eGTa01zi

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,
11		next int not null unique,
12		primary key (id)
13		);
14
15
16create procedure Copy
17	@fileId char(30)
18	as
19	begin		
20		declare @curr int
21		declare @prev int
22		declare @first int
23		set @curr = (select position from File where id = @fileId)
24		set @prev = null
25		set @first = null
26
27		while @curr <> -1
28		begin
29			while 1 = 1
30			begin
31				set transaction isolation level read uncommitted
32				begin transaction
33					begin try
34						@declare lastId int
35						set @lastId = 0
36						while exists (select * from Cluster where id = @lastId)
37						begin
38							set @lastId = @lastId + 1;
39						end			
40
41						insert into Cluster
42						values (@lastId, -1) 
43						if @prev <> null 
44						begin
45							update Cluster
46							set next = @lastId
47							where id = @prev
48						end
49						set @prev = @listId
50						set @curr = (select next from Clister where id = @curr)
51						if @first = null
52							set @first = @lastId
53						waitfor delay '00:00:05'
54						commit
55						break
56					end try
57					begin catch
58						rollback transaction
59						continue
60						end catch
61					end
62				end
63			end
64		end
65
66		insert into File
67		values (@fileId + "copy", @first)
68	end