lunatechian (lunatech-ian)

A few days back we were trying to optimize a sql query that was using an ORDER BY clause. When we ran an EXPLAIN on the query, we saw that the query was Using filesort and Using temporary. Since this query was run quite frequently, there was a benefit in optimizing this.

I had been under the impression that if your query uses filesort and then has to use temp tables for sorting, you cannot do much to save the query. However, that is not the case. If you have an index on the column being used to do the order by , mysql will use that index for sorting. Of course, there are caveats to this, the most important one being

The key used to fetch the rows is not the same as the one used in the ORDER BY: SELECT * FROM t1 WHERE key2=constant ORDER BY key1;

Hence, if you have a query which requires to be sorted, and it is being run quite frequently, it makes sense to add an index on the column on which you are doing the sort.

This is from a spam I got recently. It had "Viagra" spelled out using table (like an 8x8 display). Interesting

knowing you can still understand output from diff, even though it has been months you touched any code.

I am using a Mac now, and this blog post is brought to you by the same php and lisp scripts that I was using on my linux box. Cheers!

Have you read the man malloc page recently? Did you notice this section there

Recent versions of Linux libc (later than 5.4.23) and GNU libc (2.x) include a malloc implementation which is tunable via environment variables. When MALLOC_CHECK_ is set, a special (less efficient) implementation is used which is designed to be tolerant against simple errors, such as double calls of free() with the same argument, or overruns of a single byte (off-by-one bugs). Not all such errors can be protected against, however, and memory leaks can result. If MALLOC_CHECK_ is set to 0, any detected heap corruption is silently ignored; if set to 1, a diagnostic is printed on stderr; if set to 2, abort() is called immediately. This can be useful because otherwise a crash may happen much later, and the true cause for the problem is then very hard to track down.

So, you can do export MALLOC_CHECK_=1 and malloc will print debugging messages to the stderr.

If you want to check what compile options were used to build the emacs, check the value of the variable system-configuration-options in emacs. i.e. C-h-v system-configuration-options

In my case, it is `—with-x-toolkit=gtk' '—with-xft=yes' '—prefix=/home/rshekhar/fakeroot/'`

Check out SpaceGlow joomla template by Bernard Esterhuyse. It is nice, however, more importantly, it is GPL-ed. I have been checking put a lot of joomla templates for my site, but all the joomla templates that I came across shared an important defect. Even though the template authors mentioned that the template was GPL-ed, they usually had a link to their own sites in the template, along with the request (or order), not to remove that line.

The Spaceglow template is really GPL-ed. This will allow me to hack it up further.