In this blog, I provide answers to the Q & A for the Troubleshooting hardware resource usage webinar.

First, I want to thank everybody who attended the May 26 webinar. The recording and slides for the webinar are available here. Below is the list of your questions that I wasn’t able to answer during the webinar, with responses:

Q: How did you find the memory IO LEAK?

A: Do you mean the replication bug I was talking about in the webinar? I wrote about this bug …

In this blog, I will provide answers to the Q & A for the Troubleshooting Slow Queries webinar.

First, I want to thank you for attending the April 28 webinar. The recording and slides for the webinar are available here. Below is the list of your questions that I wasn’t able to answer during the webinar, with responses:

Q: I’ve heard that is a bad idea to use

select *

; what do you recommend?

A: When I used

SELECT *

 in my slides, I wanted to underline the idea that sometimes you need to select all columns from …

Too often developers and DBAs struggle to pinpoint the root cause of MySQL database performance issues, and then spend too much time in trying to fix them. Wouldn’t it be great to bypass wasted guesswork and get right to the issue?

In our upcoming webinar Tired of MySQL Making You Wait? we’re going to help you discover how to significantly increase the performance of your applications and reduce database response time.

In this webinar, Principal Architect Alexander Rubin and Database Evangelist Janis Griffin will provide the key steps needed to identify, prioritize, and improve query performance.

They will discuss the following topics:

• Wait time analytics using …

Thanks to all who attended my webinar Introduction to MySQL SYS Schema. This blog is for me to address the extra questions I didn’t have time to answer on the stream.

Can i have the performance_schema enabled in 5.6 and then install the sys schema? Or they are one and the same?

You need to have enabled the performance_schema in order to use it through the sys schema. They are different entities. In general, performance_schema collects and stores the data, and sys schema reads and presents the data.

The installation of sys schema on primary database will be replicated to the slaves?

By default, no. If you wish that the Sys Schema replicates to the slaves, you can modify the before_setup.sql ( …

Thank you for attending my July 22 webinar titled “Advanced Query Tuning in MySQL 5.6 and 5.7” (my slides and a replay available here). As promised here is the list of questions and my answers (thank you for your great questions).

Q: Here is the explain example:

mysql> explain extended select id, site_id from test_index_id where site_id=1
*************************** 1. row ***************************
           id: 1
  select_type: SIMPLE
        table: test_index_id
         type: ref
possible_keys: key_site_id
          key: key_site_id
      key_len: 5
          ref: const
         rows: 1
     filtered: 100.00
        Extra: Using where; Using index

why is site_id a covered index for the query, given the fact that a) we are selecting “id”, b) key_site_id only …

Thank you for attending my July 15 webinar, “Creating Best in Class Backup solutions for your MySQL environment.” Due to the amount of content we discussed and some minor technical difficulties faced near the end of webinar we have decided to cover the final two slides of the presentation along with the questions asked by attendees during the webinar via this blog post.

The slides are available for download. And you can watch the webinar in it’s entirety here.

The final two slides were about our tips for having a …

Have you ever wondered what could happen if your MySQL database goes down?

Although it’s evident such a crash will cause downtime – and surely some business impact in terms of revenue – can you do something to reduce this impact?

The simple answer is “yes” by doing regular backups (of course) but are you 100% sure that your current backup strategy will really come through when an outage occurs? And how much precious time will pass (and how much revenue will be lost) before you get your business back online?

I usually think of backups as the step after HA fails. Let’s say we’re in M<>M replication and something occurs that kills the db but the HA can’t save the day. Let’s pretend that the UPS fails and those servers are completely out. You can’t failover; you have to restore data. Backups are a key piece of “Business Continuity.” Also factor in the frequent need to restore data that’s been …

Last week I hosted a webinar on using MySQL in the cloud for High Availability (HA) alongside 451 Research analyst Jason Stamper. You can watch the recording and also download the slides (free) here. Just click the “Register” button at the end of that page.

We had several excellent questions and we didn’t have time to get to several of them in the allotted time. I’m posting them here along with the answers. Feel free to ask follow-up questions in the comments below.

Q: Can the TokuDB engine be used in a PXC environment?

A: No, TokuDB cannot currently be used in a PXC environment, the only supported engine in …

MySQL sharding is one of the most used and surely the most abused MySQL scaling technology. My April 2 Dzone article, “To Shard, or Not to Shard,” proved there is indeed quite an interest in this topic.

As such, I’m hosting a live webinar tomorrow (April 22) that will shed light on questions about sharding with MySQL. It’s titled: To Shard or Not to Shard That is the Question!

I’ll be answering questions such as:

• Is sharding right for your application or should you use other scaling technologies?
• If you’re sharding, what things do you need to consider and which questions do you need to have answered?
• What kind of specific technologies can assist you with sharding?

I hope …

MongoDB 3.0 was recently released. Instead of focusing on what’s new – that is so easy to find, let’s rather talk about something that has not changed a lot since the early MongoDB days. This topic is sharding and most specifically: how to choose a good sharding key. Note that most of the discussion will also apply to MySQL, so if you are more interested in sharding than in MongoDB, it could still be worth reading.

When do you want to shard?

In general sharding is recommended with MongoDB as soon as any of these conditions is met:

• #1: A single server can no longer handle the write workload.
• #2: The working set no longer fits in memory.
• #3: The dataset is too large to easily fit in a single server.

Note that #1 and #2 are by far the most common reason why people need sharding. Also note that in the MySQL world, #2 does not imply that you need sharding.

…