A friend of mine called me today, asking for advice on a baffling error.
He has just finished upgrading a database server from 4.1.20 to 5.0.45but, when attempting a backup to all databases with mysqldump, he gets a discomforting message:

mysqldump: Got error: 1044:
Access denied for user 'root'@'localhost' to database 'information_schema'
when using LOCK TABLES

Of course, the error is doubly strange.

• First, because mysqldump is not supposed to attempt dumping the information schema. I know for sure, since I had to write a special script to dump the I_S when I really needed to export its data.
• Second, because there was actually …

I start to see applications being built utilizing VIEWs functionality which appeared in MySQL 5.0 and quite frequently VIEWs are used to help in writing the queries - to keep queries simple without really thinking how it affects server performance.

Even worse than that - looking at the short table which just gets single row from the table by the key we think this is simple query, while can be real monster instead with complexity hidden away in VIEW definition.

Just another day I worked on optimizing application which uses VIEWs and was looking at the long running query which just joined 2 tables... I ran EXPLAIN for it and got 200 of rows in the result set just for explain due to several layers of cascaded views built on top of one another so it is easy to write the queries, some of them it turn used subqueries subselects and derived tables.

It is also very dangerous if you assume MySQL would optimize your VIEWs same way …

Yesterday I ran into the article which sheds some light on FaceBook search implementation. As we're recently a lot into search having implemented a bunch of search projects ourselves and helped number a of customers with their full text search needs I decided to post my thoughts on this matter.

First I was surprised article talks about just 1TB of data. I knew FaceBook has much more content than that. Though it seems the article only speaks about searching user profiles and similar global objects not full database of posts and comments. At FaceBook scale it is easy to fit 1TB in distributed memory which makes a lot of things easier.

Second this I was surprised about is about writing crawler for a site.... why would you do that if there is already information in the database which is much faster to extract. Even if data needs to be aggregated from …

my girlfriend hates blogs :(

Yes! We did it! Just before I went to bed at 3:40AM (heh ), I noticed, that someone submitted new video to BTV. I’ve approved it instantly and then noticed a following information in the top part of the site: “We have 1000 videos / 569+ hours of high-quality content!” So, we broke trough 1k videos barrier! And we’ll try to do 2k videos before the end of this year, we have some new features in closed beta testing which would greatly increase number of submitted videos each day.

Thanks to all our users for their contributions and support! …

MySQL AB’s recent changes to the Community/Enterprise split have made people go as far as calling the split a failure. I don’t think it’s working well either, but it could be fixed. Here’s what I think would make Enterprise a compelling offer. I’d recommend Enterprise if I could If the MySQL Enterprise Server were a good thing, I’d recommend it to my consulting clients. I’d suggest we start using it at my employer, too.

Friends are pointing me to the article saying SpyLOG, the startup which I co-founded back in 1999 was sold the other day to the MasterHost. The amount is not disclosed but it is estimated to be $3M - amount not worth mentioning for USA market but quite decent one for Russian Internet Market.

So I guess after all this project with not easy destiny can be called successful.

It is especially Interesting another month we announced our own startup project ClickAider which operates in related market. This deal reassures us there are money to be earned in the area.

In general looking back to my years spent with SpyLOG (1999-2002) I find them to be stressful but very rewarding in terms of knowledge and experience. We had great Development team with our team members later going to play important roles in projects like …

Tarring and Feathering, 1773

(Credit: Public Domain)

Deja vu. Remember 2002? That's when Red Hat decided to split its code into Red Hat Advanced Server (now Red Hat Enterprise Linux) and Fedora. Howls of protest and endless hand-wringing ensued: How dare Red Hat not give everything away for free?

Enter 2007. MySQL decides to comply with the GNU General Public License and only give its tested, certified Enterprise code to those who pay for the service underlying that code (gasp!). Immediately cries of protest are raised, How dare MySQL not give everything away for free?

Ironically, in this same year of 2007, SugarCRM received universal plaudits (from me, as well) for opening up part of …

A healthy open source project is a little like a chemical reaction and requires three key elements:

1. Users

This sounds funny, but some open source projects forget that they need users. They're written by developers based on their notions of how software "should" be, instead of for users based on what they need. The result is that funny-looking "who came up with this?" kind of a look.

This might make writing the software easier or more enjoyable for the developer, but long term it is foolish. Users are the raw material of an open source project. In one way or the other, they ultimately support the developers, whether by hiring the developers as employees or service providers or providing a pool of potential contributors and developers down the road.

2. Developers

But if there are only users, then an open source project would develop at a glacially slow pace. Projects that …

(define luhn-check
  (lambda (ccn)
    (define csum 0)
    (define num 0)

    (do ((i (string-length ccn) (- i 1)))
      ((<= i 0) (print csum))

      (set! num (string->number (substring ccn (- i 1) i)))
      (if (> (modulo i 2) 0)
                        (begin

                         (set! num ( * 2 num))
                         (if (> num 9) (set! num (- num 9)))))

      (set! csum (+ num csum))
      )))
;; test case
(luhn-check “4561261212345467″)

And here is implemented with MySQL.