Some time ago, Peter Zaitsev posted a blog titled “How well does your table fits in innodb buffer pool?” He used some special INFORMATION_SCHEMA tables developed for Percona Server 5.1 to report how much of each InnoDB table and index resides in your buffer pool.

As Peter pointed out, you can use this view into the buffer pool to watch a buffer pool warm up with pages as you run queries. You can also use it for capacity planning. If you expect some tables need to be fully loaded in the buffer pool to be used efficiently, but the buffer pool isn’t large enough to hold them, then it’s time to increase the size of the buffer pool.

The problem, however, was that system tables change from version to version. Specifically, the INNODB_BUFFER_POOL_PAGES_INDEX table no longer exists in Percona Server 5.6, and the …

I helped a charity to rebuild a MySQL server and to restore a database with a lot of data of longblob type in the last two days. Fortunately there was a dump backup file for the database in question.

However, tables with longblob column(s) were not defined with “ROW_FORMAT=COMPRESSED”. I’d like to restore that database with row compression before inserting the data. Therefore I need to modify the dump sql file. The problem is that the file is 2.5 GB and the server only has 4 GB memory. So editing it is a challenge. Fortunately, Linux has sed to save the day. Don’t you love open source free software?

I am power Vi/Vim user, so I am familiar with sed and have used it in the past. But there are still a few things that I searched around for quick answers. So I’ll record noteworthy points here. I couldn’t remember how many times my own past blog entries helped me over the years. And I hope you’ll find this helpful too! …

The Brainiac Corner is a format where we talk with some of the smartest minds in the system, database, devops, and IT world. If you have opinions on pirates, or anything else related, please don’t hesitate to contact us. 

Today, we interview Silvia Botros, the current Database Administrator at Sendgrid.

How did you get from stork to brainiac (i.e. what do you do today and how did you get there)?

I was a late bloomer to using computers at all. Having grown up in Egypt in a middle class family, I didn’t own a computer until I was in my second year of college. That was when I realized my love of Mathematical Logic could easily translate into telling a computer a set of commands and actually get some result.   After my move to the US and finishing college in California, I took a job in New York as a Junior Software Engineer …

Since Ruby on Rails 4.2 has just been released, perhaps now is a good time to review creating a shiny new Rails project. It’s not often I get to create a new project from scratch, but it’s Christmas and I’ve got a bit of downtime — and an itch I’d like to scratch! So, let’s get started.

I’m aiming to build a wee project that keeps track of OmniFocus perspectives. I’ve noticed that people are sharing their perspectives as screenshots and descriptions, in tweets and blog posts. Wouldn’t it be awesome if there was a one-stop-shop for everybody’s perspectives?

A couple of early decisions in terms of the basic starting point:

• Chances are I’ll deploy the app onto Heroku, so it’s a no-brainer to start out by using PostgreSQL in development. (Even …

Today I was doing some tests with XA transactions in MySQL 5.6.

The output of the XA RECOVER command to list transactions was hard to read because of the representation of the data column:

The good news is that 5.7 has transaction information in performance_schema:

mysql> select trx_id, isolation_level, state, xid, xa_state, access_mode 
    -> from performance_schema.events_transactions_current;
+-----------------+-----------------+--------+--------+----------+-------------+
| trx_id          | isolation_level | state  | xid    | xa_state | access_mode |
+-----------------+-----------------+--------+--------+----------+-------------+
|            NULL | REPEATABLE READ | ACTIVE | x-1    | PREPARED | READ WRITE  |
| 421476507015704 | REPEATABLE READ | …

Somebody ran into the following error message trying to query the innodb_sys_foreign and innodb_sys_foreign_cols tables from the information_schema database:

      ERROR 1227 (42000): Access denied; you need (at least one of) the PROCESS privilege(s) for this operation

It’s easy to fix the error, except you must grant the PROCESS privilege. It’s a global privilege and it should only be granted to super users. You grant the privilege global PROCESS privilege to the student user with the following command:

GRANT PROCESS ON *.* TO student;

Then, you can run this query to resolve foreign keys to their referenced primary key column values:

SELECT   SUBSTRING_INDEX(f.id,'/',-1) AS …

Hey,
Its fairly common. Please refer – http://dev.mysql.com/doc/refman/5.5/en/replication-howto.html

First step of successful MySQL data recovery is to find InnoDB pages with your data. Let’s call it first, because prerequisite steps are already done.

InnoDB page type is a two bytes integer stored in the header of a page. For MySQL data recovery two are important:

• FIL_PAGE_INDEX. Pages of this type are nodes of B+ Tree index where InnoDB stores a table.
• FIL_PAGE_TYPE_BLOB. So called external pages, where InnoDB keeps long values of BLOB or TEXT type.

stream_parser reads a stream of bytes, finds InnoDB pages and sorts them per type, per index or page id. It applies sophisticated algorithms tailored for particular page type. Of course, it assumes that page type in the header corresponds to the content of the page, otherwise it will ignore the page.

…

Join 28,000 others and follow Sean Hull on twitter @hullsean. MySQL slow query on RDS If you run MySQL as your backend datastore is there one thing you can do to improve performance across the application?. Those SQL queries are surely key. And the quickest way to find the culprits is to regularly analyze your […]

So I noticed a few different questions and posts about parsing a string out of another string recently. While some solutions included creating new functions and etc it can also be done within a single query in some cases.

For example, let us say that we are looking to pull out the domain from a URL. I will try to go into detail as to why and how this works.
We have the following table.

CREATE TABLE `parse_example` (
  `id` int(11) NOT NULL AUTO_INCREMENT,
  `urldemo` varchar(150) NOT NULL,
  PRIMARY KEY (`id`)
) ENGINE=InnoDB;
+----+----------------------------+
| id | urldemo                    |
+----+----------------------------+
|  1 | http://www.mysql.com/      |
|  2 | …