vLeJyVKB

1create table File
2	(
3		 id char(30) not null,
4		 position int not null unique,
5		 primary key (id)
6		);
7
8create table Cluster
9	(
10		id int not null auto_increment,
11		next int not null unique,
12		primary key (id)
13		);
14
15create procedure Copy
16	@fileId char(30)
17	as
18	begin
19		set transaction isolation level read uncommitted
20		begin transaction
21			declare @curr int
22			declare @prev int
23			set @curr = (select position from File where id = @fileId)
24			set @prev = null
25
26			while @curr <> -1
27			begin
28				set @lastId = 0
29				while exists (select * from Cluster where id = @lastId)
30				begin
31					@lastId = @lastId + 1;
32				end			
33
34				insert into Cluster
35				values (@lastId, -1) 
36				if @prev <> null 
37				begin
38					update Cluster
39					set next = @lastId
40					where id = @prev
41				end
42				set @prev = @listId
43				set @curr = (select next from Clister where id = @curr)
44			end