Q: Full text search
PostgreSQL
Elasticsearch
Sphinx - fully developed
Solr - fully developed
How does rails index works ?
Facts:
map outputs an array with the ability to do some computational on it.
Facts:
user = User.where(:name => 'tapan') --> It builds sql query
user.first --> Execute the query in other words it now talks with databases.
NameError
NoMethodError
Curiosity: Just know commented on this video, waiting for approval
http://www.youtube.com/watch?v=mBXGBbEbXZY
Q. Why do we use symbol ?
bihar = {state: 'bihar', capital: 'patna'}
then, india.keys.map(&:object_id) => [163848, 3119208] (some arbitrary ids)
karnataka = {state: 'karnataka', capital: 'bangalore'}
india.keys.map(&:object_id) => [163848, 3119208] (some arbitrary ids)
Here it returns the same object id for keys(state, capital).
So it references the same symbol and thus saves memory.
Q. Why does Symbol.all_symbols.include? :hello
always return true
=> It happens as because it will go and first check in the array whether this particular symbols exists ? and it happens to be present there then returns true : else it will be pushed to the array and then return true
Concatenation
1. puts "tapan" + "sharma"
2. puts "tapan".concat("sharma")
3. puts "tapan" "sharma"
Chaining if's
puts "hello boy" if 1 == 1 if 2 == 2
Ruby zip method
order = %w{1 2 3 4}
animals = %w{ant bat cat dog elephant}
p order.zip(animals)
=> [["1", "ant"], ["2", "bat"], ["3", "cat"], ["4", "dog"]]
p Hash[order.zip(animals)]
=> {"1"=>"ant", "2"=>"bat", "3"=>"cat", "4"=>"dog"}
Array creation
a = [*1..8]
Json
require 'json'
h = {a: 'apple', b: 'boy', c: 'cat'}
j h
=> {"a":"apple","b":"boy","c":"cat"}
jj h
=> {
"a": "apple",
"b": "boy",
"c": "cat"
}
__method__ :
check for method name.
source_location :
this locates the method.
Difference between scopes and class method
http://blog.plataformatec.com.br/2013/02/active-record-scopes-vs-class-methods/
Method Look up in Ruby.
Very well explained and written.
http://blog.jcoglan.com/2013/05/08/how-ruby-method-dispatch-works/comment-page-1/#comment-11917"
StringInquirer is a subclass of String
Command to create dump and restore
pg_dump dbname > outfile
psql dbname < infile
Take dump of some tables in postgresql
pg_dump --table=tutor_invoices --table=students veritas_development > out.sql
