Developers POV !

[sonuoommen]

Its No "No Structured Query Language"

Alice: Hey! Are you on the new Project in which they are going to use a different database ? Bob: Yes, they are gonna use NoSQL for that project. Alice: What is it... No Structured Query Language..eh?. Bob: Oh no they call it "Not only SQL" actually. Alice: Great ! that explains a lot, What exactly is Nosql ?, I mean this must be some anti SQL movements, dont you think the name makes it kinda obvious. Bob: No, NoSql was initially nothing but a catchy twitter hash tag, with the purpose of attracting people for a meetup,#NoSQL, just like red black tree, which got it name because the guy who invented it had just two inks to distinguish 2 types of node "red" and "black" and Voila! the name just "happened". Alice: How different is it from the traditional table databases ? Bob: Well, to start with there are no table and most datamodels in NoSQL are not relational. They store data as a whole like a object, unlike RDBMS in which we rip of data from the object and store it in different tables. Alice: Data as a whole object, but that makes no sense. Bob: Yeah it doesn't if you think of it from a RDBMS point of view. Think of this as your assignment notebook. Your note is the database and assignments is the collection containing all your assignments. Then each assignment is an object and while storing it we store it as a whole without breaking it down. ##collection Assignments: ##object 1 Assignment 1: <all your notes, including title, date and all possible data in that assignment> #object 2 Assignment 2: <data> . . . Alice: Well dont you this would lead to a lot of data and redundancy ? Bob: Yes, but we dont have to worry about that. Todays databases are not costly as they used to be and moreover today data is more valuable than the storage cost. Alice: And what exactly does data models in NoSQl mean ? Bob: Well this is what i found "A data model is a conceptual representation of the data structures that are required by an database. The data structures include the data objects, the associations between data objects, and the rules which govern operations on the objects. As the name implies, the data model focuses on what data is required and how it should be organized." They are 4 data models in NoSQL 1. Key-Value Pair 2. Document Type 3. Column-Family type 4. Graph Alice: Can you speak in English ? Bob: Ok lets take it one at a time: Key-Value Pair- Its basically like a big hash table, wherein we have a key and corresponding to that key we have some value stored. For eg: Take our example of Assignments Here Assignment1 is a "Key" and its corresponding data is the "value". Alice: mmmm... Bob: Ok here is a better one, Lets say we want to store Ruby on Rails Pvt. Ltd. address in US and India key value "India" {"Ruby Software Resources, 3740 DaVinci Court Suite 300 Norcross GA, 30092, Phone: [phone], Fax: [phone], Email: [email protected]"} "USA" {"Pamba Building, Trivandrum Technopark, Kerala, India -695581, Phone: [phone], Email: [email protected]"} Alice: Oh okay, I got it, you dont store state and country at a different location like we do in RDBMS to prevent redundancy. So we only need to get the kay and we can have all the data without having to define any relation. I see we dont have any schema here, so NoSQL is schema less and unstructured ? Bob: Mostly, yes. But let me introduce you to the Document Type first. This is almost like Key-Value pair, the difference being that it is kinda semi-structured. for eg: if we were to store the address data in Document data type it would look like this {office : "Ruby on Rails Pvt Ltd", location : "USA", Address : "3740 DaVinci Court Suite 300 Norcross GA, 30092", Phone: "[phone]", Fax: "770-234-6195", Email: "[email protected]" } {office : "Ruby on Rails Pvt Ltd", location : "India", Address : "Pamba Building Trivandrum Technopark, Kerala, India -695581", Phone: "[phone]", Email: "[email protected] } Alice: Oh this looks like a JSON file. Bob: Exactly, Document type databases uses JSON documents to store records. So you can see now that this is kinda structured, yet no definite schema is defined. Alice: Okay, so you can get specific data out of a object which was not possible with key-value pair, like if only we want to know the phone number, we can query for that specifically. Bob: Exactly. To be contd...

[sonuoommen]

Coding conventions and styles for Ruby in a Nutshell

Coding Conventions are very important part of Software Development. Following a specific coding convention just makes life of a developer working on your code much easier.

While some conventions are necessary for readability, for example, keeping the length of a line of code well within the size of the screen so that we don’t have to scroll both horizontally and vertically after each line.

Given below are some very common and neglected scenario where we should use this convention to enhance readability and also performance in some cases. Most of us have been through Ruby/Rails style-guides, so I am only gonna present points in a very sharp and “to the point” manner,some of these practices are to be adopted and some that need to be avoided.

1. Ternary operators must not be nested. We can use if/else constructs in some of the cases like:

# bad some_condition ? (nested_condition ? nested_something : nested_something_else) : something_else

# good if some_condition nested_condition ? nested_something : nested_something_else else something_else end

2.(i) Prefer {…} over do…end for single-line blocks.

(ii) Avoiding use of {…} for multi-line blocks.

names = ["Venkat", "Sonu", "Kurian"]

# good names.each {|name|puts name }

# bad names.each do|name| puts name end

# good names.select {|name|name.start_with?(“S”) }.map {|name|name.upcase }

# bad names.select do|name| name.start_with?(“S”) end.map {|name|name.upcase }

3.(i) Use %w for defining array of words.

# bad STATES = ['one', 'two', 'three']

# good STATES = %w(one two three)

(ii) Use %i for defining array of symols.

# bad STATES = [:one, :two, :three]

# good STATES = %i(one two three)

(iii) While accessing the first or last element of an array, use array.first or array.last over array[0] or array[-1].

(iv) While dealing with unique elements, use Set instead of Array . Set implements a collection of unordered values with no duplicates.

  Set is a hybrid of Array’s intuitive inter-operation facilities and Hash’s fast lookup. 

  The difference between Array and Set is that, an array is an ordered list of key/value pair where keys(index) are always integer and the values are objects. Whereas a set is an un-ordered pool of unique objects.

4.(i) Use symbols instead of strings as hash keys.

# bad hash = { ‘one’ => 1, ‘two’ => 2, ‘three’ => 3 }

# good

hash = { one: 1, two: 2, three: 3 }

(ii) Avoid the use of mutable objects as hash keys.

Use the hash literal syntax when your hash keys are symbols.

# bad hash = {:one => 1, :two => 2, :three => 3 }

# good hash = { one: 1, two: 2, three: 3 }

(iii) Use Hash#key? instead of Hash#has_key? and Hash#value? instead of Hash#has_value?.

# bad hash.has_key?(:test) hash.has_value?(value)

# good hash.key?(:test) hash.value?(value)

(iv) Use Hash#fetch when dealing with hash keys that should be present.

heroes = { batman: ‘Bruce Wayne’, superman: ‘Clark Kent’ }

# bad – if we make a mistake we might not spot it right away heroes[:batman] # => “Bruce Wayne” heroes[:supermann] # => nil

# good – fetch raises a KeyError making the problem obvious heroes.fetch(:supermann)

(v) Introduce default values for hash keys via Hash#fetch as opposed to using custom logic.

batman = { name: ‘Bruce Wayne’, is_evil: false }

# bad – if we just use || operator with falsy value we won’t get the expected result

batman[:is_evil] || true # => true

# good – fetch work correctly with falsy values

batman.fetch(:is_evil, true) # => false

(vi) Prefer the use of the block instead of the default value in Hash#fetch.

batman = { name: ‘Bruce Wayne’ }

# bad – if we use the default value, we eager evaluate it, so it can slow the program down if done multiple times batman.fetch(:powers, get_batman_powers) # get_batman_powers is an expensive call

# good – blocks are lazy evaluated, so only triggered in case of KeyError exception batman.fetch(:powers) { get_batman_powers }

These are some very common and very useful convention that can enhance readability of your code and would help in maintaining, understanding the software design easily and quickly.

reference-https://github.com/bbatsov/ruby-style-guide,https://github.com/bbatsov/rails-style-guide

[sonuoommen]

Google IT! The Right Way

Any developer working on a new project or environment, spends an awful lot of time trying to find solution to his problem or best ways to tackle a particular problem over the Internet or in other word googling. Most of the search results we obtain are polluted with unwanted pages. As a result we end up filtering the results manually trying to find the results best suited for us. Isn’t thas the reason why we have search engines in the first place – to filter data and provide us with the most suitable result. So what’s stopping us from generating the result we are actually looking out for ?

Lets look at a very simple example, say we need to find the list of movies that are played across various theaters in Trivandrum, a normal Google query of a layman would be something like:

“movies running at trivandrum“

or say, to find the list of Presidents of India from 1970 to 2012, the query would look something like

“list of presidents of india from 1970 to 2012”

Queries like these may or may not fetch us the right result, but we are not interested in ordinary ways cause thats what ordinary people do. So lets see how we can write a better query for what we are looking for:

1970..2012 presidents india##providing range to obtain accurate results.

Movie:695001##695001 being the PIN no. of Trivandrum

The above search query appears much more elegant and is by fact more efficient in generating better search results.

A very important trick to obtain accurate search results is to eliminate undesired results, rather than filtering manually we can make Google do the job. For example say we need to query result regarding ruby language and don’t wish any page result with ruby on rails.

ruby -rails

will generate just the results with ruby and no result of ruby on rails. Some other time you maybe looking for results containing some exact term or phrase, how do we make sure that those terms are not ignored ?. Simply wrap it in quotes. So if I want to find the document containing the phrase webrick script software. My query should be something like

ruby on rails “webrick script software”

as a matter of fact the above query generated only a single search result, that is pretty accurate.

Now sometimes we want to search certain terms or phrase from a particular site, for example about CSRF fromhttp://rubyonrails.org/

csrf site:rubyonrails.org/

Sometimes we may know a phrase but our recollection of that might not be vivid, say we know its something related to ‘active record’ and ends with ‘interface’:

active record:*interface

will search for anything results with anything in between active record and interface and voila! our result will be Active Record Query Interface.

Some of the most important and most ignored facts about googling are:

Advanced search feature of Google, which can be accessed by clicking on Settings > Advanced Search.

Some common words, called “stop words” (such as the, on, where, how, de, la, as well as certain single digits and single letters) generally don’t add meaning to a search.

Stop words appear on so many pages that searching for them usually doesn’t help you find relevant results.

We can use Search tools option to specify the time, country etc.

Don’t worry about punctuation, as they are mostly ignored. This includes @#%^()+{}\ and other special characters.

Ignore spelling, Google spell checker automatically defaults to the most common spelling of a given word.

Don’t worry about case, search isn’t case sensitive.

And most importantly lesser the number of keywords, broader the result you yield.

So lets Google towards better results.