[Dbix-class] DBIx::Class::Ordered changes.

[Peter Rabbitson]

On Thu, Sep 20, 2012 at 11:50:58AM +0100, Will Crawford wrote:
> On 20 September 2012 11:19, Peter Rabbitson <rabbit+dbic at rabbit.us> wrote:
> 
> > I experimented with some stuff that is still on my disk, trying to set the
> > nextpos to (SELECT pos .... ) + 1. It worked for most engines except for Pg
> > for which this is not an atomic operation. Then I laughed at Pg and forgot
> > about the whole thing. I need to get back to it at some point.

This is a describing a different problem froma thread a year ago. It is what 
happens when new rows are inserted *concurrently* with pos unspecified (i.e. 
pushed to the end of the stack)

> Ipricing=# create table test1 ( id serial primary key, value text );
> NOTICE:  CREATE TABLE will create implicit sequence "test1_id_seq" for
> serial column "test1.id"
> NOTICE:  CREATE TABLE / PRIMARY KEY will create implicit index
> "test1_pkey" for table "test1"
> CREATE TABLE
> pricing=# create table test2 ( id serial primary key, test1_id integer
> not null references test1, position integer not null, unique
> (test1_id, position) );
> NOTICE:  CREATE TABLE will create implicit sequence "test2_id_seq" for
> serial column "test2.id"
> NOTICE:  CREATE TABLE / PRIMARY KEY will create implicit index
> "test2_pkey" for table "test2"
> NOTICE:  CREATE TABLE / UNIQUE will create implicit index
> "test2_test1_id_position_key" for table "test2"
> CREATE TABLE
> pricing=# insert into test1 (value) values ('first');
> INSERT 0 1
> pricing=# insert into test2 (test1_id, position) values (1, 0);
> INSERT 0 1
> pricing=# insert into test2 (test1_id, position) values (1, 1);
> INSERT 0 1
> pricing=# insert into test2 (test1_id, position) values (1, 2);
> INSERT 0 1
> pricing=# insert into test2 (test1_id, position) values (1, 3);
> INSERT 0 1
> pricing=# insert into test2 (test1_id, position) values (1, 5);
> INSERT 0 1
> pricing=# insert into test2 (test1_id, position) values (1, 4);
> INSERT 0 1
> pricing=# delete from test2 where test1_id = 1 and position = 2 ;
> DELETE 1
> pricing=# update test2 set position = position - 1 where test1_id = 1
> and position between 3 and 5 ;
> UPDATE 3

The reason Bill started this thread is that the above apparently did not 
work for him. I am now confused...