EXPLAIN FORMAT=JSON

The regular

EXPLAIN

 command already provides some information about subquery optimization. For example, you can find out if the subquery is dependent or not, and (since version 5.6) if it was materialized:

mysql> explain select dept_name from departments where dept_no in (select dept_no from dept_manager where to_date is not null)G
*************************** 1. row ***************************
           id: 1
  select_type: SIMPLE
        table: departments
   partitions: NULL
         type: index
possible_keys: PRIMARY
          key: dept_name
      key_len: 42
          ref: NULL
         rows: 9
     filtered: 100.00
        Extra: Using where; Using index
*************************** 2. row ***************************
           id: 1
  select_type: SIMPLE
        table: …

I really like Amazon.com and I have been a Prime member for several years. Along with millions of different items for sale, Amazon has an affiliate program, where you can earn money advertising products on your web site. When a visitor to your site clicks on a link and orders a product from Amazon, you earn a small commission on the total sale. As an affiliate, you have access to Amazon’s Product Advertising API for obtaining product information. But, you can use this information for many other purposes.

The Amazon API is like most other API’s, and their API web site provides you with code examples and explains how it all works. I am going to show you how a Perl program which you can use to access the API data and store it in a …

Secure communications is a core component of a robust security policy, and MySQL Server 5.7.10 – the first maintenance release of MySQL Server 5.7 – introduces needed improvements in this area.  Support for TLS has been expanded from TLSv1.0 to include TLSv1.1 and TLSv1.2, default ciphers have been updated, and controls have been implemented allowing both server and client-side configuration of acceptable TLS protocol versions.  …

VMware Continuent 5.0 is a complete data replication solution that includes all the functionality you need at one low price. In this webinar-on-demand, you’ll see how VMware Continuent delivers:  Migration. Replicate from an old version of Oracle, often running on non-Linux platform (Windows, AIX, HP-UX, Solaris), to a new version of Oracle (often running in Linux). VMware Continuent supports

High Availability

Have you ever wondered if your application should be able to work in read-only mode? How important is that question?

MySQL seems to be the most popular database solution for web-based products. Most typical Internet application workloads consist of many reads, with usually few writes. There are exceptions of course – MMO games for instance – but often the number of reads is much bigger then writes. So when your database infrastructure looses its ability to accept writes, either because traditional MySQL replication topology lost its master or Galera cluster lost its quorum, why would you want to the application to declare total …

This blog continues the investigation into possible data races in the MySQL server reported by the Thread Sanitizer.  The previous blog investigated several possible data races that were detected when the MySQL server is initialized.  This blog investigates three data races in the performance schema that are reported when the MySQL server is shut down.  The first data race is a racy increment of thread statistics.  The second data race is a problem that may leave the state of the performance schema memory allocator incorrect.  The final data race is in the lock …

In our last post, we showed you how to use pt-stalk to help gather a bunch of data that can be used for troubleshooting. But what type of data does it collect? How do we parse the files to make sense of all that data?

This is the twentieth installment in the ‘Become a MySQL DBA’ blog series. Our previous posts in the DBA series include:

• Troubleshooting with pt-stalk,
• Troubleshooting Galera cluster issues - part 2,
• …

Performance Schema

In many types of database workloads, using a multi-threaded slave from 5.6+ helps improve replication performance. I’ve had a number of users enable this feature, but have not seen anyone ask how each thread is performing. Here’s a quick way with Performance_Schema to measure the amount of multi-threaded slave activity on each thread (after you have already configured MTS on your slave of course ).

First, we need to enable the 

statements

 instruments:

slave1> UPDATE setup_consumers SET ENABLED = 'YES' WHERE NAME LIKE 'events_statements_%';
Query OK, 2 rows affected (0.00 sec)
Rows matched: 3  Changed: 2  Warnings: 0

Next, let’s find the

THREAD_ID

 for our slave workers:

slave1> SELECT THREAD_ID, …

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