ruby - Rescue block did not run in rails migration script -

i have generated following migration:

class addmarketstatusidtoproducts < activerecord::migration   def change     add_column :products, :market_status_id, :integer   end end 

but started raising following error @ heroku:

20150816131733 addmarketstatusidtoproducts: migrating ===================== -- add_column(:products, :market_status_id, :integer)    (1.7ms)  alter table "products" add "market_status_id" integer pg::undefinedtable: error:  relation "products" not exist : alter table "products" add "market_status_id" integer    (1.0ms)  rollback rake aborted! standarderror: error has occurred, , later migrations canceled: 

error message quite clear, used following migration script instead:

class addmarketstatusidtoproducts < activerecord::migration   def change     begin       add_column :products, :market_status_id, :integer     rescue pg::undefinedtable       create_table :products |t|         t.float :price          t.timestamps null: false       end     end   end end 

but still getting same error message!! don't understand, why rescue code did not run?

i don't know why rescue block not running think error 1 standarderror: error has occurred, , later migrations canceled: standarderror can handle may be: rescue standarderror => error. guess don't know this.

but correct way above is:

class addmarketstatusidtoproducts < activerecord::migration   def change     if table_exists?("products")       add_column :products, :market_status_id, :integer     else       create_table :products |t|         t.float :price         t.integer :market_status_id         t.timestamps null: false       end     end   end end 

rails has provided methods table_exists? , column_exists? this. have never used know can done. please check syntax once not 100% sure syntax.

hope helps.