Grrrr… nothing like a MySql bug to really make your day.

I had need to generate a sum for a column of duration values with the type of TIME.  Orginally I used this as part of my query:

sum(call_duration) as totalhours

Turns out this does not work properly and has apparently been a problem since 2005!

http://bugs.mysql.com/bug.php?id=12108

From reading the comments, there appears to be some argument as to the validity of the bug.  For what it’s worth, I found that the problem is more pronounced with more results.  I found that it was non-existant (that is that the sum returned the correct value) with result sets with only a few rows.   The problem seemed to get more severe based on more rows in the results.  In my case, a result set with about 2000 rows in it had an error of on the order of three hours.

The work around is to modify the query slightly:

sum(TIME_TO_SEC(crf_call_duration)) as totalhours

This converts the time to essentially an integer which is then properly handled by the sum.  You can then either work with the result as a count of seconds, or use the function SEC_TO_TIME to convert it back to a TIME value.

I hope this helps someone else.  It cost me a number of hours…

One of the things I needed to do was get an FTP installation working so I could send stuff to the board.  Apt-get did a fantastic job of getting and installing Proftpd and I had the daemon up and running in like five minutes.  So far so good.  Until I tried to log in.

Nada.  Damn.

Endless searches and configuration changes and log checks did me no good.  For a while in fact, I wasn’t even getting a log at all.  Turns out the default setup doesn’t include logging.  They don’t do a good job of telling you that either.  My log setup is:

# Logging formats
LogFormat default “%h %l %u %t \”%r\” %s %b”
LogFormat auth “%v [%P] %h %t \”%r\” %s”
LogFormat write “%h %l %u %t \”%r\” %s %b”

# activate logging

# every login
ExtendedLog /var/log/ftp_auth.log AUTH auth

# file/dir access
ExtendedLog /var/log/ftp_access.log WRITE,READ write

# forr paranoid (big logfiles!)
ExtendedLog /var/log/ftp_paranoid.log ALL default

Yes I know it’s probably overkill, but this will be for low volume use, so I don’t care if the logs have big entries.  There won’t be many.  That fixed my logging problem.  It didn’t get me logged in though.  After what was probably endless hours of searching, I found this post:

http://raetsel.wordpress.com/2007/03/28/proftpd-shells-and-nobody/

Turns out that my problem was the “gotcha” he mentions first.  If you are using actual system users for FTP (as opposed to virtual users) you need to be sure the shell is set properly.  Apparently when you adduser it isn’t.  It requires use of chsh to set to a valid shell in order to log in.  I set my user to /bin/bash and voila!  If you’re not sure what the shell is for the user you want to use, check out /etc/passwd.  Its the last field in the entry.  If there is a setting there (unlike mine which was blank) and it still doesn’t work, make sure that the shell that is assigned is actually a valid one (my first attempt was bin/bash not /bin/bash which didn’t work either).

If you have assigned a shell that is proper then you can next check /etc/shells to make sure that the one you’ve assigned is a valid login shell.  I didn’t need to.  Your mileage may vary (YMMV).  If this helps you, please feel free to leave a comment to that effect.

I hate computers.  Never do what you want them to do, only what you tell them to do.

I’ve decided I’m going to start adding some other geeky stuff here too.  I’ve been using WordPress lately as a content management system (CMS) for several of my websites, and all I can say is, I’m in love!  I’ve also found a fabulous plugin for images for WordPress called Nextgen Gallery.  I’ve been using both through several versions now and am currently on WordPress 2.7 and Nexten Gallery 1.0.2.

In case you’re interested in WordPress, you can find it here, and Nextgen Gallery is here.  Lots of examples at the Nextgen site as well.

One of the small changes I’d like made in Nextgen Gallery is the way the navigation through images is done if you use pagination.  Currently if you set max images to something other than 0, it limits the number of thumbnails displayed to that number.  I happen to like 4 because it doesn’t crowd the posts with a million thumbnails.  When you click on a thumbnail, it opens a Thickbox with the image.  The problem is, the Thickbox includes previous and next links to move through the images, but they only navigate through the limited number of images on that page and not the whole gallery.

I want them to navigate through the whole gallery so you don’t have to switch back and forth and navigate through both the pages AND the images.  Unfortunately this isn’t a feature that’s included.  In a previous version of Nextgen, 0.99, I followed some online instructions to modify the plugin to get it to do what I wanted.  If you’re using that version, you can find those instructions here.  Unfortuantely, they don’t work for the newest version (1.0.2) because of significant changes to the applicable routines.  So… I got to work.  To make a long story a bit shorter, here are the modification instructions:

// remove the element if we didn't start at the beginning
if ($start > 0 ) array_splice($picturelist, 0, $start);

// return the list of images we need
array_splice($picturelist, $maxElement);

//Don't modify the array.  We now want to pass all of the picture list
//to the output... but not all are visible as thumbnails.
//TODO:  make a configuration option to select or deselect this
//behavior

foreach ($picturelist as $index => $value)
{
if (($index < $start) || ($index >= ($start + $maxElement)))
  $picturelist[$index]->imageHidden = 1;  //if out of range,
                                          //hide image
else
  $picturelist[$index]->imageHidden = 0;  //otherwise, show it
		}

var $href = '';		// A href link code

var $imageHidden = 0;  	// show or not show thumbnail

<!-- Thumbnails -->
<?php foreach ($images as $image) : ?>

<div id="ngg-image-<?php echo $image->pid ?>"
class="ngg-gallery-thumbnail-box">

<div id="ngg-image-<?php echo $image->pid ?>"
class="ngg-gallery-thumbnail-box"
<?php
  if ( $image->imageHidden == 1 )
  {
    echo " style='display: none' ";
  }
?>
>