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Showing entries 1 to 10 of 17104 10 Older Entries

Displaying posts with tag: mysql (reset)

MySQL QA Episode 10: Reproducing and Simplifying: How to get it Right
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Welcome to the 10th episode in the MySQL QA series! Today we’ll talk about reproducing and simplifying: How to get it Right.

Note that unless you are a QA engineer stuck on a remote, and additionally difficult-to-reproduce or difficult-to-reduce bug, this episode will largely be non-interesting for you.

However, what you may like to see – especially if you watched episodes 7 (and possibly 8 and 9) – is how reducer automatically generates handy start/stop/client (cl) etc. scripts, all packed into a handy bug tarball, in combination with the reduced SQL testcase.

This somewhat separate part is covered …

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on ORDER BY optimization
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Generally in MySQL we send queries massaged to a point where optimizer doesn’t have to think about anything. In our major user database environment 99.9% of queries don’t have alternative query plans available (either because of forced indexes or just straightforward Primary Key read). We have various other systems and from time to time we have to do SQL work there and chase optimizer errors.

There’re multiple places where optimizer can make a choice in very basic queries, for example:

  • Which index returns less rows
  • Which index can be used for ORDER BY

A query that I was looking asked a very basic question, on a job …

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MySQL replication monitoring 101
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Replication is the process that transfers data from an active master to a slave server, which reproduces the data stream to achieve, as best as possible, a faithful copy of the data in the master.

To check replication health, you may start with sampling the service, i.e. committing some Sentinel value in the master and retrieving it from the slave.


Sentinel data: Tap tap… Is this thing on?

If you want to make sure that replication is working, the easiest test is using replication itself to see …






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Why base64-output=DECODE-ROWS does not print row events in MySQL binary logs
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Lately I saw many cases when users specified option

--base64-output=DECODE-ROWS

  to print out a statement representation of row events in MySQL binary logs just to get nothing. Reason for this is obvious: option

--base64-output=DECODE-ROWS

  does not convert row events into its string representation, this is job of option

--verbose

. But why users mix these two options so often? This blog post is result of my investigations.

There are already two great blog posts about printing row events on the …

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Ansible and Loading MySQL Databases Part II
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Loading databases on virtual systems is not as straight forward as it should be. Last time the foundation for using Ansible was set down on our quest to be able to have fully functional database servers on virtual servers automatically. But that prompted a few of you to remind me that you do not always need Ansible.

Without Ansible
You can have Vagrant do the work. Modify the vagrant file to run a script to run a script when …

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New! MySQL Connector/Arduino release-1.0.4 GA and Documentation
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After several iterations and a long period of community evaluation, I am happy to report I've released the newest, stable release of the MySQL Connector/Arduino. This library is designed to allow you to connect your Arduino via an Ethernet or WiFi shield to a MySQL database server running on your network (or the Internet!).

New Documentation!Best of all, I've written a reference manual that includes examples of how to use the connector in a variety of ways. Included in the document are advice on how to write your sketches, troubleshooting tips, and a long FAQ compiled from the many questions from my blogs.

Changes …



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New Optimizer Hints in MySQL
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The MySQL optimizer has a well known special system variable—optimizer_switch—which allows control of various optimizer modes such as index condition pushdown (ICP), batched key access, etc. One big disadvantage of using the optimizer_switch, however, is that changing its value is an extra step in the query execution. Another disadvantage of the …

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Pseudo GTID, ASCENDING
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Pseudo GTID is a technique where we inject Globally Unique entries into MySQL, gaining GTID abilities without using GTID. It is supported by orchestrator and described in more detail here, here and here.

Quick recap: we can join two slaves to replicate from one …

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Multi-source replication in MySQL 5.7 vs Tungsten Replicator
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MySQL 5.7 comes with a new set of features and multi-source replication is one of them. In few words this means that one slave can replicate from different masters simultaneously.

During the last couple of months I’ve been playing a lot with this trying to analyze its potential in a real case that I’ve been facing while working with a customer.

This was motivated because my customer is already using multi-sourced slaves with Tungsten Replicator and I wanted to do a side-by-side comparison between Tungsten Replicator and Multi-source Replication in MySQL 5.7

Consider the following scenario:

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About the new warnings generated during 'PURGE BINARY LOGS' execution
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In this blog, I will discuss about warnings that users might face if they are trying to purge active/in_use binary log which are introduced in MySQL-5.6.12/MySQL-5.7.2 releases.  Before jumping directly to that, I will be covering few basic things about PURGE BINARY LOGS command, about safe way to purge the binary logs on a replication forum. If you are good at basics on "PURGE BINARY LOGS" , you can choose to directly move to the section (at the end of the blog) where I was talking about these new warnings.

Introduction:
==========
A binary log file contains “events” that describe …



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Showing entries 1 to 10 of 17104 10 Older Entries

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