big query using concat after going through a bunch of conditions (fair enough), BUT the parts making up the different queries are stored in a table on a database rather than within the stored proc itself) … talk about KIS – Keep it simple!!
Scenario …


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Debugging memory leaks in plugins with Valgrind
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I had an interesting IRC discussion the other day with Monty Taylor about what turned out to be a limitation in Valgrind with respect to debugging memory leaks in dynamically loaded plugins.

Monty Taylor's original problem was with Drizzle, but as it turns out, it is common to all of the MySQL-derived code bases. When there is a memory leak from an allocation in a dynamically loaded plugin, Valgrind will detect the leak, but the part of the stack trace that is within the plugin shows up as an unhelpful three question marks "???":

==1287== 400 bytes in 4 blocks …
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Showing entries 1 to 10 of 25 10 Older Entries

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