The freshly released MySQL 8.0 includes a data dictionary, which makes MySQL much more reliable. Thanks to this features, we don't have any '.frm' files, and querying the information_schema is 30x to 100x faster than previous versions.

One drawback of the implementation is that the data dictionary tables are hidden by design.

While the reason is fully understandable (they don't want to commit on an interface that may change in the future) many curious users are disappointed, because openness is the basis of good understanding and feedback.

The problem to access the dictionary tables can be split in three parts:

• Finding the list of tables; …

I was talking with a client and the topic of password crypting came up. From my background as a C coder, I have a few criteria to regard a mechanism to be safe. In this case we’ll just discuss things from the perspective of secure storage, and validation in an application.

1. use a digital fingerprint algorithm, not a hash or CRC. A hash is by nature lossy (generates evenly distributed duplicates) and a CRC is intended to identify bit errors in transmitted data, not compare potentially different data.
2. Store/use all of the fingerprint, not just part (otherwise it’s lossy again).
3. SHA1 and its siblings are not ideal for this purpose, but ok. MD5 and that family of “message digests” has been proven flawed long ago, they can be “freaked” to create a desired outcome. Thus, it is possible to …

Recently, someone emailed me:I have a requirement in MYSQL as follows:
we have a table EMP and we have to restrict the users not delete employees with DEPT_ID = 10. If user executes a DELETE statement without giving any WHERE condition all the rows should be deleted except those with DEPT_ID = 10.

We are trying to write a BEFORE DELETE trigger but we are not able to get this functionality.

I have seen your blog where you explained about Using an UDF to Raise Errors from inside MySQL Procedures and/or Triggers. Will it helps me to get this functionality? Could you suggest if we have any other alternatives to do this as well?Frankly, I usually refer people that write me these things to a public forum, but this time I felt like …

As per amorize.com MySQL.com was hacked and quote “infecting visitors with malware” .. true or false? …

More reading at krebsonsecurity.com too.

So… Baron blogged about wanting higher precision timers from the mysql binary and that running sed on the binary wasn’t cutting it. However… I am not one to give up that easily!

This is what LD_PRELOAD was made for! Evil nasty hacks to make your life easier!

By looking at the mysql.cc source code, I can easily work out how this works… I just have to override two calls! They being sysconf() (we fake how many ticks per second there are) and times() (let’s return a much higher precision number).

Combined with the sed hack on the binary to change the sprintf call to print out the higher precision number, we have:

mysql> select count(*) from t1;
+----------+
| count(*) |
+----------+
|   710720 |
+----------+
1 row in set (1.080110 sec)

Get it from my junkcode: …

BackgroundNormally, I would use a comment. The first thing I would think is
CREATE PROCEDURE p1(i int) select "hello" /* This is my text */
But most client libraries will strip it.
There was a …

You have a huge mysql table - maybe 100 GB. And you need to run alter on it - to either add an index, drop an index, add a column or drop a column. If you run the simple mysql "alter table" command, you will end up spending ages to bring the table back into production.

Here is a simple hack to get the thing done. The benefit of the hack is that the alter runs quite fast. But since this is a hack

A while ago I wrote about MySQL 5.1 information schema plug-ins.

At the time, I wrote a plug-in to report the contents of the query cache, but for all kinds of reasons, I never found the time to write a decent article about it, nor to release the code.

I am not sure if I'll ever find the time to write that article, but I just tidied up the code, and installed it in a new MySQL 5.1.26-rc server. It seems to work there, so I put the code up on the web.

Inside the source file, there's instructions to build and deploy it. If all goes well, you can do …

Few days back, Baron re-introduced MySQL's command line pager command and described some cool tricks with maatkit's mk-visual-explain (one of my favorite tools). Soon after reading it, I wished if it was possible to describe regex based (on query) paging.

I have written a small hack, christened mysmartpager, that can actually do regex based paging for you.

The idea is simple, write a relay that will redirect the output based on to the desired pager. The problem was complex, there was no direct way of getting to know the original query. There are a couple of indirect ways of doing so, but of course with hurdles:

• Run mysql client with --xml option: This will print the output of each command in xml and the command itself is included in the xml. The downside was not many pagers (including …

Are you getting fed up yet with my posts on calculating percentiles? Well, I'm sorry but I'm not quite finished.

Here's a simple, fast method to calculate the specified number of quantiles:

-- set the number of quantiles, for exmple:
--   quartiles: 4
--   deciles: 10
--   percentiles: 100

SET @quantiles:=4;  -- select quartiles

-- calculate all quantiles
-- 
--
SELECT     amount                     AS metric
,          @n DIV (@c DIV @quantiles) AS quantile
,          @n                         AS N
FROM       sakila.payment
CROSS JOIN (
            SELECT @n:=0                           -- rownumber
            ,      @c:=COUNT(*) …