Detach a series of databases in MSSQL

declare CUR cursor for
    SELECT name
    FROM master..sysdatabases
    where name like 'ABC_%'

declare @db varchar(50)
declare @msg varchar(200)

open CUR

fetch next from CUR into @db
while @@FETCH_STATUS = 0
begin
    set @msg = 'detach ' + @db
    raiserror (@msg, 0, 1) with nowait
   
    exec sp_detach_db @db, 'true'
   
    fetch next from CUR into @db
end

close CUR
deallocate CUR


---- Below is batch script to quickly remove disk files. Note you can use multiple wild card match. ----

ECHO OFF

FOR /f "tokens=*" %%i in ('DIR /a:d /b D:\mssql_db\*abc* D:\mssql_db\*xyz*') DO (
    ECHO %%i
    rmdir /s /q "D:\mssql_db\%%i"
)

Hadoop - The Definitive Guide

Hadoop - The Definitive Guide, 3rd edition.

Just got this book over the weekend. Now reading.

The 2nd edition of this book is available here.

Reference:
[1] 15+ Great Books for Hadoop

How jQuery is written from scratch?

This probably helps: http://www.mikedoesweb.com/2012/creating-your-own-javascript-library/

This is a minimum javascript library whose grammar is very similar to jQuery: _('id').function(). It helps to understand how jQuery is written from scratch.

I think I can start writing a javascript library similar to jQuery now :).

Wikipedia management

Wikipedia is a nice open source project. However it may incur a lot of hackers' interests if it is open for edit. Hackers may register large number of spam accounts, create new pages and modify existing pages. This is what's happening to a wikipedia I'm managing right now.

Although quite straightforward, I keep log of these management tips of wikipedia.

The default settings are in wiki/includes/DefaultSettings.php. But changes to settings can be made in wiki/LocalSettings.php, the changes here will override default settings.

1) To change logo, change this line:

$wgLogo = "$wgStylePath/common/images/wiki.png";


2) To disable anonymous user (not logged in) creating new page and editing, add this to the end of LocalSettings:

#
# See: http://www.mediawiki.org/wiki/Manual:User_rights
#

#
# not-logged-in user
#
$wgGroupPermissions['*']['createaccount'] = false; # no new user registration.
//$wgGroupPermissions['*']['read']          = true;      # default is true, so no need to add this statement.
$wgGroupPermissions['*']['edit'] = false;
$wgGroupPermissions['*']['createpage'] = false;

#
# logged-in user. 
# Add this if you want to disable logged-in users from createpage/edit actions.
#
#$wgGroupPermissions['user']['edit'] = false;
#$wgGroupPermissions['user']['createpage'] = false; // true;

#
# sysop
# If you disabled logged-in users actions, you may want to enable sysop's permission here.
#
#$wgGroupPermissions['sysop']['edit'] = true;
#$wgGroupPermissions['sysop']['createpage'] = true;

After you disabled new user's createaccount ability, you will want to manually create new accounts. You can do this by logging in as sysop, and going to "Special pages -> Login / create account".

3) Email setting. Use $wgSMTP to change email setting: either use Pear Mail or PHP Mail.

Refer to the last post "Fix Bluehost wikipedia email problem".

Fix Bluehost wikipedia email problem

I'm managing a website hosted by Bluehost.com.

From CPanel I installed wikipedia. However the email function does not work. It says: "bluehost Mailer returned: Failed to add recipient: [email] … Mailer returned: Unknown error in PHP's mail() function."

I followed instruction at http://www.mediawiki.org/wiki/Manual:$wgSMTP to add email SMTP setting to wiki/LocalSettings.php:

$wgSMTP = array(
 'host'     => "mail.example.com", 
 'IDHost'   => "example.com",      
 'port'     => 26,                 
 'auth'     => true,               
 'username' => "my_user_name",     
 'password' => "my_password"       
);

Still it does not work. I followed Bluehost's email setting page, use either SSL/TLS setting or non-SSL setting. Still it fails.

Finally I tried to find out where $wgSMTP is used: grep -i wgSMTH */*, and found it being used in /wiki/includes/UserMailer.php. It comes down to the function send().  When $wgSMTP is used, it uses Pear Mail; otherwise, it uses PHP Mail. Since I'm using PHP Mail in a personal project on the same server, I tried to check what's different it uses PHP Mail from my use. On line 359 of UserMailer.php, it has this code:

foreach ( $to as $recip ) {

      if ( $safeMode ) {

          $sent = mail( $recip, self::quotedPrintable( $subject ), $body, $headers );

      } else {

          $sent = mail( $recip, self::quotedPrintable( $subject ), $body, $headers, $wgAdditionalMailParams );

      }

}

I print out $headers, it is:

From: CareerAssist Wiki Return-Path: apache@www.careerassist.org Date: Tue, 04 Nov 2014 04:41:29 -0700 Message-ID: X-Mailer: MediaWiki mailer MIME-Version: 1.0 Content-type: text/plain; charset=UTF-8 Content-transfer-encoding: 8bit

Since I'm using the PHP's mail() function in a personal project on the same server and it works well, where I simply use: $headers = "From: [email]";

So I replace the $headers here with this simpler rendition:

foreach ( $to as $recip ) {

      if ( $safeMode ) {

          $sent = mail( $recip, self::quotedPrintable( $subject ), $body, $headers );

      } else {

          $headers = "From: [email]";

          $sent = mail( $recip, self::quotedPrintable( $subject ), $body, $headers, $wgAdditionalMailParams );

      }

}

Then it works! This also shows it takes the 2nd path here ($safeMode is false).

Thus I got wikipedia email working on Bluehost, with this hack into wikipedia's source code.

Mysql - myisam and innodb

Major differences:

innodb: supports referential integrity (foreign key), transaction.
myisam does not support these 2.

In more details [1]:

MYISAM:

1. MYISAM supports Table-level Locking
2. MyISAM designed for need of speed
3. MyISAM does not support foreign keys hence we call MySQL with MYISAM is DBMS
4. MyISAM stores its tables, data and indexes in diskspace using separate three different files. (tablename.FRM, tablename.MYD, tablename.MYI)
5. MYISAM not supports transaction. You cannot commit and rollback with MYISAM. Once you issue a command it’s done.
6. MYISAM supports fulltext search
7. You can use MyISAM, if the table is more static with lots of select and less update and delete.

INNODB:

1. InnoDB supports Row-level Locking
2. InnoDB designed for maximum performance when processing high volume of data
3. InnoDB support foreign keys hence we call MySQL with InnoDB is RDBMS
4. InnoDB stores its tables and indexes in a tablespace
5. InnoDB supports transaction. You can commit and rollback with InnoDB

[1] What's the difference between MyISAM and InnoDB?

jQuery 1.8 update on ajax call

jQuery ajax call uses different syntax since version 1.8 [1].


Deprecation Notice: The jqXHR.success(), jqXHR.error(), and jqXHR.complete() callbacks are deprecated as of jQuery 1.8 (but still works in 1.9.1). To prepare your code for their eventual removal, use jqXHR.done(), jqXHR.fail(), and jqXHR.always() instead.

Get html in jQuery before 1.8:

$.ajax({
    url: 'test.html',
    dataType: 'html',
    success: function (data, textStatus, xhr)
    {
        console.log(data);
    },
    error: function (xhr, textStatus, errorThrown)
    {
        console.log('error: '+textStatus);
    }
});

The code above still works in 1.8. But the code below no longer works in 1.8:

$.post("get_news.php", { id: id }, function(data, status) {
    if (status == "success") {
        if ( data != '' ) {
            o.innerHTML = data;
        }
        return 1;
    } else {
        return 1; // ok
    }
}, 5);

Get html in jQuery since 1.8:

// cache: false is used to fetch the latest version
$.ajax({
    type: 'POST',
    url: "test.html",
    data: { id: id },
    dataType: 'html',
    cache: false
})
.done(function(data, textStatus, jqXHR)
{
    console.log(data);
})
.fail(function(jqXHR, textStatus, errorThrown)
{
    console.log('error: '+textStatus);
});


[1] http://www.sitepoint.com/ajax-jquery-1-8/