In this chapter we discuss timeouts which can lead to
"MySQL server has gone away" and "Lost
connection to MySQL server" errors.
Extract here is short, because there are a lot of code quotes which I can not properly format here.
Chapter 9. Misterious vanishing of the server.
Often this looks like:
$php phpconf2009_3.php
string(26) "MySQL server has gone away"
Code:
Rest of the chapter is here
As olap4j heads towards release 1.0, there are
further signs that it is coming of age, in the form of drivers
for the Palo MOLAP engine and SAP BW.
A few days ago Paul Stoellberger announced that olap4j's XMLA driver could
connect to SAP BW, and posted pictures of PAT, PRD and PDI to
prove it.
And just a week later, Jedox CEO Kristian Raue writes about how to connect to Palo.
His post includes a blessedly short Java program …
(Reposted from the HailDB Blog. See also the announcement on the Drizzle Blog.)
We’ve made our first HailDB release! We’ve decided to make this a
very conservative release. Fixing some minor bugs, getting a lot
of compiler warnings fixed and start to make the name change in
the source from Embedded InnoDB to HailDB.
Migrating your software to use HailDB is really simple. In fact, for this release, it shouldn’t take more than 5 minutes.
Highlights of this release:
As described in the prior post, the shared-disk performance
dilemma is simple:
1. If each node stores/processes data in memory, versus disk, it
is much faster.
2. Each node must expose the most recent data to the other nodes,
so those other nodes are not using old data.
In other words, #1 above says flush data to disk VERY
INFREQUENTLY for better performance, while #2 says flush
everything to disk IMMEDIATELY for data consistency.
Oracle recognized this dilemma when they built Oracle Parallel
Server (OPS), the precursor to Oracle Real Application Cluster
(RAC). In order to address the problem, Oracle developed Cache
Fusion.
Cache fusion is a peer-based shared cache. Each node works with a
certain set of data in its local cache, until another node needs
that data. When one node …
So you thought that just because MySQL Cluster 7.1 is GA on
Windows that NDB API was available and you could just download
the MySQL Cluster 7.1 binary for Windows and start hacking the
NDB API. Nope. But fear not, there is help!
And before I go on with that: For all you *ix users here, who
claim that no one in their right mind would use MySQL Cluster on
Windows, let me tell you that you may well be right! But, and
this may be a not so PC statement: Although I like and use *ix
(I've actually been using *ix for close to 30 years) as a server
platform, when it comes to the desktop, I think Windows still has
the edge. There is just too many options on, say Linux, too
little coherence and too little commonality between applications.
And it sure is getting better, very much so, but there is still
some way to go.
So then, when we have my reasons for me doing what I am currently
doing behind our backs, what I am trying to …
InnoDB is known to have crash-recovery capabilities and thus is called a crash safe storage engine (in contrary to MyISAM). Never the less under certain circumstances it seems like InnoDB pages can get corrupt during a crash and then a manual crash-recovery is needed.
Oracle/MySQL blames in such cases the Operating System, the I/O system or the hardware. What we have seen is that such incidents occur more often on Windows systems and when people are running their databases in a virtualized environment (VMWare). Because of the small number of cases we are aware of, this may not be representative.
One of our customers did systematic crash tests with InnoDB in a virtual machine and got the problem below (MySQL error log):
InnoDB: Log scan progressed past the checkpoint lsn 0 548857890 InnoDB: Database was not shut down normally! InnoDB: Starting crash recovery. InnoDB: Reading tablespace information from the .ibd files... InnoDB: …[Read more]
On Wednesday 25 August, Johan Anderson and Mat keep will be presenting a free webinar on the best practices for deploying MySQL Cluster. If you’d like to attend then just register here.
Johan has years of MySQL Cluster professional services experience – and so if you’re interested in deploying a product ready MySQL Cluster database then this is a must-view session. Even if you can’t make it live, register anyway and you’ll be sent a link to the recording and charts afterwards.
Content
An invaluable session for those who are about to, or who already have, deployed MySQL Cluster. Delivered by the lead MySQL Cluster professional services consultant in Oracle, this session will present best practices on deploying MySQL Cluster in order to accelerate time to service with the highest levels of availability …
[Read more]This tip is several months late but here goes anyway.
In my opinion, when you have an environment where you're using multiple MySQL storage engines (using the right tool for the job and all that jazz), there is nothing more annoying than to have tables created or altered into a storage engine that you did not request. The default behaviour of MySQL is to use the default engine if the requested
You take a look at someone’s MySQL (or MariaDB) data directory, and see
mysql
foo
bar -> foo
Good luck!
OUTER JOIN queries in SQL are susceptible to two very subtle bugs that I’ve observed a number of times in the real world. Daniel and I have been hammering out ways to automatically detect queries that suffer from these bugs, in a relatively new Maatkit tool called mk-query-advisor. It’s part of our series of advisor tools for MySQL. I wrote a blog post about it a while ago. Automated analysis of bad query patterns is a good thing to write tools to do, because catching buggy queries is hard work if you do it manually.