Rails - Jul 2010 - newb here trying to understand an issue with rolling back migrations then re-running them

I''m sure this is total newb (since I am pretty newb) but I''m
curious what
the issue is here. I attempt to role back all my migrations which I''m
doing
with

rake db:migrate VERSION=0
(in /Users/rick/projects/rails/sillymeters)
==  CreateSessions: never migrated, skipping
=================================
==  CreateUsers: reverting
===================================================-- drop_table(:users)
   -> 0.0011s
==  CreateUsers: reverted (0.0012s)
==========================================
==  CreateMeters: reverting
==================================================-- drop_table(:meters)
   -> 0.0008s
==  CreateMeters: reverted (0.0009s)
=========================================
etc..

Note the first one says "CreateSessions: never migrated, skipping"

When I then go to run the migrations, most go through fine, but then  I get
the following error when it tries to run the CreateSessions migration:

 ~/projects/rails/sillymeters(master) $ rake db:migrate
(in /Users/rick/projects/rails/sillymeters)
==  CreateSessions: migrating
================================================-- create_table(:sessions)-
rake aborted!
An error has occurred, this and all later migrations canceled:

SQLite3::SQLException: table "sessions" already exists: CREATE TABLE
"sessions" ("id" INTEGER PRIMARY KEY AUTOINCREMENT NOT NULL,
"session_id"
varchar(255) NOT NULL, "data" text, "created_at" datetime,
"updated_at"
datetime)


I''m assuming that each application has its own instance of SQLLite so
I''m
curious how this error is occurring or what I need to do to fix it. I
''think'' I might be getting this because it''s possible
I did at one point
have a similar migration that created the Session table, but then I deleted
that migration and created it as a new one with a new name. The table name
was the same though "sessions" so I don''t get what is going
on.

The migration in question looks like:

class CreateSessions < ActiveRecord::Migration
  def self.up
    create_table :sessions do |t|
      t.string :session_id, :null => false
      t.text :data
      t.timestamps
    end

    add_index :sessions, :session_id
    add_index :sessions, :updated_at
  end

  def self.down
    drop_table :sessions
  end
end

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>
> Note the first one says "CreateSessions: never migrated,
skipping"
>
> When I then go to run the migrations, most go through fine, but then  I get
> the following error when it tries to run the CreateSessions migration:
>
>  ~/projects/rails/sillymeters(master) $ rake db:migrate
> (in /Users/rick/projects/rails/sillymeters)
> ==  CreateSessions: migrating
> ================================================> --
create_table(:sessions)-
> rake aborted!
> An error has occurred, this and all later migrations canceled:
>
> SQLite3::SQLException: table "sessions" already exists: CREATE
TABLE
> "sessions" ("id" INTEGER PRIMARY KEY AUTOINCREMENT NOT
NULL, "session_id"
> varchar(255) NOT NULL, "data" text, "created_at"
datetime, "updated_at"
> datetime)
>
> I''m assuming that each application has its own instance of SQLLite
so I''m
> curious how this error is occurring or what I need to do to fix it. I
> ''think'' I might be getting this because it''s
possible I did at one point
> have a similar migration that created the Session table, but then I deleted
> that migration and created it as a new one with a new name. The table name
> was the same though "sessions" so I don''t get what is
going on.
>
Rails tracks migrations that have be run with the schema_migrations
(which contains the numerical identifier for each migration). If you
created a new migration then that migration won''t be recorded as
having being run (which is why migrate VERSION=0 doesn''t do anything)
but the table is of course still there, so trying to create it again
raises an error

Fred
> The migration in question looks like:
>
> class CreateSessions < ActiveRecord::Migration
>   def self.up
>     create_table :sessions do |t|
>       t.string :session_id, :null => false
>       t.text :data
>       t.timestamps
>     end
>
>     add_index :sessions, :session_id
>     add_index :sessions, :updated_at
>   end
>
>   def self.down
>     drop_table :sessions
>   end
> end
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You can run the following command: 
script/dbconsole

And then manually drop the sessions table (drop sessions). Then try full
rollbacks and migrations again.

Sent from my iPhone

On Jul 30, 2010, at 2:36 AM, Rick R
<rickcr-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org> wrote:
> I''m sure this is total newb (since I am pretty newb) but
I''m curious what the issue is here. I attempt to role back all my
migrations which I''m doing with
> 
> rake db:migrate VERSION=0
> (in /Users/rick/projects/rails/sillymeters)
> ==  CreateSessions: never migrated, skipping
=================================>
> ==  CreateUsers: reverting
===================================================> -- drop_table(:users)
>    -> 0.0011s
> ==  CreateUsers: reverted (0.0012s)
==========================================>
> ==  CreateMeters: reverting
==================================================> -- drop_table(:meters)
>    -> 0.0008s
> ==  CreateMeters: reverted (0.0009s)
=========================================>
> etc..
> 
> Note the first one says "CreateSessions: never migrated,
skipping"
> 
> When I then go to run the migrations, most go through fine, but then  I get
the following error when it tries to run the CreateSessions migration:
> 
>  ~/projects/rails/sillymeters(master) $ rake db:migrate
> (in /Users/rick/projects/rails/sillymeters)
> ==  CreateSessions: migrating
================================================> -- create_table(:sessions)-
> rake aborted!
> An error has occurred, this and all later migrations canceled:
> 
> SQLite3::SQLException: table "sessions" already exists: CREATE
TABLE "sessions" ("id" INTEGER PRIMARY KEY AUTOINCREMENT NOT
NULL, "session_id" varchar(255) NOT NULL, "data" text,
"created_at" datetime, "updated_at" datetime)
> 
> 
> I''m assuming that each application has its own instance of SQLLite
so I''m curious how this error is occurring or what I need to do to fix
it. I ''think'' I might be getting this because it''s
possible I did at one point have a similar migration that created the Session
table, but then I deleted that migration and created it as a new one with a new
name. The table name was the same though "sessions" so I
don''t get what is going on.
> 
> The migration in question looks like:
> 
> class CreateSessions < ActiveRecord::Migration
>   def self.up
>     create_table :sessions do |t|
>       t.string :session_id, :null => false
>       t.text :data
>       t.timestamps
>     end
> 
>     add_index :sessions, :session_id
>     add_index :sessions, :updated_at
>   end
> 
>   def self.down
>     drop_table :sessions
>   end
> end
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Check to see if you have duplicate code in any of your migrations to
create this table:
> SQLite3::SQLException: table "sessions" already exists: CREATE
TABLE
> "sessions" ("id" INTEGER PRIMARY KEY AUTOINCREMENT NOT
NULL, "session_id"
> varchar(255) NOT NULL, "data" text, "created_at"
datetime, "updated_at"
> datetime)
This can easily happen if you have code to create all your tables in
the main CreateDatabase migration file, then run script/generate to
generate scaffolding or a model for an existing table.  The generator
script will create a new migration with table creation code, causing
rake to choke the next time you do a migration.

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