You are here: Home / Archives for Technologies / Databases

Log Buffer #47: a Carnival of the Vanities for DBAs

by

Log Buffer #47: a Carnival of the Vanities for DBAs
June 1st, 2007 – by Ronald Bradford

Welcome to the 47th edition of Log Buffer, the weekly review of database blogs. No time to wait, lets read more about this week’s database blogging activities.

The PostgreSQL Conference for Users and Developers wrapped up this week and Peter Eisentraut gives us a review including the lightning talks and wrap-up session with a charity auction in PGCon Day 4. Meanwhile Alex Gorbachev is at Miracle Scotland Database Forum – Day One, sounds like from his post there is a lot of drinking and tasting going on.

Tim Hall in Schema Owners and Application Users… starts with “I was trying to explain to a colleague the concept of using application users, rather than logging directly into the schema owner.” As he mentions, it’s an introductory topic however his article gives us a detailed discussion of implementation.

An OTN blog consolidates a number of announcements for Oracle, PHP and OPAL in it’s concise publication New PHP Doc and Software. Plenty of reading links here.

Paul Moen of Pythian covers an important step in Oracle: Standby Automatic File Management follows on from his earlier posts in creating a standby database.

Roland Bouman in MySQL User Defined Function Repository has made an effort to build a central repository of the varied UDF’s that exist to extend MySQL SQL Function syntax. His follow up article The MySQL UDF Repository: lib_mysqludf_sys shows just how dangerous these can really be.

Partitioning, a key new feature in MySQL 5.1 can be incorrectly used as Sergey Petrunia has described in Partition pruning tip: Use comparisons of column, not of partitioning function value. While 5.1 is not GA yet, and maybe not for some time Kevin Burton was quick to comment about software functionality about to be deployed with this new functionality. Of course partitioning in MySQL is free, in Oracle it is not as Mathias describes in Rant about partitioning licensing. Not only do you have to purchase the top of the line Enterprise Edition at 40K, you have to purchase an additional option on top of that. I didn’t know that.

Peter Zaitsev of the MySQL Performance Blog discusses Predicting how long data load would take. This is a very common problem particularly in a direct changeover of a production system to MySQL, and as with Peters example of loading 1TB, this is no longer an uncommon problem with MySQL.

Jag Singh from Optimize Data Warehouse uses a practical approach in Data type validation using regular expressions with a procedural language before data loading into a database, or performed within a database. It’s important we don’t lose site that some things are best done not in the database.

Slashdot starts a flame war with aptly titled 8 Reasons Not To Use MySQL (And 5 To Adopt It) with a reference between Five Compelling Reasons to Use MySQL and Eight Sound Reasons Not to Use MySQL, both published by CIO magazine on the same day. MySQL Performance Blog, and Curt Monash were quick to respond with MySQL – to use or not to use and Whether or not to use MySQL respectively.

Q&A Webinar Part 4 – MySQL Cluster by Ivan Zoratti gives us 33 points of reference with MySQL Cluster. Being involved with MySQL Cluster, it’s interesting to read the types of questions people are asking. Following up, Jonathan Miller a seasoned veteran with MySQL Cluster shows in Just when you think you know something that even the experts can be stretched with the new MySQL Cluster Certification Exam. Likewise I was surprised when I passed the exam myself recently of it’s complexity.

Andy Campbell in his blog Oracle Stuff I Should Have Known demonstrates he has too much spare time on his hand in understanding terminal colors in a novel but interesting Adding some colour to SQL*Plus. Would have looked better with some blue!

One of the features I promote in MySQL, and that exists in other RDBMS’, but Oracle does not have is native Multirow Inserts. Robert Vollman however provides Oracle’s two verbose alternatives. Only knew about one of them myself. Still they are far from the simplicity other database products have.

Brian Duff of DuffBuff writes If I had five Oracle wishes, they would be…. We all have wish lists and Brian writes, “I was thinking about things in the Oracle-sphere that I’d love to see happen over the next few years”. I won’t spoil his wish list, I think point 4 is a good one.

Using the OUTPUT and OUTPUT INTO clauses in SQL Server 2005 describes the new features for retrieving values that were just inserted/updated/deleted by a DML statement. Vardecimal Storage Format in SP2 discusses another new feature in SQL Server 2005, the new Vardecimal format. The caveat being that this functionality is restricted to the Enterprise and Developer Editions. One using SQL Server should also know about the Swiss-knife features in SQL Server to help you.

Things to take care before installing SQL Server 2005 on Vista operating system or Windows Server 2008?. Nothing more to say here, perhaps you need to read if your a SQL Server user.

Data Geek Gal Beth touches on one of my pet peeves in Data Quality: As Meets the Needs of an Organization. If data has a structure, appropriate rules should be put in place to ensure this is maintained in the database. You will forever be doing data cleansing if you simply bother to consider this basic step later. Developers should really learn to be smarter in this area. One point not discussed is, “Where are the validation rules applied, the application or the database?”

I’m not sure if a Log Buffer has had any images before, but I recently stopped at the Oracle HQ in Redwood city to snap this photograph. The irony of the experience not portrayed within the photograph was I worked for Oracle Corporation in the 1990’s but never visited the HQ, and while I was out taking this photo I was wearing a MySQL shirt. (No honking by any peak hour Oracle workers).

That’s it for this week, until next week. Clocks ticking Frank!

My ‘hourly’ MySQL monitor script Version 0.03

by

I realized when I released my very crappy version of My ‘hourly’ MySQL monitor script I really should have included my standard logging.

So I did that the night I wrote my original blog, but never published it. I’ve had need to use it again today, so a few more usability tweaks for parameterization and we are good to go.

Now Version 0.03 includes three files:

  • hourly.sh
  • common.sh
  • mysql.conf

Simple use is:

$ cd /directory
$ vi mysql.conf
# correctly specify MYSQL_AUTHENTICATION
$ chmod +x ./hourly.sh
$ nohup hourly.sh &

This gives you the following files

-rw-r--r-- 1 rbradford rbradford  2643 2007-05-29 15:47 mysql.innodbstatus.070529.154757.log
-rw-r--r-- 1 rbradford rbradford   414 2007-05-29 15:47 mysql.processlist.070529.154757.log
-rw-r--r-- 1 rbradford rbradford 12597 2007-05-29 15:47 mysql.status.070529.154757.log
-rw-r--r-- 1 rbradford rbradford 22229 2007-05-29 15:47 mysql.variables.070529.154757.log
-rw-r--r-- 1 rbradford rbradford 13146 2007-05-29 15:47 os.ps.070529.154757.log
-rw-r--r-- 1 rbradford rbradford   390 2007-05-29 15:48 os.vmstat.5.070529.154757.log

By default, written in /tmp, you can override by setting LOG_DIR.

It gives you a pile of output you can easily grep, I’m working on some very simple graphing. One thing I have done is pass the status into Mark Leith’s Aggregating SHOW STATUS Output as well as passed on some feedback that I hope will get integrated into later solutions.

For now, it’s a tool I can implement in a few seconds, run while somebody is showing or demonstrating a system, and I’ve got some meaningful information to look at. Combined with my more in-depth ‘minute’ script, a general-log and taking notes of individual steps in a system walk though, I have all the information I need to analyze a working system very quickly from a purely database level. Still there is lots to do manually, but I’ve got a consistent view of information to review.

Using Perl with MySQL

by

NOTE: Problems presently exist, I’m seeking the expert help of the community and Perl Gurus

I have the need to do some quick benchmarking, I use MyBench as it’s effective in being able to plug in a query, some randomness and 2 minutes later (with a correctly configured Perl/MySQL environment) you have multi-threaded load testing.

However, when the environment you are on is not configured, and you only know the basics for Perl Operation and Installation, (code is just code, that’s the easy part) and the box is not accessible to the outside world say for cpan, it gets more complicated. I’ve attempted to install and configure DBI, DBD::mysql and Time::HiRes but without success.

DBI
DBI was straightforward, a download, make, install worked without issue. a make install was performed.

DBD:mysql
DBD::mysql didn’t need an compile, mysql.pm already existed and make said it was all up to date. However then running mybench gave the first error.


failed: Can't locate DBD/mysql.pm in @INC

Ok, so it wasn’t installed as ‘root’. Some small Perl Pathing.


PERL5LIB=~/DBD-mysql-4.004/lib;export PERL5LIB

Let to the next error:


failed: Can't locate loadable object for module DBD::mysql in @INC (@INC

Hmmm, a little more complicated. So going back to the compiling part, I realized I could force compile it, and this also confirmed one possible issue, the libmysqlclient library.


perl Makefile.PL
I will use the following settings for compiling and testing:
cflags (mysql_config) = -I/path/to/mysql/include
embedded (mysql_config) =
libs (mysql_config) = -L/path/to/mysql/lib -lmysqlclient -lz -lcrypt -lnsl -lm
..

Both the mysql.h and libmysqlclient software correctly located and valid, but still no luck.

Moving in parallel I then managed a SA that could install the rpm’s (being RHEL). Problem is, MySQL is not installed via RPM, so the only possible means of installing DBD::mysql is to force no dependencies. This did not prove successful be added clues to the problem.


failed: Can't load '/usr/lib64/perl5/vendor_perl/5.8.5/x86_64-linux-thread-multi/auto/DBD/mysql/mysql.so' for module DBD::mysql: libmysqlclient.so.14: cannot open shared object file: No such file or directory at /usr/lib64/perl5/5.8.5/x86_64-linux-thread-multi/DynaLoader.pm line 230.

So it used the installed DBD::mysql, and it couldn’t find the expected library path. This gives some confident that perhaps the earlier version is right, and that some other dependancy is missing.

I’ve not found any good resource to work though this online in my environmental situation, but surely this is pain that somebody else has experienced.

Thanks for those friends that have already contributed small parts to getting someway here, however it just ain’t working, and I need it to just work.

Any input appreciated.

Everything fails, Monitor Everything

by


From the recent MySQL Conference a number of things resonate strongly almost daily with me. These included:

  1. Guy Kawasaki – Don’t let the bozos grind you down.
    • Boy, the bozos have ground me down this week. I slept for 16 hrs today, the first day of solid rest in 3 weeks.
  2. Paul Tuckfield – YouTube and his various caching tip insights.
    • I’ve seen the promising results of Paul Tuckfield’s comment of pre-fetching for Replication written recently by Farhan.
  3. Ramus – SSL is not secure — This still really scares me.
    • How do I tell rather computer illiterate friends about running multiple browsers, clearing caches, never visiting SSL sites after other sites that are insecure etc.
  4. Everything fails, Monitor Everything – Google

What I’ve been working on most briefly lately, and really want to be far more prepared everywhere I go is Monitor Everything.

It’s so easy on site to just do a vmstat 1 in one session and a mysqladmin -r -i extended-status | grep -v ” | 0 “ in another, and you may observe a trend, make some notes, say 25% CPU, 3000 Selects, 4000 Insert/Updates per second etc, but the problem is, the next day you don’t have actual figures to compare. What was the table_lock_waits yesterday, they seem high today.

I also only found a problem on a site when I graphed the results. I’ll give you a specific example. The average CPU for the system was 55%, the target was 50%. When graphing the CPU, it was plainly obvious something was not right. I could see with extremely regularity (and count 12 in one hour) a huge CPU spike for a second or two. It was so regular in the graph it was not possible it was random. So, after further investigation and testing, a 5 minute job on this production server (and not on previous testing servers) took 25% CPU for a second or two, and a huge amount of Page Faults. Did it effect the overall impact of the performance of the system. I don’t know, but it was a significant anonomoly that required investigation.

So, quite simply, always monitor and record so you can later reference, even if you don’t process the raw figures at the time. The question is then, “What do I monitor”. Answer, monitor everything.

The problem is with most monitoring, e.g. vmstat and mysqladmin is the lack of a timestamp for easy comparison. It’s really, really annoying that you can add this to the line output. The simple solution is to segment your data into both manageable chunks and consistent chunks.

Manageable chucks can be as easy as creating log files hourly, ensuring the start exactly at the top of the hour. Use a YYYYMMDD.HHMMSS naming standard for all files and you can never go wrong.
Consistent chunks is to ensure you start all manageable monitor (e.g. hourly) at the exact same time, so you can compare.

You need to monitor at least the following:

  • vmstat
  • mysqladmin extended-status
  • mysqladmin processlist
  • mysqladmin variables
  • mysqladmin -r -i [n] extended-status | grep -v ” | 0 “

I haven’t found an appropriate network monitoring, but you should also at that.

The issue here is frequency. Here are some guidelines. vmstat every 5 seconds. extended-status and processlist every 30 seconds, variables every hour, and extended-status differences is difficult, but it saves a lot of number crunching later for quick analysis. I do it every second, but not all the time, you need to work out a trigger to enable, or to say run it for 30 seconds every 15-30 minutes.

So in one hour I could have:

  • 20070519.160000.os.vmstat.log
  • 20070519.160000.mysql.variables.log
  • 20070519.160000.mysql.status.log
  • 20070519.160000.mysql.processlist.log
  • 20070519.160500.mysql.status.increment.log, then 1610, 1620, 1630 etc

I have my own scripts for monitoring under development, and I’ve been revising slowly, particularly to be able to load data into a MySQL database so I can easily use SQL for analysis. One thing I actually do is parse files into CSV for easy loading.

There are two tools out there that I’m reviewing and you should look at. Mark Leith has written a Aggregated SHOW STATUS stat pack, and there is also tool called mysqlreport. These both go some what to ultimately what I want.

I haven’t used it yet, but I’ve seen and been very impressed with the simplicity of Munin for graphing. I really need to get some free time to get this operational.

So Monitor Everything and Graph Everything. Plenty of work to do here.

Reading the right MySQL Manual

by

I learned an extremely valuable lesson today on a client site. It’s important that users of MySQL read the right version of the manual for the product they are using. It’s very easy to just goto http://dev.mysql.com/doc/ which is what I type in directly and browser the manual. While the MySQL Manual has separate sections for 4.x, 5.0, 5.1 etc, the 5.0 Manual for example reflects the most current version of MySQL 5.0. You may not be running the most current version, infact most production systems rarely run the current version.

My specific case was with Connector/J (JDBC) Reference of 5.0.4. The manual pages reflects the new 5.0.5 or todays’ 5.0.6 release and a particular default is now a different value. With Connector/J the docs are bundled with the version. The MySQL Community Server product does not bundle the manual, and I don’t know where to view instances of the MySQL manual for each specific dot release!

The MySQL Conference recap

by

I recently had the opportunity to return and speak at the Brisbane MySQL Users Group. I spent some time talking about MySQL User Conference 2007 Summary and Life as a Consultant. My summary of included:

  • Overview
  • Keynotes
  • Marten Mickos – MySQL
  • Guy Kawasaki
  • Michael Evans – OLPC
  • Rasmus Lerdorf – PHP
  • Paul Tuckfield – YouTube
  • Community Awards
  • Product Road Map
  • Google
  • Storage Engines
  • Dorsal Source
  • What’s Next

One question was posed to me. “What new did MySQL do this year?” being from the last User Conference. MySQL did seem to not make a great impact at the conference over the successes of the previous year. I had to think some time to come up with the following list.

And most recently:

  • Open Source Database Vendor Partners with LINBIT to Jointly Promote & Support DRBD for MySQL Enterprise Read More
  • IBM DB2 as a Certified Storage Engine for MySQL on System i Read More

It’s hard to say if these are big ticket items or not, but it is definitely disappointing that 5.1 GA is still MIA. We stay tuned.

I also managed a much better response then from my Conference Presentation opening Slide.


“How can you tell an Oracle DBA has touched your MySQL Installation?”

MYSQL_HOME=/home/oracle/products/mysql-version
mysqld_safe –user=oracle &

Reading the MySQL Manual

by

I was asked the question today, “How do I show the details of a Stored Procedure in MySQL. The SHOW PROCEDURE ‘name’ didn’t work.”.

The obvious answer was SELECT ROUTINE_NAME,ROUTINE_DEFINITION FROM INFORMATION_SCHEMA.ROUTINES, given I like to use the INFORMATION_SCHEMA whenever possible. This lead me to think was is the corresponding SHOW command. A quick manual search got me to SHOW CREATE PROCEDURE.

What was interesting was not this, but the list of other SHOW commands I didn’t know. I did not know about SHOW MUTEX STATUS, SHOW OPEN TABLES and SHOW PROCEDURE CODE for example.

It pays if you have free time (who ever has that), to re-read the manual, or at least a detailed index regularly. I’m sure there are plenty more helpful tips out there. Now just what does the output of these new commands really do, and does it really help. If only I could get commands to the stuff I really want.

MySQL Cluster Certified

by

Jonathon Coombes recently blogged in MySQL Cluster Certified that he passed the MySQL Cluster DBA Certification as was the first Australian. Lucky for him I passed the exam after my presentation on the second day of the conference. I guess us Australian’s are leading the world!

As Jonathon said it was rather hard, certainly more difficult then the other DBA exams but nothing for an experienced Cluster DBA.

MySQL Conference – YouTube

by

MySQL Conference 2007 Day 4 rolled quickly into the second keynote Scaling MySQL at YouTube by Paul Tuckfield.

The introduction by Paul Tuckfield was; “What do I know about anything, I was just the DBA at PayPal, now I’m just the DBA at youTube. There are only 3 DBA’s at YouTube.”

This talk had a number of great performance points, with various caching situations. Very interesting.

Scaling MySQL at YouTube

Top Reasons for YouTube Scalability

The technology stack:

  • Python
  • Memcache
  • MySQL Replication

Caching outside the database is huge.

It a display of numbers of hits per day it was said “I can neither confirm or deny the interpretation will work here (using an Alexa graph)”. This is not the first time I’ve heard this standard “Google” response. They must get lessons by lawyers in what you can say.

Standardizing on DB boxes (but they crash almost daily)

  • 4x2ghz opteron core
  • 16G RAM
  • 12x10k scsi
  • LSI hardware raid 10
  • Replication played a big part in fixing
  • Get a reliable H/W supplier

Replication Lessons

  • You don’t worry about it when a replicas fail.
  • One thing that sucks, Innodb doesn’t recover very fast. It does that durability think, but it takes hours to finish recovering (was it going to finish)
  • How many backups can you restore. When you switch you a replica, are you sure it’s right?
  • Did you test recovery, did you test your backups.
  • replication was key to trying different H/W permutations to identify incompatible H/W (combinations of controllers/disks)
  • we got good at re-parenting/promoting replicas, really fast
  • we built up ways to clone databases as fast as possible
  • Excellent way to test tuning changes or fixes (powerful place to test things)
  • Keep “intentional lag”/Stemcell replicas – Stop SQL thread, keeps a server a few hours or a day behind. Say if you drop a table you have a online backup.
  • When upgrading, always mysqldump then reload, rather then upgrade database.
  • Don’t care about CPU’s. I want as much memory as possible, I want as many spindles as possible.
  • For YouTube 2-3 second lag is acceptable.

If you db fits in ram, great otherwise

  • Cache is king
  • Writes should be cached by raid controller (buffered really) not the OS
  • Only the db should cache reads (not raid, not Linux buffer cache)

Only DB should cache reads

  • Hit in db cache means lower caches went unused.
  • Miss in db cache can only miss in other caches since they’re smaller.
  • Caching reads is worse then useless. It’s serialized writes.
  • Avoiding serialization in reads reaps compounds benefits under high concurrency

An important lesson learned. Do no cache reads in F/S and Raid Controller.

Caching Lessons
Overcoming Mystery Serialization

  • Use O_DIRECT
  • vm.swappiness=1-5
  • if you’re >80% buys — your not doing I/O concurrently look at other figures e.g. 80% busy 8 I/O’s, next configuration 80%, only 4 I/O’s
  • Mirror in H/W strip in S/W

Scale Out

  • Writes are parallel to master, but serialized to replicas. We need true horizontal partitioning.
  • We want true independent masters
  • EMD – Even More Databases — Extreme Makeover Database
  • Slave transactions must serialize to preserve commit order (this is why replication is always way slower)
  • The oracle caching algorithm (that’s a small o) — predicting the future
  • Replication lags: one IO bound thread. You do know the future, commands are coming up serially.
  • Write a script to do reads, before updates coming up (because they are cache hits).
  • The diamond. For golive, play shards binlogs back to original master for fallback.

MySQL Conference – Get Behind Dorsal Source

by


In a community session yesterday at MySQL Conference 2007, I first heard about Dorsal Source. A collaboration between Solid DB and Proven Scaling that allows for community people to upload patches to MySQL, get it compiled across multiple platforms, and have a downloadable distribution available on H/W individual contributors will never have access to.

That’s a great idea. I also hope we get the opportunity to get compiling of patches into multiple versions, as well to get builds of a lot of patches together. Personally, I’m running 3 versions just to diagnose one problem. 5.0.36 with a custom binary change, 5.0.37 so I have SHOW PROFILE, and 5.0.33 so I have microslow patch.

With new patches becoming available from the community, I hope I can see builds that combine all known patches that Dorsal Source may have.

I think this is going to be a great project.

MySQL Conference – PHP on Hormones

by

MySQL Conference 2007 Day 4 started early again at 8:20 am with PHP on Hormones by the father of PHP Ramus Lerdorf.

A very funny man, one of the best insightful talks of the conference (rather scary actually). Here are some opening comments.

  • In his own words as Keynote speaker. “I’m here because I’m old”.
  • Php 1 from 1994 started after seeing Mozilla in 1993. Because it was just me using it, I could change the language any time.
  • In 2005 the code looks like this (in comparison on 1995) — I’m not sure if this is worth 10 years of development
  • I wrote PHP to avoid programming
  • It’s changed to be more OO because people expect that. Universities teach this.
  • Hey, I was fixing bugs in my sleep. Iwould wake up, and in my mail box there would be bug fixes to bugs I didn’t even know I had.

Why do people contribute?

  • Self-interest
  • self expression
  • hormones
  • Improve the world

The slide included a great Chemical equation of “The Neuropeptide oxytocin” — Nature’s trust hormone

People need to attract other people, it makes you feel good, it comes out when you interact with people.

It’s not what people think about you, but rather what they think about themselves.

  • PHP was my baby, giving up control, just because I started it, doesn’t mean I have a bigger say in it.
  • Systems that harness network effects and get better the more people use them in a way that caters to their own self-interest. — Web 2.0
  • Once you build a framework your done, the users build the site, they drive the content.
  • The same people that work on open source projects, are the same people that use websites.
    • Self-interest
    • self expression
    • hormones
    • Improve the world

1. Performance
It your sites falls apart your done.

  • Benchmark
    • http_load
    • Callgrind inside valgrind
    • XDebug

valgrind –tool=callgrind

  • Excellent tool to see where time is spent in the code. You have to run a profiler.
  • Example of using Drupal. It turns out 50% of time was spent in the them, it had 47 SQL queries, 46 Selects.
  • Went from 4 per second to 80 per second, without any code changes. Some performance options, and some caching.
  • Guaranteed you can double the speed of your website by using a profiler.

2. Security
Critical problem areas.

  • 404 pages
  • Search page
  • PHP_SELF
  • $_GET, $_POST, $_COOKIE
  • $_SERVER
  • Lots of stupidity in IE (e.g. Always send a charset)

The web is broken you can all go home now.

People are venerable because people run older versions of browsers, and their data is not secure, and you can’t secure their data.

What can happen??
9 out of 10 of you have cross-site scripting hole on your site

Remote Greasemonkey
Profile Hacks
JS Trojans

Added a PHP logo to the MySQL User Website, it’s really the PHP website
IBM webpage, on article about security.

Tool to find holes, banks, insurance companies, CIA, even Yahoo where I work.

You know if they have been to bankofamerica.com, you can tell if they are a customer, you can tell if they are logged, you can then see their cookie credentials.

You don’t know if any sites have these problems.

JS trojan, iframe that captures
reconfigures your wireless router, moves it outside your DMZ, then uses traditional techniques to attack your machine (that you thought was secure inside a firewall)

You should never ever click on a link. It sort of defeats the purpose of the web.

Never use the same browser instance to do personal stuff and browsing.

So what are we doing about this?
There isn’t much we (PHP) can do to secure sites developed.
Built a filter extension in 5.2, back in 5.1.

http://php.net/filter *** YOU MUST IMPLEMENT THIS
filter.default=special_chars

3. APIs are Cool!

Two lines to grap the Atom feed from flickr of photos just uploaded.
That’s all I have to add to my code.

The really make you want to use the servers. It’s so easy.

API drives passion, drive people to use your site.
You can add a lot of cool things to your sites.

What to do

  • Avoid Participation Gimmicks
  • Get their Oxytocin flowing
  • Solve One Problem
  • Clean and Intuitive UI
  • API’s
  • Make it work

A full copy of the slides can be found at http://talks.php.net/show/mysql07key

MySQL Conference – Google

by

MySQL: The Real Grid Database

Introduction

  • Can’t work on performance problems until we solve the availability
  • We want MySQL to fix our problems first.

The problem

  • Deploy a DBMS for a workload with
    • too many queries
    • to many transactions
    • to much data

A well known solution

  • deploy a grid database

    • -use many replicas to scale read performance
    -shard your data over many master to scale write performance
    -sharding is easy, resharding is hard

  • availability and manageability trump performance

    • – make it easy to run many severs
    – unbretable aggregate perfomance

  • we describe problems that matter to us.

    • The grid database approach

    • Deploy a large number of small servers
    • use highly redundant commodity components
    • added capacity has a low incremental cost
    • not much capacity lost when a server fails
    • support many servers with a few DBAs

    Managability
    Make it easy to do the tasks that must be done. Reduce, Reduce.
    Make all tasks scriptable
    Why does it mater, support hundreds of servers, spend time solving more interesting problems. You generally have lots of problems to solve.

    Underutilize your severs
    Require less maintenance
    Requre less tuning
    tolerate load spikes better
    tolerate bad query plans better

    In a Perfect World
    Short running queries
    uses kill mistake and runaway queries
    accounts new use to many connections
    query plans are good
    new apps increase database workload by a small amount
    only appropiate date is stored in the database

    Reality

    • Long running transactions, create replication delays everywhere
    • servers with round robin DNS aliases make queries hard to find
    • applications create more connections where the database is slow
    • some storage engines use sampling to get query plan statistics
    • new applications create new database performance problems
    • applications use the database as long as rows are never deleted
    • many long running queries on replicas

    Solutions

    • Improve your ability to respond because prevention is impossible
    • Need tools to make monitoring easier
    • determine what is happening across servers
    • detemine what happened in the past

    Mantra

    • Monitor everything you can, and archive as long as possible. (vmstat 5 secs, iostat, mysql error logs)
    • You will need these to reconstruct failures
    • save as much as possible
    • script as much as possible

    Monitoring Matters

    • Display what is happening

      • -which table, account or statemsns caused most of the load
      -many fast queries can be as much a problem as one slow query

    • Record what happending

      • –archivce show status counters somweere
      – query data from the archive
      — visualise data from the archivce

    • record queries that have been run

      • — archive show processlist output (do every 30 seconds)
      — support queries on this archive

    • All of this much scale to an environment with many servers

    Monitoring Tools

    • Display counters and rate change for counters
    • aggregate values over many servers
    • visualize and rang results
    • display results over time

    Google mpgrep tools

    New Commands
    We changed mysql, three new commands
    SHOW USER _STATISTICS
    SHOW TABLE STATISTICS
    SHOW INDEX STATISTICS

    Per Account Activity
    USER_STATISTICS
    seconds executing commands
    number of rows fetched and changed
    total connections
    number of select/updates/other/commits/rollback/binlog bytes written.

    TABLE STATISTICS
    number of rows fetched/changed

    INDEX STATISTICS
    display number of rows fetched per index
    helps find indexes that are never used

    available in code.google.com in 4.0, porting to 5.0

    MySQL High Availability

    • Great options
      • Cluster
      • Replication
      • Middelware — e.g. continum
      • DRBD
    • We need some features right now
    • we are committed to innodb and mysql replication

      • *a lot of appplicaton code works on this
      *our tools and processed support this

    • We favor commodity hardware

    There are all great features but we are much more limited in what we can use.
    Management want to know we don’t loose transactions, not loose some transactions.

    Desired HA Functionality

    • Zero transaction loss on failures of a master
    • minimal downtime on failures of a master
    • reasonable cost in performance and dollars
    • fast and automatic failover to local or remove server
    • no changes to our programming model
      • does it support MVCC

        • does it support long running transactions (5 mins – populate temp table then use to update another table, changing rows), 5 mins on master, causes 5 mins on slave, causes code to failover from slaves to master

    • replication and reporting are concurrent on a slave

    MVCC must have update concurrent with query.

    Failures happen everywhere
    OS – kernal oom or panic (older 2.4 32 bit systems)
    mysqld – caused also by code we added
    disk, misdirected write, corrupt write (love innodb checksums)
    file system – inconsisted after unplanned hardware reboot (use ext2)
    server – bad RAM
    lan, switch – lose
    Rack – reboot
    Data center – power loss, overheading, lightning, fire
    People – things get killed or rebooted by mistake ( a typo can take out the wrong server, when names differ by a character or a digit)

    ext2 and 4.0 are great, there are the same generation.
    Trying not to use RAID, not battery backed raid etc, we try work around with software solutions. We do use RAID 0, but we also try software solution.
    When we have the right HA solution, we won’t need RAID.

    Mark. “Yes, Google programmers have bugs. Not me personally, it was my predecessor.”

    HA Features we want in MySQL
    Synchronous replication as an option
    a product that watches a master and initiates a failover
    archives of the master binlogs stored elsewhere
    state stored in the filesytstem t obe consistent after a crash
    . innodb and mysql dictionaries can get out of sync
    .replicatoin state on a slave can get out of sync

    We could not wait
    Features we added to MySQL 4.0.26
    We can do things a lot faster
    . we have more developers lying around
    . Our needs as specific, not a general product solution

    Transactional replications for slaves
    semi-synchronous replication
    mirrored binlogs
    fast and automated failover

    Transactional Replication
    Replication state on a slave is stored in files
    slave sql thread commits to storage engines and then updates a file
    a crash between the two can make replication state inconsistent
    transactional replication
    MySQL can solve this in the future by storing replication state in tables

    Semi-synchronous replication
    Block return from commit on a master until at least one slave has acknowledged receipt of
    slave io thread acknowledges receipt after buffering the changes
    modified mysql replication protocol to support acknowledgments
    conifuration options
    where to the master uses it
    where a slave used it
    how long the maser waits for an acknowledgement

    can run a server with some semi-sync replication slaves and some regulare replication salves
    this can be worked with any storage engines that supports commit, but we only use innodb

    * This is how we guarantee to management for Zero Transaction Loss.

    Latency single stream 1ms, multi-stream 10ms. This is acceptable for us.

    The MySQL Replication Protocol

    • The current replication protocol is efficient
    • a slaves makes one request

    Replication Acknowledgment

      Slaves register as semi-sync or async at connect time
      prepend flag bytes to all replication events sent to semi-sync clients
      the master sends the flag bytes to request acknowledged for replication events that represent the end of the transaction
      the slave use the existing connection for acknowledgments

    Mirrored Binlogs
    mysql does not provide a way to maintain a copy of a master’s binlog on a replica. By copy we me a file of same name and equivalent byte for byte.
    Hierarachial replication works much better where a slave can disconnect from one replication proxy and reconnect to another with adjusting binlog offsets.
    Hot backups taken before a failover and difficult to use after a failover

    Mirrored Binlog Implementions
    Slave IO threads write their own relay log and a copy of the bin log
    all events but the rotate log event are written

    After failover, start a new binlog on new master

    Fast Failover

    Slaves use a hostname, rather then an IP
    You can’t enable the binlog dynamically (in 4.0)
    Added new SQL STATEMENTS that does
    disconnect users with SUPER privilege
    disable new connections
    enable the bin log
    enable connections from all users

    Automatic failover
    Something must decided that a master has failed
    Something must choose the new master

    Q: What keeps up from moving to 5.0?
    A: Queries don’t parse (Joins)

    Data sets, 8GB servers, 50-100GB’s

    MySQL Roadmap

    by

    Here are some notes from the MySQL Server Roadmap session at the MySQL Conference 2007.

    MySQL: Past and Future

    • 2001: 3:23
    • 2003: 4.0 UNION query Cache Embedded
    • 2004: 41. Subqueries
    • 2005: 5.0 Stored Procedures, Triggers, Views
    • Now: 5.1.17 Partitioning, Events, Row-based replication
    • 2007?: 6.0 Falcon, Performance, Conflict detection
    • 2008?: 6.1 Online Backup, FK Constraints

    2007 Timeline

    • Q1: 5.1 Beta, 5.1 Telco Production Ready, Monitoring Service 1.1, MySQL 6.0 Alpha, Community GA
    • Q2: MySQL 6.0 Beta, New Connectors GA
    • Q3: 5.1 RC, 6.0 Beta, MS 2.0, Enterprise Dashboard beta
    • Q4: 5.1 GA, 6.0 Beta

    Where are we today?

    • We are by fare the most populate open source database
    • The Enterprise world is moving online and MySQL is well-positioned for that trend, But:
      • Transactional scalability
      • Manageability
      • Specific online features

    MySQL Server Vision – The Future

    • Always Online — 24×7, Online backup,online analytics, online schema changes
    • Dynamic Scale-out — online partitioning, add node, replication aides,
    • Reliable — fault-tolerant, easy disagnosis, stable memory, ultimately self-healing
    • High-performance — Interactive web, real-time response, apps, 10,000-100,000 clients
    • Ease of use — Portable, Best for development, multiple connectors, easy tuning
    • Modularity and Ubiquity — Storage engines, plug ins

    How can you help?

    • Bug finding and fixing — Community Quality Contributor
    • Feature/patch contribution
    • But, to expedite your patch

    The goal: “Be the Best Online Database for Modern Applications”

    MySQL Conference – For Oracle DBAs and Developers

    by


    I have just completed my presentation at the MySQL Conference 2007 on MySQL for Oracle DBAs and Developers.

    Not mentioned in my slides, but referenced during the presentation was what I consider the most important page to document from the MySQL Manual — 5.2.1. Option and Variable Reference

    You can download a PDF copy of my presentation here.

    MySQL Conference – Building a Vertical Search Engine in a Day

    by

    Moving into the user sessions on the first day at MySQL Conference 2007, I attended Building a Vertical Search Engine in a Day.

    Some of my notes for reference.

    Web Crawling 101

    • Injection List – What is it seed URL’s you are starting from
    • Fetching the pages
    • Parsing the content – words and links
    • Updating the crawl DB
    • Whitelist
    • Blacklist
    • Convergence — avoiding the honey pots
    • Index
    • Map-reduce — split a large problem into little pieces, process in parallel, then combine results

    Focused content == vertical crawl

    • 20 Billion Pages out there, a lot of junk
    • Bread-first would take years and cost millions of lives

    OPIC + Term Vectors = Depth-first

    • OPIC is “On-line Page Importance Calculation”. Fixing OPIC Scoring Paper
    • Pure OPIC means “Fetch well-linked pages first”
    • We modify it to “fetch pages about MySQL first”

    Nutch & Hadoop are the technologies that run on a 4 server cluster. Sample starting with www.mysql.com in 23 loops, 150k pages fetched, 2M URL’s found .

    Serving up the results

    MySQL Conference – RedHat Keynote – One Laptop Per Child

    by

    Our third keynote at MySQL Conference 2007 was titled Building the Ultimate Database Container with RHEL, MySQL, and Virtualization by Michael Evans.

    The presentation was on Red Hat & One Laptop Per Child. His initial Quote was “Thinking Past Platforms: The Next Challenge for Linux”, By Doc Sears, 2007-04-16 http://www.linuxjournal.com/node/1000210

    OLPC

    • A Non profit idea from Nicholas Negroponte.
    • Aim is to build & distribute inexpensive laptop systems to primary & secondary school students worldwide.
    • Sell to young children in developing countries.

    In summary at presentation to Red Hat — “Non-profit, run by a professor, we make hardware and sell to governments.”

    The overall dynamics have attracted a lot of interesting people in the world.

    The ability and goal is to make the device together, bringing all H/W and S/W people together.

    The people that get behind this project have the ethos — “I’m willing to jump into this to change the world.”

    This is the first time for a new opportunity in the last 10 years.

    The sugar user interface is a completely new experience.

    When the UI designer was presenting to a room of head executives. “What ever advice you got, keep it to yourself, your not the target market.”

    One key point — No backward compatibility needs.

    More information at www.laptop.org. Wikipedia Reference. Some videos at You Tube Inside One Laptop per Child: Episode one and Slightly better demo of the OLPC User Interface.

    MySQL Conference – The next keynote with Guy Kawasaki

    by

    Without missing a beat at MySQL Conference 2007, we moved from Marten’s keynote to The Art of Innovation by Guy Kawasaki.

    Extremely fun and entertaining. His 10 points.

    1. Make Meaning

    • “To change the world”
    • To a VC, do not say “you want to make money”, that is understood. You will attract the wrong team.

    2. Make Mantra

    • Not a Mission statement (50-60 words long), but 2 or 3 words.
      • Wendy’s – “Healthy fast food”
      • Mike – “Authentic Athletic Performance”
      • FedEx – “Peace of Mind”
      • eBay – “Democratize commerce”
    • Create a mantra — Why do you exist?

    If you get stuck try the Dilbert mission statement generator.

    3. Jump to the next curve

    • Not 50% or 100% better, but “Do things 10x better”

    4. Roll the DICEE

    • “Create great stuff”
      • Deep: Fanning (Reef) Sandal that open beer bottles
      • Intelligent: BF-104 Flashlight (Panasonic) (takes 3 sizes of batteries)
      • Complete: Lexus
      • Elegant: Nano (Apple)
      • Emotive: Harley Davidson (They generate strong emotions)

    5. Don’t worry, be crappy

    Get it out there.

    6. Polarize people

    People love it or hate it.

    7. Let a hundred flowers blossom

    • People that are not your target market are using it.
    • Take the money, ask the people why you are buying, ask what you can do better.

    8. Churn baby, churn.

    Ok to ship stuff with crappy stuff in it, but important to continually revised and improve.

    9. Niche thyself
    With a nice graph.

    • Vertical — Ability to provide unique product or service
    • Horizontal –Value to customer
    • bottom right — Price
    • top left — Stupid
    • bottom left — Dotcom
    • top right — X You need to be High and to the right.
    • Fandango — It’s either Fandango, or Clubbin.
    • Breitling Emergency – watch
    • Smart car – park perpendicular
    • LG Kimchi refrigerator

    You need to be like the President of the United States – You need to high and to the right. Got a great laugh from the crowd.

    10. Follow the 10/20/30 rule

    Innovative, you need to pitch for what you want.

    • The optimum number of slides in 10 slides.
    • Given the slides in 20 minutes.
    • Use 30 point font

    11. Don’t let the bozos grind you down

    A bonus to our friends in the community.

    • “I think there is world market for five computers”
    • “This telephone has too many shortcomings to be seriously considered as a means of communication. The device is inherently of no value to us.” –Western Union 1876
    • “There is no reason why anyone would want a computer in their home.” — Digital Equipment Corp 1977
    • “It’s too far to drive, and I don’t see how it can be a business.” – Guy Kawasaki – Bozo (The company was Yahoo)

    Guy commenting on his lost opportunity with Yahoo — “It only covers the first billion, it’s the second billion that pisses me off.”

    Read more about Guy at his website Guy Kawasaki.

    The Art of Innovation. If you a copy of slides, send an email to [email protected]

    MySQL Conference – Opening Keynote with Marton Mickos

    by

    It’s an early start this morning at 8:20am at MySQL Conference 2007 with CEO Mårten Mickos keynote talk Welcome and State of MySQL AB.

    Here are some of the key points that impressed on me.


    “The Participatory & Disruptive spirit of the Dolphin.”.

    Open Source disrupts inefficient models and produces new wealth.

    Architecture of Participation.

    • GPL and FOSS licenses
    • Google
    • del.ico.us

    MySQL Architecture of Participation
    You have the forge, the planet, community contributer program and many more.

    Production of Amateurs

    • You Tube
    • Second Life
    • Wikipedia

    Some really great Quotes:

    “Fail often to succeed soon.” IDEO company slogan

    “Noah’s Ark was built by amateurs, but the Titanic by professionals.”

    Innovation Happens Here

    MySQL Monitoring & Advisory Service

    In his presentation of MySQL Network Enterprise Dashboard, If you were quick you would have noticed the MySQL Version 6.0.0-alpha-pb518.log

    Leading Applications

    • Open Source ISVs
    • Web
    • Web 2.0
    • On-Demand
    • Hosting
    • Telco & VOIP
    • Security
    • Enterptise 2.0
    • Hub & Spoke

    We want to be known as The Online Database.

    Drawn to the Lamp

    • Microsoft
    • Oracle
    • IBM
    • Sun
    • HP
    • Dell
    • Unisys

    They all have an Open Source strategy, the develop open source products, they use and partner with MySQL.

    He also mentioned MySQL Enterprise Connection Alliance – MECA.

    Global Distributed Organization

    • 70% work from home
    • 100 major locations in nearly 30 different countries.
    • There is a great focus on culture – global culture.

    Disruptive Businesses

    • A smarter way to produce the goods
    • A smarter way to distribute them
    • Serve the underserved
    • Keep it simple
    • Innovate with technology to give customers more convenience
    • Make money
    • Gartner: 66% of enterprises are deploying MySQL or planning to
    • 750,000 newsletter subscribers
    • MySQL installed in over 11 million installations

    Going Forward

    • Scalability
    • Availability
    • Manageability
    MySQL – The best online database in the world.

    MySQL Conference – Rewarding the Community

    by

    At MySQL Conference 2007, CEO Mårten Mickos in his opening keynote Welcome and State of MySQL AB rewarded the community. Those that contributed to “The best database in the world”.

    2007 MySQL Applications of the Year
    #1 in Online Video
    #1 in 3G Mobile Entertainment
    #1 in Creative Software

    And the Winners- YouTube, Amp’d mobile, and Adobe

    2007 MySQL Partners of the Year
    #1 reseller of MySQL Enterprise to govt
    #1 in MySQL Enterprise integration
    #1 in Open Source

    And the Winners – Carasoft, HP, and RedHat

    2007 Community Members of the Year
    Quality Contributor
    Community Code Contributor
    Community Advocate

    And the Winners

    Martin Freibe
    Paul McCullagh
    Sheeri Kritzer

    SHOW PROFILE

    by

    I’ve been playing more with the SHOW PROFILE command available as part of MySQL Community 5.0.37. Thanks to the author Jeremy Cole. This command can provide some interesting insight into the workings of MySQL. It does however like most new releases of software enable users to make suggestions for new features and functionality. Here is my wish list. Some I figure are practical, some are wish list, but if you never ask you never know.

    1. The Unit of measure for duration is Second. It would be great if it could be tuned for display, say millisecond. If you look at my first Example, all figures are effectively represented in milli-second or even micro-second granularity.
    2. I would like to see a total for the query. Again in Example 1, you have to add up all the figures to determine this query took 8ms.
    3. Again in Example 1, perhaps a percentage of total time for each line duration may be helpful.
    4. More descriptive status descriptions (this is part of the MySQL internal code and not the patch)
    5. SET PROFILING=1; can only be set on a current session, making it impossible to easily monitor a JDBC multi-connection test. There needs to be a way to enable for a session, other then current interactive one you are viewing, but also be able to see results. You can’t do a SHOW PROFILE via a JDBC connection!
    6. I’d like to see a threshold, so queries running under threshold are discarded, much like a long-query-time option. This enables you to run a large number of SQL Statements and only profiles for longer running ones are logged
    7. I’d like to see a level of logging to file, again like a slow query log, so you can simply gather information on a working system and review at some later time. Combined with the previous point, you now have microsecond slow query log with explicit details.

    One major benefit of the SHOW PROFILE command is I can accurately get a figure for how long a query it taking (time in milliseconds). You just have to sum all figures (See wish list point 2).

    By default, the source details are not provided, you need to specify the SOURCE operand, which helps in both comparing with any debugging output and also trouncing through the code. As in Example 1, I needed to find why 95% of time was in a step with the most descriptive line of ‘end’.

    Example 1

    mysql> show profile SOURCE,MEMORY for query 4;
+--------------------+------------+-----------------------+---------------+-------------+
| Status             | Duration   | Source_function       | Source_file   | Source_line |
+--------------------+------------+-----------------------+---------------+-------------+
| Opening tables     | 0.00013200 | open_tables           | sql_base.cc   |        2106 |
| System lock        | 0.00001800 | mysql_lock_tables     | lock.cc       |         153 |
| Table lock         | 0.00000600 | mysql_lock_tables     | lock.cc       |         162 |
| init               | 0.00001300 | mysql_select          | sql_select.cc |        2073 |
| optimizing         | 0.00004800 | optimize              | sql_select.cc |         617 |
| statistics         | 0.00002500 | optimize              | sql_select.cc |         773 |
| preparing          | 0.00005200 | optimize              | sql_select.cc |         783 |
| executing          | 0.00002200 | exec                  | sql_select.cc |        1407 |
| Sending data       | 0.00000500 | exec                  | sql_select.cc |        1925 |
| end                | 0.00786600 | mysql_select          | sql_select.cc |        2118 |
| query end          | 0.00001400 | mysql_execute_command | sql_parse.cc  |        5085 |
| freeing items      | 0.00000700 | mysql_parse           | sql_parse.cc  |        5973 |
| closing tables     | 0.00001900 | dispatch_command      | sql_parse.cc  |        2120 |
| logging slow query | 0.00001000 | log_slow_statement    | sql_parse.cc  |        2178 |
| cleaning up        | 0.00000500 | dispatch_command      | sql_parse.cc  |        2143 |
+--------------------+------------+-----------------------+---------------+-------------+
15 rows in set (0.01 sec)

    Example 2

    We were experiencing increased latency in JDBC with a particular query, With a recommendation from MySQL Support we tried SET SQL_BUFFER_RESULT=1;

    mysql> show profile source for query 14;
+------------------------------+------------+-------------------------+---------------+-------------+
| Status                       | Duration   | Source_function         | Source_file   | Source_line |
+------------------------------+------------+-------------------------+---------------+-------------+
| Opening tables               | 0.00006025 | open_tables             | sql_base.cc   |        2106 |
| System lock                  | 0.00004875 | mysql_lock_tables       | lock.cc       |         153 |
| Table lock                   | 0.00000400 | mysql_lock_tables       | lock.cc       |         162 |
| init                         | 0.00001600 | mysql_select            | sql_select.cc |        2073 |
| optimizing                   | 0.00005675 | optimize                | sql_select.cc |         617 |
| statistics                   | 0.00001250 | optimize                | sql_select.cc |         773 |
| preparing                    | 0.00005175 | optimize                | sql_select.cc |         783 |
| Creating tmp table           | 0.00001275 | optimize                | sql_select.cc |        1206 |
| executing                    | 0.00006025 | exec                    | sql_select.cc |        1407 |
| Copying to tmp table         | 0.00000400 | exec                    | sql_select.cc |        1547 |
| converting HEAP to MyISAM    | 0.04820900 | create_myisam_from_heap | sql_select.cc |        9914 |
| Copying to tmp table on disk | 0.04049075 | create_myisam_from_heap | sql_select.cc |        9968 |
| Sending data                 | 1.29302000 | exec                    | sql_select.cc |        1925 |
| end                          | 0.09398425 | mysql_select            | sql_select.cc |        2118 |
| removing tmp table           | 0.00004975 | free_tmp_table          | sql_select.cc |        9856 |
| end                          | 0.00089125 | free_tmp_table          | sql_select.cc |        9884 |
| query end                    | 0.00001850 | mysql_execute_command   | sql_parse.cc  |        5085 |
| freeing items                | 0.00000825 | mysql_parse             | sql_parse.cc  |        5973 |
| closing tables               | 0.00003425 | dispatch_command        | sql_parse.cc  |        2120 |
| logging slow query           | 0.00001325 | log_slow_statement      | sql_parse.cc  |        2178 |
| cleaning up                  | 0.00000675 | dispatch_command        | sql_parse.cc  |        2143 |
+------------------------------+------------+-------------------------+---------------+-------------+
21 rows in set (0.00 sec)

    Looking at the lines helped to indicate that the temporary table was being flushed to disk, indicating we need to Add SET SESSION tmp_table_size=20*1024*1024;

    mysql> show profile source for query 18;
+----------------------+------------+-----------------------+---------------+-------------+
| Status               | Duration   | Source_function       | Source_file   | Source_line |
+----------------------+------------+-----------------------+---------------+-------------+
| Opening tables       | 0.00006050 | open_tables           | sql_base.cc   |        2106 |
| System lock          | 0.00001250 | mysql_lock_tables     | lock.cc       |         153 |
| Table lock           | 0.00000400 | mysql_lock_tables     | lock.cc       |         162 |
| init                 | 0.00000775 | mysql_select          | sql_select.cc |        2073 |
| optimizing           | 0.00005475 | optimize              | sql_select.cc |         617 |
| statistics           | 0.00001225 | optimize              | sql_select.cc |         773 |
| preparing            | 0.00005075 | optimize              | sql_select.cc |         783 |
| Creating tmp table   | 0.00001350 | optimize              | sql_select.cc |        1206 |
| executing            | 0.00006125 | exec                  | sql_select.cc |        1407 |
| Copying to tmp table | 0.00000375 | exec                  | sql_select.cc |        1547 |
| Sending data         | 0.29110925 | exec                  | sql_select.cc |        1925 |
| end                  | 0.08023800 | mysql_select          | sql_select.cc |        2118 |
| removing tmp table   | 0.00001525 | free_tmp_table        | sql_select.cc |        9856 |
| end                  | 0.05971400 | free_tmp_table        | sql_select.cc |        9884 |
| query end            | 0.00001925 | mysql_execute_command | sql_parse.cc  |        5085 |
| freeing items        | 0.00000425 | mysql_parse           | sql_parse.cc  |        5973 |
| closing tables       | 0.00004625 | dispatch_command      | sql_parse.cc  |        2120 |
| logging slow query   | 0.00000800 | log_slow_statement    | sql_parse.cc  |        2178 |
| cleaning up          | 0.00000300 | dispatch_command      | sql_parse.cc  |        2143 |
+----------------------+------------+-----------------------+---------------+-------------+
19 rows in set (0.00 sec)

    Google's worse nightmare

    by

    Today while waiting at the airport, I took a look at the news stand, and right there on the cover of Fast Company were two words Google, and Wikipedia. Given Wikipedia is a poster boy of MySQL it was an immediate purchase just to see what was being said.

    So the title of the cover was Google’s worse nightmare – Wikipedia’s Jimmy Wales has his sights set on the search business.

    Now, often I use Wikipedia to search for things directly rather then using Google. I’ve found it usually to be more accurate, particular on topics I know it will contain. References to search users being disappointed, Google and Yahoo tied with a 2.3 of 5 in user satisfaction hits about home for me as week, and that’s exactly the ideas behind www.wikia.com.

    The article states “Google doesn’t have an effective method of locking in its customers the way earlier info-tech leaders did”. Well I’d agree in relation to searching, but Google is rapidly releasing new products, new features and acquiring good ideas. It has the wealth (money and gene pool) to make an impact.

    Some more on www.wikia.com — Wikia offers free MediaWiki hosting for your community to build a free content wiki-based website. Find out why you should use Wikia and request a new wiki in any language or see our list of wikis to visit an existing one.

    Today, it has 69 categories, I’m sure tomorrow it will be more. today’s feature page is The Marvel Database, others like Wookieepedia – The Star Wars encyclopedia and 100’s of entries alone in the Games Category make it something to look at one of day’s when I have free time.

    And best of all it runs the LAMP Stack. Linux, Apache, MySQL, PHP.

    Get behind a new exciting site

    by

    As I write this blog I have over 90 draft blog posts. That’s 9-0. Why do I have so many posts? The main reason is I want to say something, and I’ve either not completed it, or researched it sufficiently to consider the entry complete.

    This frustrates me as sometimes I just want to get the word out on something, or of my opinion, or of something great I’ve discovered. I do it for me, I don’t really care if anybody actually reads my stuff, but I’m surprised sometimes when I get comments how people actually get to see my blog.

    JotThat is a surprisingly simple yet brilliant idea. It’s quite simply a site for making Jots, making quick notes, making a passing comment, noting a thought, something you want to either remember or something you want to say in a simple Jot form.

    What makes JotThat in my eyes? Well it’s simple, and I strive for simple. It’s extremely easy to use. It’s built on MySQL, so that gains my attention. It’s something just a little different from everything you see each day.

    I especially like the new feature of being able to email your Jots to your account. I was at the train station tonight, then later at dinner with some great input from somebody. I wanted to write it down (I forget things a lot more these days), so instead of adding it to notes in my PDA, I simply emailed it to my JotThat account. Easy as!

    The site is still in early stages, but please get behind a project. I always like to get referrals from people on everything from websites, products, even services like a good dentist. I recommend you check this one out, as well as supporting the MySQL open source community.

    MySQL LOAD DATA Trick

    by

    I leaned a new trick today with LOAD DATA INFILE. I’m migrating some data from an external source, and the Date Format is not the MySQL required YYYY-MM-DD, it was DD-MMM-YY. So how do you load this into a Date Field.


    $ echo "02-FEB-07" > /tmp/t1.psv
    $ mysql -umysql
    USE test;
    DROP TABLE IF EXISTS t1;
    CREATE TABLE t1(d1 DATE);
    # echo "02-FEB-07" > /tmp/t1.psv
    LOAD DATA LOCAL INFILE '/tmp/t1.psv'
    INTO TABLE t1 (@var1)
    SET d1=STR_TO_DATE(@var1,'%d-%M-%y');
    SELECT * FROM t1;
    EXIT

    The trick is to bind the appropriate column within the file being loaded to a variable, @var1 in my example and use the SET syntax to perform a function on the variable. Rather cool.

    A good tip to know.

    That missing INNODB STATUS

    by

    On Thursday I saw something I’d not seen before. An Empty Innodb Status. Now given the amount of output normally shown it was certainly a first. And it looked like:

    mysql> SHOW ENGINE INNODB STATUS;
+--------+------+--------+
| Type   | Name | Status |
+--------+------+--------+
| InnoDB |      |        |
+--------+------+--------+
1 row in set (0.03 sec)

    To answer some of the most obvious questions.

    • Yes it was a working existing MySQL instance, with InnoDB correctly configured. Indeed we had been benchmarking for several hours.
    • MySQL Server was running, indeed a command selecting data from the mysql schema worked just fine after seeing this (All other tables were Innodb).
    • Absolutely nothing in the host MySQL error log. (This was the second most disappointing aspect)
    • The Process List showed two queries that had been running for some time, everything was taking  ; 1 second. (This was the most disappointing)

    So the problem is, MySQL seems to effectively hung when dealing with queries solely in InnoDB tables. Closer investigation found that another application process had filled the /tmp file system. Reclaiming space didn’t cause MySQL and InnoDB to start operating. Even a shutdown of MySQL failed, with mysqld having to be killed manually

    For those super inquisitive the version was 5.1.16-ndb-6.2.0-log, and yes it is a Cluster release. I’ve yet to test the problem on a normal 5.1 version and log a bug appropriately if it exists.

    I suspect in our benchmark we definitely need to include some timeout handling, so the queries would fail (they were both UPDATES), but it did have the customer asking why, do which there was no answer.