In simple terms, to scale horizontally is adding more servers. Vertically to increase the resources of the server.

You can find more info on [Wikipedia][1].

  [1]: https://en.wikipedia.org/wiki/Scalability#Horizontal_and_vertical_scaling

Vertical Scaling
----------------

Vertical scaling, or improving the capabilities of a node/server, gives greater capacity to the node but does not decrease the overall load on existing members of the cluster. That is, the ability for the improved node to handle existing load is increased, but the load itself is unchanged. Reasons to scale vertically include increasing IOPS, increasing CPU/RAM capacity, and increasing disk capacity.

Horizontal Scaling
------------------

Horizontal scaling, or increasing the number of nodes in the cluster, reduces the responsibilities of each member node by spreading the keyspace wider and providing additional endpoints for client connections. That is, the capacity of each individual node does not change, but its load is decreased. Reasons to scale horizontally include increasing I/O concurrency, reducing the load on existing nodes, and increasing disk capacity.

Well I have a strange problem while convert from unix timestamp to human representation using javascript

Here is timestamp

    1301090400

This is my javascript

    var date = new Date(timestamp * 1000);
    var year    = date.getFullYear();
    var month   = date.getMonth();
    var day     = date.getDay();
    var hour    = date.getHours();
    var minute  = date.getMinutes();
    var seconds = date.getSeconds();  

I expected results to be 2011 2, 25 22 00 00. But it is 2011, 2, 6, 0, 0, 0
What I miss ?

Timestamp to human readable format

I have looked everywhere. We are using a Motorola Zoom to try our tablet site testing.
The issue is that the Android Useragent is a general Useragent and there is no difference between tablet Android and mobile Android.  I don&#39;t want to just target a specific device like the Xoom Useragent since Android will most likely be on multiple tablet devices in the near future.

We are using Umbraco CMS, and we have looked at using the 51Degrees.mobi solution, and at this moment this will not work for our needs.  Maybe in the future. I know 51Degrees and some of the people at Umbraco are going to be doing some integration into Umbraco, but the final project will probably not be out for a couple of months.  
Hence, why we would like to detect the Useragent String of an Android tablet and have it not direct to our mobile site like it currently is.

If anyone knows how to detect and Android Tablet in general, not the specific device would be very helpful.



How do detect Android Tablets in general. Useragent?

In a three layer architecture with the database on the fourth, what does `scaling horizontally` and `scaling vertically` mean?

What does scale horizontally and scale vertically mean?

<p>In a three layer architecture with the database on the fourth, what does <code>scaling horizontally</code> and <code>scaling vertically</code> mean?</p>


 - What is it a BLOB?
 - How can I use it?
 - What are the differences between DBMS&#39;s BLOBs. I would like to save data using BLOBs into any DBMS and then read that BLOB with a library.



What is it exactly a BLOB in a DBMS context

I am looking for sample code in which cursor adapter is used with sqlite?

Cursor adapter and sqlite example

I need to know how to make a SQL query run daily using a SQL Server Agent job, with minimum required configuration settings.


How can I schedule a job to run a SQL query daily?

Working with databases, how can I find MAX using relational algebra?

How can I find MAX with relational algebra?

Suppose I have a model like this:

    class Book(models.Model):
        num_pages = ...
        author = ...
        date = ...

Can I create a dictionary, and then insert or update the model using it?

    d = {&quot;num_pages&quot;:40, author:&quot;Jack&quot;, date:&quot;3324&quot;}



How do I use a dictionary to update fields in Django models?

The Java tutorials say that creating a Thread is expensive. But why exactly is it expensive? What exactly is happening when a Java Thread is created that makes its creation expensive? I&#39;m taking the statement as true, but I&#39;m just interested in mechanics of Thread creation in JVM. 

&gt; Thread lifecycle overhead. Thread creation and teardown are not free. The actual overhead varies across platforms, but thread creation takes time, introducing latency into request processing, and requires some processing activity by the JVM and OS. If requests are frequent and lightweight, as in most server applications, creating a new thread for each request can consume significant computing resources.

From *Java Concurrency in Practice*  
By Brian Goetz, Tim Peierls, Joshua Bloch, Joseph Bowbeer, David Holmes, Doug Lea  
Print ISBN-10: 0-321-34960-1

Why is creating a Thread said to be expensive?

I&#39;m writing a Chrome extension that involves doing a **lot** of the following job: sanitizing strings that *might* contain HTML tags, by converting `&lt;`, `&gt;` and `&amp;` to `&amp;lt;`, `&amp;gt;` and `&amp;amp;`, respectively.

(In other words, the same as PHP&#39;s `htmlspecialchars(str, ENT_NOQUOTES)` – I don&#39;t think there&#39;s any real need to convert double-quote characters.)

This is the fastest function I have found so far:

    function safe_tags(str) {
        return str.replace(/&amp;/g,&#39;&amp;amp;&#39;).replace(/&lt;/g,&#39;&amp;lt;&#39;).replace(/&gt;/g,&#39;&amp;gt;&#39;) ;
    }

But there&#39;s still a big lag when I have to run a few thousand strings through it in one go. 

Can anyone improve on this? It&#39;s mostly for strings between 10 and 150 characters, if that makes a difference. 

(One idea I had was not to bother encoding the greater-than sign – would there be any real danger with that?)

Fastest method to escape HTML tags as HTML entities?

Serving javascript libraries from a CDN instead of your own server comes with tremendous advantages.  Less work for your server, possibility for the CDN to have a copy closer to the user than your server, but most importantly a good chance that your user&#39;s browser already has it cached from that URL.  The last one means less total work for everybody, so it&#39;s clearly a win all around, and is more likely the more often we (developers) rely on the CDNs to serve our javascript.

But the popular javascript CDNs (Google, Microsoft, others?) only host a small number of files.  For others we have the choice of hosting them ourselves, or ... using the source control server as a kind of CDN.  It&#39;s unlikely Github or similar has a geographically distributed cache of files optimized for serving globally.  But if it&#39;s common practice, then there is a decent chance that the user&#39;s browser will have it cached.  The argument of off-loading work from our servers to github is only valid if Github has willingly volunteered to do this.

So, is it common practice?  Should we encourage each other to do this?  Does Github mind?  Do they have an official policy stated?


Should Github be used as a CDN for javascript libraries?

I am using the following LINQ query for my profile page:

    var userData = from u in db.Users
                            .Include(&quot;UserSkills.Skill&quot;)
                            .Include(&quot;UserIdeas.IdeaThings&quot;)
                            .Include(&quot;UserInterests.Interest&quot;)
                            .Include(&quot;UserMessengers.Messenger&quot;)
                            .Include(&quot;UserFriends.User.UserSkills.Skill&quot;)
                            .Include(&quot;UserFriends1.User1.UserSkills.Skill&quot;)
                            .Include(&quot;UserFriends.User.UserIdeas&quot;)
                            .Include(&quot;UserFriends1.User1.UserIdeas&quot;)
                                   where u.UserId == userId
                                   select u;

It has a long object graph and uses many Includes. It is running perfect right now, but when the site has many users, will it impact performance much?

Should I do it in some other way?

How many Include I can use on ObjectSet in EntityFramework to retain performance?

I&#39;ve recently upgraded to VS 2010 and am playing around with LINQ to Dataset. I have a strong typed dataset for Authorization that is in HttpCache of an ASP.NET WebApplication.

So i wanted to know what actually is the fastest way to check if a user is authorized to do something. [Here][1] is my datamodel and some other informations if somebody is interested.

I have checked 3 ways:

 1. direct **database**
 2. LINQ query with **Where** conditions as &quot;Join&quot; - Syntax
 3. LINQ query with **Join** - Syntax

These are the results with 1000 calls on each function:

**1.Iteration:**

 1. 4,2841519 sec.
 2. 115,7796925 sec.
 3. 2,024749 sec.

**2.Iteration:**

 1. 3,1954857 sec.
 2. 84,97047 sec.
 3. 1,5783397 sec.

**3.Iteration:**

 1. 2,7922143 sec.
 2. 97,8713267 sec.
 3. 1,8432163 sec.

**Average:**

 1. Database: 3,4239506333 sec.
 2. Where: 99,5404964 sec.
 3. Join: 1,815435 sec.

Why is the Join-version so much faster than the where-syntax which makes it useless although as a LINQ newbie it seems to be the most legible. Or have i missed something in my queries?

Here are the LINQ queries, i skip the database:

**Where**:   

    Public Function hasAccessDS_Where(ByVal accessRule As String) As Boolean
        Dim userID As Guid = DirectCast(Membership.GetUser.ProviderUserKey, Guid)
        Dim query = From accRule In Authorization.dsAuth.aspnet_AccessRule, _
                    roleAccRule In Authorization.dsAuth.aspnet_RoleAccessRule, _
                    role In Authorization.dsAuth.aspnet_Roles, _
                    userRole In Authorization.dsAuth.aspnet_UsersInRoles _
                    Where accRule.idAccessRule = roleAccRule.fiAccessRule _
                    And roleAccRule.fiRole = role.RoleId _
                    And userRole.RoleId = role.RoleId _
                    And userRole.UserId = userID And accRule.RuleName.Contains(accessRule)
                    Select accRule.idAccessRule
        Return query.Any
    End Function

**Join:**

    Public Function hasAccessDS_Join(ByVal accessRule As String) As Boolean
        Dim userID As Guid = DirectCast(Membership.GetUser.ProviderUserKey, Guid)
        Dim query = From accRule In Authorization.dsAuth.aspnet_AccessRule _
                    Join roleAccRule In Authorization.dsAuth.aspnet_RoleAccessRule _
                    On accRule.idAccessRule Equals roleAccRule.fiAccessRule _
                    Join role In Authorization.dsAuth.aspnet_Roles _
                    On role.RoleId Equals roleAccRule.fiRole _
                    Join userRole In Authorization.dsAuth.aspnet_UsersInRoles _
                    On userRole.RoleId Equals role.RoleId _
                    Where userRole.UserId = userID And accRule.RuleName.Contains(accessRule)
                    Select accRule.idAccessRule
        Return query.Any
    End Function

Thank you in advance.


----------


**Edit**: after some improvements on both queries to get more meaningful perfomance-values, the advantage of the JOIN is even many times greater than before:

**Join**:

    Public Overloads Shared Function hasAccessDS_Join(ByVal userID As Guid, ByVal idAccessRule As Int32) As Boolean
        Dim query = From accRule In Authorization.dsAuth.aspnet_AccessRule _
                       Join roleAccRule In Authorization.dsAuth.aspnet_RoleAccessRule _
                       On accRule.idAccessRule Equals roleAccRule.fiAccessRule _
                       Join role In Authorization.dsAuth.aspnet_Roles _
                       On role.RoleId Equals roleAccRule.fiRole _
                       Join userRole In Authorization.dsAuth.aspnet_UsersInRoles _
                       On userRole.RoleId Equals role.RoleId _
                       Where accRule.idAccessRule = idAccessRule And userRole.UserId = userID
                 Select role.RoleId
        Return query.Any
    End Function

   
**Where**:

    Public Overloads Shared Function hasAccessDS_Where(ByVal userID As Guid, ByVal idAccessRule As Int32) As Boolean
        Dim query = From accRule In Authorization.dsAuth.aspnet_AccessRule, _
               roleAccRule In Authorization.dsAuth.aspnet_RoleAccessRule, _
               role In Authorization.dsAuth.aspnet_Roles, _
               userRole In Authorization.dsAuth.aspnet_UsersInRoles _
               Where accRule.idAccessRule = roleAccRule.fiAccessRule _
               And roleAccRule.fiRole = role.RoleId _
               And userRole.RoleId = role.RoleId _
               And accRule.idAccessRule = idAccessRule And userRole.UserId = userID
               Select role.RoleId
        Return query.Any
    End Function

Result for 1000 calls (on a faster computer)
----------
1. Join | 2. Where

**1.Iteration:**

 1. 0,0713669 sec.
 2. 12,7395299 sec.

**2.Iteration:**

 1. 0,0492458 sec.
 2. 12,3885925 sec.

**3.Iteration:**

 1. 0,0501982 sec.
 2. 13,3474216 sec.

**Average:**

 1. Join:  0,0569367 sec.
 2. Where: 12,8251813 sec.

-------------------------
Join is 225 times faster 

**Conclusion:** avoid WHERE to specify relations and use JOIN whenever possible(definitely in [LINQ to DataSet][2] and `Linq-To-Objects` in general).


  [1]: https://stackoverflow.com/questions/5518746/how-to-join-with-linq-to-typed-dataset-composite-key-issue
  [2]: http://msdn.microsoft.com/en-us/library/bb386977.aspx

Why is LINQ JOIN so much faster than linking with WHERE?

I&#39;m building a chat app and I want a full history off all messages ever sent in the chat conversation. At the moment I am storing each message as a single row in a table called &#39;messages&#39;. I am aware that this table could grow huge as even small messages like &#39;Hi&#39; would have their own database record.

Can anyone recommend a more scalable mysql solution? I don&#39;t require the individual messages to be searchable, editable or deletable. Could the whole conversation be stored in one huge field?

Would love to hear your ideas!

Best way to store chat messages in a database?

[High Scalability][1] mentions feature flags here:

*[5 things toxic to scalability][2]*, *&quot;5. Lack of Feature Flags&quot;*

What exactly are feature flags?

  [1]: http://highscalability.com/
  [2]: http://www.iheavy.com/2011/08/26/5-things-are-toxic-to-scalability/



What is a &quot;feature flag&quot;?

I have read the following text in a [technical blog][1] discussing the advantages and disadvantages of NoSQL:

&gt; &quot;For years, in order to improve performance on database servers, database administrators have had to buy bigger servers as the database
&gt; load increases (scaling up) instead of distributing the database
&gt; across multiple “hosts” as the load increases (scaling out). RDBMS do
&gt; not typically scale out easily, but the newer NoSQL databases are
&gt; actually designed to expand easily to take advantage of new nodes and
&gt; are usually designed with low-cost commodity hardware in mind.&quot;

I became confused about the scalability of RDBMS and NoSQL.

My confusion are:

 1. Why RDBMS are less able to scale out? And the reason of buying bigger servers instead of buying more cheap ones.
 2. Why NoSQL is more able to scale out?

  [1]: http://tekedia.com/12083/nosql-database-advantages-and-disadvantages/

Why NoSQL is better at &quot;scaling out&quot; than RDBMS?

I read many articles comparing programming languages. 

There is a word that comes often: _scalability_. I actually tried to look for a simple and clear explanation, but haven&#39;t found anything.

Can you explain what the _scalability_ term means?


What does &quot;scalability&quot; mean?

I&#39;ve heard many people using both terms interchangeably. However, in my opinion there is difference between them:

**SCALABILITY** - ability of a *software system* to process higher amount of workload on its current hardware resources (*scale up*) or on current and additional hardware resources (*scale out*) without application service interruption;

**ELASTICITY** - ability of the *hardware layer* below (usually cloud infrastructure) to increase or shrink the amount of the physical resources offered by that hardware layer to the software layer above. The increase / decrease is triggered by business rules defined in advance (usually related to application&#39;s demands). The increase / decrease happens on the fly without physical service interruption. 

Again, scalability is a characteristic of a software architecture related to serving higher amount if workload, where elasticity is a characteristic of the physical layer below, entirely related to hardware budget optimizations. 

Have I got the difference between these two non-functional architectural characteristics right?
May someone give specific examples, so we could draw more distinctive border between these two terms?


Content Type	Original Author	Original Content on Stackoverflow
Question	satish	View Question on Stackoverflow
Solution 1 - Database	edmz	View Answer on Stackoverflow
Solution 2 - Database	BigSack	View Answer on Stackoverflow

What does scale horizontally and scale vertically mean?

Database Problem Overview

Database Solutions

Solution 1 - Database

Solution 2 - Database

Vertical Scaling

Horizontal Scaling

How do detect Android Tablets in general. Useragent?

Timestamp to human readable format

Attributions