How to rollback non linear migrations in django?-CodePudding

Suppose I have following migrations in Django.

    X
  /   \
 A      B      [A and B can represent any number of linear migrations.] 
  \   /
    Y (merge migration).

Doing python manage.py migrate app X will unapply all of A, B and Y. How can I unapply only B and Y?. And keep A as it is, i.e applied.

CodePudding user response：

    X(*)      [* represent migration has been applied.]
  /   \
 A(*)   B(*)  [A and B can represent any number of linear migrations.] 
  \   /
    Y(*)      (merge migration)

Steps to unapply only one path i.e B and Y

Unapply only Y. By doing python manage.py migrate app B (or A; both works).
```
   X(*)     
 /    \
A(*)   B(*) 
 \    /
   Y()   
```
Remove the migration files A and Y for time being from the project location.
```
  X(*)     
   \
    B(*) 
```
Now unapply B, by doing python manage.py migrate app X.
```
  X(*)     
   \
    B() 
```
Bring the migration files A and Y to the original location. You can now safely delete the unapplied migrations B and Y, if you wish to.
```
  X(*)     
 /   \
A(*)  B() 
 \   /
   Y()   
```

The gist is, django can only rollback migrations if the files are present in the location. If you do not want to rollback a migration path (i.e A here), remove it from the project location while performing rollback.