Month: February 2013

A simple way to migrate Redmine?


Redmine_login_pageFor migration (or DB update) of my Redmine instance, I have performed the steps from my previous article twice by now.

But, this time, I spent 2 days of annoyance by never-before-seen errors from the rake command, while performing the exact same steps. That’s when I gave up trying to research the millions of errors on Google, and decided to adopt a new way.

This time, I performed the below given steps:

1. I installed the exact same version of the Bitnami Stack that I had earlier (with the Installation directory also having the same name and path as before),

2. Stopped the Stack Services of the current instance through the shortcut.

3. Then, I replaced the contents (all the folders & the files) of the entire installation directory with the ones in my previous Stack directory (I had the whole installation directory of my previous stack saved as backup)

4. Executed the following commands –

cd <installdir>

serviceinstall.bat INSTALL

5. Restarted the Stack services through shortcut

And that was it! It all seemed to work fine.

According to the article in Bitnami’s blog, this seems to be a valid way to do it. But, I’m still not sure why any one would perform all the other steps if it were that simple.

What do you think?

Facebook script error affected entire world wide web


FB error

This article is about a recent bug that occurred in Facebook and affected most of the websites in the world wide web.

Many websites, including the major and hugely popular ones like MSNBC.com, CNN,  Pinterest, ESPN, TED, HBO, WordPress, Yahoo, and The Washington Post, were brought down by an error in a Facebook script on February 7, 2013. Upon visiting the websites, users were redirected to an error page inside of the Facebook website.

Most sites use this small Facebook script to allow visitors to “like” and “share” their products and news on Facebook. So, although Facebook quickly fixed the issue, millions of users were affected by it.

Now, imagine a malevolent hacker somehow finding a way to inject their code into legitimate websites in this manner, and having his/her script executed in millions of machines almost instantaneously. Sends shivers down the spine just to think how vulnerable our internet really is.

Here’s a video of the error occurring in real-time:

Search in SQL for a value containing a ‘ character


So, you are stuck with a problem…

You need to find User names that are stored in the DB Users table, and that contain the apostrophe character. (eg. Susan D’Souza)

How do you go about it?

You know the LIKE keyword has to be used somewhere. But, when you add the apostrophe character in the LIKE criteria, the query gives an error (as displayed below) on execution.
SQL LIKE query with apostrophe

Error for SQL LIKE query with apostrophe

It took a while for my colleague and I to find the resolution to this, but thanks to the world wide web, we did find it. 😀

And now I am writing it down here for the benefit of any one else who stumbles across this entry while searching online for the solution. (and of course, for my future reference)

And it’s a very simple solution –
Instead of just one apostrophe character, write 2 of them consecutively in the LIKE criteria.

An Example is given below-

>> SELECT * FROM Users where UserName like ‘%D”Souza%’

The above query will give you the list of all the users that have “D’Souza” in their name.

Happy Querying and see you soon… 🙂

Ordering of Strings according to numbers contained in them


This is an error that is more common than you would think.

Take an instance – There is a column in the Database table such as a Profile ID, and the developer thinks of sorting the records according to the Profile ID in either an ascending, or a descending order. eg. Sorting records by descending Profile ID to show the latest added records first.

What happens is that the Profile Id is alphanumeric, and default sorting of such records is not exactly as one would expect.

Below is the description of a recent bug I raised. You will understand what I’ve been trying to say by reading it.

Bug Description – “The ‘Top Deals in your City’ section of Home page is required to show the latest entered bike listings.
However, Latest Listings were not being displayed as expected. Issue is as  explained below:

Listings were being Ordered by ProfileID, and not by EntryDate.
Hence, a listing with ProfileID ‘S27’ that was entered on ‘2012-08-27 20:24:26.067’ was considered newer than a listing with ProfileID ‘S237’ that was entered on ‘2013-02-05 11:13:27.637’

Strings are ordered as ascending/descending in a way different from the ordering of integers.
Hence, while ordering, ‘S27’ was considered to be greater than ‘S237’ ”

Have I succeeded in explaining this to you yet? Let me try again..

You have the following values:

A1

A2

A10

A108

A20

A3

You want to order them in the ascending order. What would you expect the result to be? I’m sure everyone would expect it to be as below;

A1

A2

A3

A10

A20

A108

But, the default sort functions in almost every programming language would return the below result. The records are sorted in ASCII order, and not in Alphabetical order.

A1

A10

A108

A2

A20

A3

What can we do to resolve this problem? Let’s see…

1. The first and most simple solution would be to not use the alpha-numeric column for sorting the records.

Instead, one could use a Date column to sort records (as mentioned in my bug description above), or one could use an ID column that contains only numbers and is meant for sorting the records.

Proper planning of Database architecture could help prevent this problem from arising.

2. If the only way to sort records is to use the alpha-numeric column, then one can use “Natural Sorting”. Following are some good links that would help you understand this subject more.

The Alphanum Algorithm

Sorting for Humans : Natural Sort Order

Natural Sorting in C#

Compact Python Human Sort