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: 378

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???

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