This is part of the ongoing work on improving the transaction life cycle management. In 5.7.2 we split the transaction list into two. The read-only transaction list and the read-write transaction list. There was another "virtual" list, the auto-commit non-locking  read-only (AC-NL-RO) transaction list. The change in 5.7.2 was that by default a transaction was treated as read only and added to the read-only transaction list. Only when it was determined that the transaction was going to do an update we removed the transaction from the read-only list and moved it to the read-write transaction list. This initial add to the the read-only list forced the acquisition of the trx_sys_t::mutex. Acquiring the mutex during transaction start/begin has a cost. Promoting a transaction from read-only to read-write we had to acquire the trx_sys_t::mutex to add to the read-write transaction list and so that is not too expensive and unavoidable. There is another …

As we know, one of the most important config for InnoDB is the innodb_buffer_pool_size, it basically store the innodb data and indexes in memory, when MySQL receives a query and the InnoDB pages involved on that query are stored in the buffer, it does not need to go to the disk to return the result, which is much faster (memory speed vs disk speed).

As it is stored in memory, every time you restart your MySQL server it starts with a clean/empty buffer pool and usually it take some time to warm-up the buffer.
To speed up this process, we can configure 2 variables that will dump and reload the pages reference stored in the buffer, this is a new functionality added on MySQL 5.6 (it was presented on previous versions of Percona Server and MariaDB).

If you have your production server already running, we are going to set it to dump the content every time it shutdown:

SET GLOBAL innodb_buffer_pool_dump_at_shutdown = 1; …

This is part of the ongoing work on improving the transaction life cycle management. In 5.7.2 we split the transaction list into two. The read-only transaction list and the read-write transaction list. There was another “virtual” list, the auto-commit non-locking read-only (AC-NL-RO) transaction list. The change in 5.7.2 was that by default a transaction was treated as read only and added to the read-only transaction list. Only when it was determined that the transaction was going to do an update we removed the transaction from the read-only list and moved it to the read-write transaction list. This initial add to the the read-only list forced the acquisition of the trx_sys_t::mutex. Acquiring the mutex during transaction start/begin has a cost. Promoting a transaction from read-only to read-write we had to acquire the trx_sys_t::mutex to add to the read-write transaction list and so that is not too expensive and is unavoidable. There is another …

InnoDB Fulltext Search now supports plugin parser in MySQL 5.7.3 release. It is a compatible feature as for MyISAM Fulltext Search. So the syntax and usage remain to be largely the same.

A parser plugin can operate in either of two roles:

a) The plugin can replace the built-in parser. In this role, the plugin reads the input to be parsed, splits it up into words, and passes the words to the server (either for indexing or for word accumulation).

b) The plugin can act in conjunction with the built-in parser by serving as a front end for it. In this role, the plugin extracts text from the input and passes the text to the parser, which splits up the text into words using its normal parsing rules.

If you want to write your own full text plugin, please refer to http://dev.mysql.com/doc/refman/5.7/en/writing-full-text-plugins.html.

If you have a existing plugin parser for MyISAM, there would be some minor …

While troubleshooting deadlocks for a customer, I came around an interesting situation involving InnoDB gap locks. For a non-INSERT write operation where the WHERE clause does not match any row, I expected there should’ve been no locks to be held by the transaction, but I was wrong. Let’s take a look at this table and and example UPDATE.

mysql> SHOW CREATE TABLE preferences \G
*************************** 1. row ***************************
       Table: preferences
Create Table: CREATE TABLE `preferences` (
  `numericId` int(10) unsigned NOT NULL,
  `receiveNotifications` tinyint(1) DEFAULT NULL,
  PRIMARY KEY (`numericId`)
) ENGINE=InnoDB DEFAULT CHARSET=latin1
1 row in set (0.00 sec)
mysql> BEGIN;
Query OK, 0 rows affected (0.00 sec)
mysql> SELECT COUNT(*) FROM preferences;
+----------+
| COUNT(*) |
+----------+
|        0 |
+----------+
1 row in set …

As you probably already know, in MySQL 5.7.3 release, InnoDB Memcached reached a record of over 1 million QPS on a read only load. The overview of the benchmark and testing results can be seen in an earlier blog by Dimitri. In this blog, I will spend sometime on the detail changes we have made to achieve this number.

First thanks to Facebook's Yoshinori with his bug#70172 that brought our attention to this single commit read only load test. We have been focussing on operation with large batch size. This bug prompted us to do a series of optimization on single commit read only queries and these optimizations eliminate almost all major bottlenecks from the InnoDB Memcached plugin itself.

If you are just …

INFORMATION_SCHEMA is usually the place to go when you want to get facts about a system (how many tables do we have? what are the 10 largest tables? What is data size and index size for table t?, etc). However it is also quite common that such queries are very slow and create lots of I/O load. Here is a tip to avoid theses hassles: set innodb_stats_on_metadata to OFF.

This is a topic we already talked about, but given the number of systems suffering from INFORMATION_SCHEMA slowness, I think it is good to bring innodb_stats_on_metadata back on the table.

The problem

Let’s look at a system I’ve seen recently: MySQL 5.5, working set fitting in memory but not the whole dataset, around 4000 InnoDB tables.

The I/O load is very light as …

MySQL has exceptional track of record by introducing minor fixes that cause major breakages. Though usually I could blame naiveté of engineers, who did not really ever have to deal with production implications, but lately I can start sensing various business implications against open-source offerings.

As an original author of mydumper I really cannot get out of my mind that 5.5 and 5.6 metadata locking changes are there to screw with anyone who is building a backup solution using stable snapshot views of MySQL (for example, mysqldump –single-transaction, the golden standard of backing things up in MySQL world).

As seen in a bug #71017 (palindrome!) filed by my esteemed colleague Eric, newly introduced behaviors …

Or I could place in the title – “Yes, we done it!”

After reaching 500K QPS in Read-Only on SQL queries, it was natural to expect a much higher performance level from InnoDB Memcached Plugin which is by-passing all SQL related layers.. However the story is not simple, and yet far from finished

While for today we have already our first “preview” results showing that we’re able to reach over 1,000,000 Query/sec level with the latest MySQL 5.7 code:

click here to read the full article..

In MySQL 5.6 InnoDB has a dedicated thread (page_cleaner) that’s responsible for performing flushing operations. Page_cleaner performs flushing of the dirty pages from the buffer pool based on two factors:
- access pattern  -  the least recently used pages will be flushed by LRU flusher from LRU_list when buffer pool has no free pages anymore;
- age – the oldest modified non-flushed pages are part of flush_list structure and will be flushed by flush_list flusher based on several heuristics.

There is a good overview of the page_cleaner and also here you may find some details about flushing in MySQL 5.6. Below I describe several additional aspects of the flush_list flushing that was not really …