I believe I’m nearly done with the SHOW EXPLAIN feature. The idea is that if you’ve got some long-running query $LONG_QUERY running in connection $LONG_QUERY_CONN, you should be able to create another connection, run SHOW EXPLAIN FOR $LONG_QUERY_CONN and see what query plan is being used to run the $LONG_QUERY.

How is this different from just running explain $LONG_QUERY? First, you don’t need to replicate the exact environment that $LONG_QUERY was run in: you don’t need to figure out what values it had for @@optimizer_switch and other settings, what were the contents of its temporary tables, if any, what did InnoDB told the optimizer about the table statistics, etc.

Another, indirect benefit is that we will now be able to produce query’s EXPLAIN at arbitrary point in time, which should make it possible to …

It’s been released. Use this with NIST::NVD 1.00.00 and you will be able to perform immediate look-ups of CVE and CWE data given a CPE URN. For instance:

cjac@foxtrot:/usr/src/git/f5/NIST-NVD-Store-SQLite3$ perl Makefile.PL ; make ; make test ; cjac@foxtrot:/usr/src/git/f5/NIST-NVD-Store-SQLite3$ perl -MNIST::NVD::Query -MData::Dumper -e '
$q = NIST::NVD::Query->new(store    => q{SQLite3},database => q{t/data/nvdcve-2.0.db});
$cve_list = $q->cve_for_cpe( cpe => q{cpe:/a:microsoft:ie:7.0.5730.11} );
print Data::Dumper::Dumper { cve_list => $cve_list, first_cvss => $q->cve( cve_id => $cve_list->[0] )->{q{vuln:cvss}} }
'
$VAR1 = {
          'cve_list' => [
                          'CVE-2002-2435',
                          'CVE-2010-5071'
                        ],
          'first_cvss' => {
                            'cvss:base_metrics' => { …

When you use SHOW VARIABLES LIKE “have_%” to see whether a particular feature is enabled, you will note the value of NO for some, and DISABLED for others. These values are not intrinsically clear for the casual onlooker, and often cause confusion. Typically, this happens with SSL and InnoDB. So, here is a quick clarification!

• NO means that the feature was not enabled (or was actively disabled) in the build. This means the code and any required libraries are not present in the binary.
• DISABLED means that the feature is built in and capable of working in the binary, but is disabled due to relevant my.cnf settings.
• YES means the feature is available, and configured in my.cnf.

SSL tends to show up as DISABLED, until you configure the appropriate settings to use it …

Sheeri K. Cabral at the Mozilla Foundation wrote about an issue with the June 30th 2012 leap second affecting at least MySQL, Java and Minecraft servers. It now appears that the underlying cause is a Linux kernel bug, as noted by John Stultz (IBM) on the Linux Kernel mailing list, and the team Sheeri is part of deserves due credit for doing awesome pattern recognition and being the first to bring it to public attention, enabling people to quickly correlate their own experience with that of others and finding a practical solution as well as helping figure out the cause.

Sheeri’s original post MySQL and the Leap Second, High CPU and the Fix describes how MySQL servers would suddenly exhibit high CPU usage during a period of low load. …

I’ve been working on a data archival project over the last couple weeks and thought it would be interesting to discuss something a bit counter-intuitive. Absolutes are never true, but when getting rid of data, it’s usually more efficient to insert the data being kept into a new table rather than deleting the old data from the existing table.

Here is our example table from the IMDB database.

mysql> show create table title\G
*************************** 1. row ***************************
       Table: title
Create Table: CREATE TABLE `title` (
  `id` int(11) NOT NULL AUTO_INCREMENT,
  `title` text NOT NULL,
  `imdb_index` varchar(12) DEFAULT NULL,
  `kind_id` int(11) NOT NULL,
  `production_year` int(11) DEFAULT NULL,
  `imdb_id` int(11) DEFAULT NULL,
  `phonetic_code` varchar(5) DEFAULT NULL,
  `episode_of_id` int(11) DEFAULT NULL,
  `season_nr` int(11) …

” There is a variety of services possible via IPTV. Starting with live/linear TV and Video on Demand (VoD) over interactive broadcast related apps, like shopping or advertisement, up to social TV apps where communities of users have shared TV experience”– Stefan Arbanowski. The research center Fraunhofer FOKUS (Fraunhofer Institute for Open Communication Systems) in [...]

Oracle OpenWorld 2012

I’m lucky enough to be involved in a number of sessions across Oracle OpenWorld as well as the (new for this year) MySQL Connect session that precedes it. MySQL Connect runs on Saturday 29th and Sunday 30th September and the Oracle OpenWorld on through Thursday October 4th.

The sessions I’ll be involved with are:

• MySQL Cluster – From Zero to One Billion in Five Easy Steps: Of course it takes more than five steps to scale to more than one billion queries per minute, …

Come join the San Diego MySQL Users group on August 2nd for a look at MySQL 5.6 and help make some pizza disappear. The presentation will start at 7PM and all are welcome.

Oracle Office
9515 Towne Center Drive
San Diego, CA 92121

As I reported via Twitter late last week, we encountered an issue that got some of our mail delivery delayed by about a day and a half. I’ll explain more about what happened as I believe in openness on these matters, and also the experience has educational content for others.

Our mail server doesn’t have direct external interaction, it’s shielded by two relays that handle both the inbound MX and the outbound queue. This setup works remarkably well in terms of exposure to spam and other malicious activity. As previously discussed, it appears that it’s more difficult to make mail server infra more resilient without expending lots more time/effort and infrastructure expenditure. Just because of the way the common tools for mail delivery and imap are built, having two or more of each in a semi-active setup gets quite complex. Complexity is in itself a risk so it has to be considered in relation to the costs and risks of the …

A coworker came to me with a perplexing issue. He wanted to know why these two queries were not returning the same results:

mysql> SELECT COUNT(*) 
    -> FROM parent
    -> WHERE id NOT IN (SELECT parent_id FROM child);
+----------+
| count(*) |
+----------+
|        0 |
+----------+
1 row in set (7.84 sec)

mysql> SELECT COUNT(*)
    -> FROM parent p
    -> WHERE NOT EXISTS(SELECT 1 
    ->                  FROM child c
    ->                  WHERE p.id = c.parent_id);
+----------+
| count(*) |
+----------+
|     5575 |
+----------+
1 row in set (2.95 sec)

At first (and second, and third) glance these two queries look identical. It obviously is an exclusion join and because the MySQL optimizer is what it is, I decided to rewrite it as a LEFT JOIN to see what results came back:

mysql> SELECT …