ssdt: change the types of primary key/secondary keys - sql-server-data-tools

Question

Original table1 and Table2. Both tables has data.
CREATE TABLE [dbo].[Table1]
(
[Id] int NOT NULL PRIMARY KEY
)
CREATE TABLE [dbo].[Table2]
(
[Id] INT NOT NULL PRIMARY KEY,
[Table1Id] Int NULL,
Constraint [FK_Table1_Table2] foreign key ([Table1Id]) references [Table1] (Id)
)
I'd like to change the Table1.Id to UNIQUEIDENTIFIER.
Obviously just jump in and change the type from int to UNIQUEIDENTIFIER for Table1.Id and 'Table2.Table1Id'. Then Publish. Here is the code:
CREATE TABLE [dbo].[tmp_ms_xx_Table1] (
[Id] UNIQUEIDENTIFIER NOT NULL,
PRIMARY KEY CLUSTERED ([Id] ASC)
);
IF EXISTS (SELECT TOP 1 1
FROM [dbo].[Table1])
BEGIN
INSERT INTO [dbo].[tmp_ms_xx_Table1] ([Id])
SELECT [Id]
FROM [dbo].[Table1]
ORDER BY [Id] ASC;
END
This code will fail because original Table1.Id is Int while temp table Id is UNIQUEIDENTIFIER.
Then, I try to with Pre-Scripts. Ideally all the changes will be done manually.
--drop fk constraint
alter table [Table2] drop constraint [FK_Table1_Table2];
--rename table1.id
exec sp_rename 'Table1.Id', 'Id2', 'COLUMN';
alter table [Table1] add Id uniqueidentifier not null
default newid();
--rename table2.table1id
exec sp_rename 'Table2.Table1Id', 'Table1Id2', 'COLUMN';
alter table [Table2] add Table1Id uniqueidentifier null;
update t2 set t2.Table1ID = t1.Id
from Table2 t2 left join Table1 t1 on t2.Table1Id2 = t1.Id2;
alter table [Table2] add constraint [FK_Table1_Table2] foreign key (Table1Id) references Table1 (Id);
However it FAIL again as SSDT is trying to compare its data structure again the target database.
Any idea please?

Answer 1

You're right. The problem is that you can't include schema changes in the pre-deployment script because SSDT's deployment script is generated prior to your schema changes. It is therefore only useful for data-only changes.
The solution is to do this outside of the SSDT process altogether. Yes, it's a pre-pre-deployment script! Essentially you have to apply your change by yourself before you even get to the SSDT bit.
(There's probably a way to do this via a custom deployment contributor. After all, everything is possible in code...)
Can I convince you to take a look at a migration-based solution as it appears that you have sufficient need for an element of fine-grained script "customisation". DBUp is a popular open source solution. ReadyRoll is a more-integrated commercial solution that shares a lot with SSDT.

Answer 2

the problem is the old data. it will be ok without the data in table in step 2.
1.pre-script: copy/process old data to temp tables, delete them from original tables
create table #table1 (
id int null,
id2 uniqueidentifier null
);
insert into #table1 (id,id2)
select id,newid() from Table1;
create table #table2 (
id int null,
table1id int null,
table1id2 uniqueidentifier null
);
insert into #table2 (id, table1id)
select id,table1id from Table2;
update t2 set t2.table1id2=t1.id2
from #table2 t2 left join #table1 t1 on t2.table1id = t1.id;
delete from table2;
delete from table1;
dacpac will auto generate the changes for schema. it will be ok because no data is existing any more.
post-script: insert data back from temp tables in pre-script:
insert into table1 (id)
select id2 from #table1;
insert into table2 (id,table1id)
select id, table1id2 from #table2;