Tag - Debugging

Why Optimization derived_merge can Break Your Queries

MySQL optimizer bugs

Lately, I worked on several queries which started returning wrong results after upgrading MySQL Server to version 5.7 The reason for the failure was derived merge optimization which is one of the default
optimizer_switch  options. Issues were solved, though at the price of performance, when we turned it
OFF . But, more importantly, we could […]

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Percona Live Europe Featured Talks: Debugging with Logs (and Other Events) Featuring Charity Majors

Percona Live Europe 2017

Welcome to another post in our series of interview blogs for the upcoming Percona Live Europe 2017 in Dublin. This series highlights a number of talks that will be at the conference and gives a short preview of what attendees can expect to learn from the presenter.
This blog post is with Charity Majors, CEO/Cofounder […]

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MySQL QA Episode 6: Analyzing and Filtering

Welcome to MySQL QA Episode #6!
Today we will look into analyzing and filtering our QA run. We’ll use tools like pquery-prep-red.sh, pquery-clean-known.sh & pquery-results.sh
1. Quick re-cap and QA run setup
2. pquery-prep-red.sh
3. pquery-clean-known.sh
4. pquery-results.sh
5. Bonus: pquery reach – pquery-reach++.sh
We’ll also introduce the text_string.sh tool which extracts a most-specific text string from the error log in order […]

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MySQL QA Episode 5: Preparing Your QA Run with pquery

Welcome to MySQL QA Episode #5! In this episode we’ll be setting up and running pquery for the first time… and I’ll also trigger some actual bugs (fun guaranteed)! I’ll also introduce you to mtr_to_sql.sh and pquery-run.sh.
pquery-run.sh (the main wrapper around pquery) is capable of generating 80-120 MySQL Server crashes – per hour! See how […]

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MySQL QA Episode 3: How to use the debugging tool GDB

Welcome to MySQL QA Episode 3: “Debugging: GDB, Backtraces, Frames and Library Dependencies”
In this episode you’ll learn how to use debugging tool GDB. The following debugging topics are covered:
1. GDB Introduction
2. Backtrace, Stack trace
3. Frames
4. Commands & Logging
5. Variables
6. Library dependencies
7. c++filt
8. Handy references
– GDB Cheat sheet (page #2): https://goo.gl/rrmB9i
– From Crash to testcase: https://goo.gl/3aSvVW
Also expands on […]

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