How active record is automatically setting up the autoincremental value of ID?

Posted by piemesons on Stack Overflow See other posts from Stack Overflow or by piemesons
Published on 2010-04-21T07:28:01Z Indexed on 2010/04/21 7:33 UTC
Read the original article Hit count: 300

Filed under:

activerecord

|

database

|

rails

|

doctrine

Here this is what we are doing:--

an_order = Order.new 
an_order.name   = "Dave Thomas" 
an_order.email  = "[email protected]" 
an_order.address = "123 Main St" 
an_order.pay_type = "check" 
an_order.save

Now it will insert a new row in orders table right. I m having a ID column in that table. Now suppose after inserting this record the value of the ID corresponding to this record is 100. Now how this 100 value came to know?

Does the previous value of ID ie 99 (Suppose) is stored somewhere in some variable/file in the ORM layer

or

before inserting this value a query was fired to know about the last inserted value or

database is itself doing that or

anything else???

© Stack Overflow or respective owner

Related posts about activerecord

Rails & ActiveRecord: Appending methods to models that inherit from ActiveRecord::Base

as seen on Stack Overflow - Search for 'Stack Overflow'
I have a standard ActiveRecord model with the following: class MyModel < ActiveRecord::Base custom_method :first_field, :second_field end At the moment, that custom_method is picked up by a module sent to ActiveRecord::Base. The functionality basically works, but of course, it attaches itself… >>> More
Rails ActiveRecord - Best way to perform an include?

as seen on Stack Overflow - Search for 'Stack Overflow'
I have three models: class Book < ActiveRecord::Base has_many :collections has_many :users, :through => :collections end class User < ActiveRecord::Base has_many :collections has_many :books, :through => :collections end class Collection < ActiveRecord::Base belongs_to… >>> More
Getting types of the attributes in an ActiveRecord object

as seen on Stack Overflow - Search for 'Stack Overflow'
I would like to know if it is possible to get the types (as known by AR - eg in the migration script and database) programmatically (I know the data exists in there somewhere). For example, I can deal with all the attribute names: ar.attribute_names.each { |name| puts name } .attributes just… >>> More
Changing ActiveRecord attribute value in before_save hook

as seen on Stack Overflow - Search for 'Stack Overflow'
I needed to fix the encoding of an ActiveRecord attribute and decided to do it in a before_save hook. And at this point I noticed an unexpected feature. When I wanted to change the value of the attribute, simple using the attribute_name=XY did not work as I expected. Instead of that I needed to use… >>> More
Conditions with whitespaces in activerecord find

as seen on Stack Overflow - Search for 'Stack Overflow'
So i am trying to do this Order.find :all, :conditions => "org = 'test org'" what ends up firing is SELECT * FROM `orders` WHERE (org = 'test org') the whitespace in the argument gets stripped. what am i missing.. im really stumped here. please help! >>> More

Related posts about database

SQL SERVER Retrieve and Explore Database Backup without Restoring Database Idera virtual database

as seen on Dot net Slackers - Search for 'Dot net Slackers'
I recently downloaded Ideras SQL virtual database, and tested it. There are a few things about this tool which caught my attention.My ScenarioIt is quite common in real life that sometimes observing or retrieving older data is necessary; however, it had changed as time passed by. The full database… >>> More
Cloning A Database On The Same Server Using Rman Duplicate From Active Database

as seen on Oracle Blogs - Search for 'Oracle Blogs'
To clone a database using Rman we used to require an existing Rman backup, on 11g we can clone databases using the "from active" database option. In this case we do not require an existing backup, the active datafiles will be used as the source for the clone. In order to clone with the source database… >>> More
cPickle ImportError: No module named multiarray

as seen on Stack Overflow - Search for 'Stack Overflow'
Hello, I'm using cPickle to save my Database into file. The code looks like that: def Save_DataBase(): import cPickle from scipy import * from numpy import * a=Results.VersionName #filename='D:/results/'+a[a.find('/')+1:-a.find('/')-2]+Results.AssType[:3]+str(random.randint(0,100))+Results.Distribution+"… >>> More
SQL SERVER – 2008 – Introduction to Snapshot Database – Restore From Snapshot

as seen on SQL Authority - Search for 'SQL Authority'
Snapshot database is one of the most interesting concepts that I have used at some places recently. Here is a quick definition of the subject from Book On Line: A Database Snapshot is a read-only, static view of a database (the source database). Multiple snapshots can exist on a source database and… >>> More
OTN ???? ?????? ???????

as seen on Oracle Blogs - Search for 'Oracle Blogs'
Database ?? Database ??????? Database ?????????? Java WebLogic Server/????????·???? SOA/BPM/????? ???????/???? ID??/?????? ?????EPM/BI EPM/BI ??????? EPM/BI ???? OS/??? ???? ????? MySQL Database ?? ???? ?? ????????? ??? ?? ORACLE MASTER… >>> More