I had reason to look into the extended secondary index code in MariaDB and MySQL recently, and there was one bit that I really didn’t like.

MariaDB:

share->set_use_ext_keys_flag(legacy_db_type == DB_TYPE_INNODB);

MySQL:

use_extended_sk= (legacy_db_type == DB_TYPE_INNODB);

In case you were wondering what “legacy_db_type” actually does, let me tell you: it’s not legacy at all, it’s kind of key to how the whole “metadata” system in MySQL works. For example, to drop a table, this magic number is used to work out what storage engine to call to drop the table.

Now, these code snippets

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A while back one of my foreign keys started causing trouble. The problem was that some parent rows had tens of thousand of child rows, and the foreign key was defined with CASCADE DELETE enabled. When we deleted one of those parent rows on a master database, it took several seconds to execute the delete because of the cascade. This led to latency for the end user, and also led to replication delays.

The immediate solution was make the application tolerant of orphaned rows in the child table and to drop the explicit foreign key constraint.

I didn't really want to leave those orphaned rows hanging around in the child table, so I decided to implement an asynchronous process to delete the orphaned rows on a scheduled basis. Read on for a description of that process.

Using the

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It is finally here.  After three years of development, the new version of Shard-Query is finally available for broad testing.

This new version of Shard-Query is vastly improved over previous versions in many ways.  This is in large part due to the fact that the previous version of Shard-Query (version 1.1) entered into production at a large company.  Their feedback during implementation was invaluable in building the new Shard-Query features.   The great thing is that this means that many of the new 2.0 features have already been tested in at least one production environment.

This post is intended to highlight the new features in Shard-Query 2.0.  I will be making posts about individual features as well as posting benchmark results.

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Most serious users of MySQL have moved their tables to InnoDB years ago.  For those who haven't, let's discuss why InnoDB is a more scalable solution than MyISAM. MyISAM was designed to be very fast for read queries.  It does not handle higher loads of writes very well.  It also suffers a more serious flaw: it isn't crash-safe.  In other words, you better have frequent backups. MyISAM tables

I was sincerely affected by this last MySQL post and this other very long post from Jeremy Cole.
Yes, these two guys are MySQL rock stars and they are really impressives, their involvement in the MySQL community is utter!

I don’t want to write a long long speech about my simple life…
I just want to clarify why I do what I do.

Many people have asked or wondered without asking why I do what I do
(Jeremy Cole - 2013)

A few years ago Ashley Unitt asked me what I was most proud of, and now, I can make a complete answer. I’m very proud to take part of a community, MySQL has transformed my job into a passion and an incredible desire to share this

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I've already shared my presentation few hours before I made it during PLMCE 2013, back on April 24. Let's just have it here for the reference: http://www.slideshare.net/ValeriyKravchuk/mysql-56experiencesbugssolutions50mins.

During the upcoming weeks I plan to explain every slide in more details (as 50 minutes were not enough for this) here and check status of all the active bugs mentioned in it. I'll also check new bugs for each major feature mentioned (if any). So, stay tuned...

I was playing around with MySQL 5.7 this weekend and before having read the changelog, I managed to spot these two little gems.

Duplicate Indexes

“The server now issues a warning if an index is created that duplicates an existing index, or an error in strict SQL mode.” Bug #37520

Example Testcase:

mysql> SHOW CREATE TABLE city\G
*************************** 1. row ***************************
       Table: city
Create Table: CREATE TABLE `city` (
  `ID` int(11) NOT NULL AUTO_INCREMENT,
  `Name` char(35) NOT NULL DEFAULT '',
  `CountryCode` char(3) NOT NULL DEFAULT '',
  `District` char(20) NOT NULL DEFAULT '',
  `Population` int(11) NOT NULL DEFAULT

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Everybody seems to be looking at and debating NoSQL these days, and so am I and I thought I'd say a few words about it. Which is not to say I haven't said stuff before, bit them I was mainly targeting specific attributes of many NoSQL solutions (like "eventual consistency" or, as you might call it, "instant inconsistency", What I was opposing is that "eventual consistency" has anything to do with just that, consistency. Rather, what this means is that at any point in time the system is inconsistent, and even if it might be consistent, you cannot rely on it being so. Which is fine, but don't call it consistency, call it inconsistency. Allowing a database to be somewhat inconsistent doesn't necessarily mean that it's something wrong with it).

All this said, what is going on here, why are we MySQL and MariaDB users seeing so many

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343 revisions after the 7.0 release follows the new 8.0 release of HeidiSQL now.

Get it from the download page.

Here are the most noticable changes:


- Available in 23 languages now. Thanks to all translators and Transifex hereby!
- Database tree: Introduce optional folders for tables, views, routines etc.
- Introduce session folders in session manager.
- Make routine editor work on MS SQL servers.
- Support search and replace in data and query results.
- Add support for microseconds in temporal datatypes of MariaDB 5.3+ and MySQL 5.6.
- Introduce a query history, available in the right side helpers box. Can be turned off.
- Implement grid export as PHP array.
- Host > Variables: Add "Global" column, and highlight values different to their session














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I used a simple workload with sysbench to determine the rate at which InnoDB can read blocks from disk. The workload is read-only and each query fetches 1 row by PK. The workload was IO-bound with a 2G InnoDB buffer pool and 32G database. Storage was fast courtesy of buffered IO and enough RAM to cache the database in the OS filesystem cache.

Using MySQL 5.6.11 and InnoDB with a few hacks the peak throughput was about 240,000 QPS and 210,000 block reads/second. The test server has 32 cores (16 physical cores, 32 logical cores with HT enabled). This is a great result that can probably be even better. Contention on fil_system->mutex was the bottleneck and I think that can be improved (see feature request #69276). I wonder if 400,000 block reads/second is possible?

A few years back, in 2009 or 2010,



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Now that I'm back doing just database stuff, I've come to realize I've gotten a little sloppy about doing my homework.  Homework's never been my favorite thing in the world, but it often reduces stress when your under the gun during an outage or upgrade... We had a MySQL database server that's been slow on DML changes, and based on the slowest statements being 'COMMIT', we had a good mind

The red carpet has been laid down at this Log Buffer Edition, and you can witness and cheer the cat-walking blog posts from Oracle, SQL Server and MySQL. Every one of them is chic, elegant, sensual in its own right. Enjoy.
Oracle:

Create colored heat maps in SQL*Plus with Kyle Hailey.

Here’s a quick and dirty script to create a procedure (in the SYS schema – so be careful) to check the Hakan Factor for an object.

Connor has a good post about default null for collection parameter.

This is yet another blogpost on

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After a lot of fuzz, I am now releasing MyQuery version 3.5.1. This version introduces one big feature, a brand new Dictionary viewer. In addition to that, there are numerous bug fixes and the removal of one feature, which is the option to run with just 1 connection: In this version, 2 connections will always be used, and I have some good reasons to remove this as being optional, fact is, running with 1 connection was hard to diagnose, caused a lot of problems, and had no real benefit actually, just drawbacks.

So, for you Windows users, MyQuery 3.5.1 is now out there, but it is really a beta. The beta is caused by the new Dictionary viewer, the rest should be pretty stable.

Download it from sourceforge.

Happy SQLing
/Karlsson