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### Why direction of migration is required Imagine this steps: V1 | V2 | V3 --- | --- | --- X | Y:RX | X Where `X` is column name, `Y:RX` is column with `Y` name and `reanmed_from` property set to `X` name. ### What happens when we generate migration scripts Migration | Diff result `[src, tar]` | Description --- | --- | --- v1 -> v2 | X, Y:RX | This works well. The `X` was renamed to `Y`. v2 -> v3 | Y:RX, X | This is also expected. The `Y` was dropped and `X` was created. v2 -> v1 | Y:RX, X | For downgrade script it is not expected that `Y` will be dropped and `X` will be created from scratch. During migration `v1->v2` it was renamed and now durint `v2->v1` we expect it should be renamed back. But this drop happens because it works as designed for `upgrade` direction. But this scenario it is `downgrade`. Unfortunately We can not detect this automatically: the order of `[src, dst]` is the same and the set of `extra` properties are the same. (For now I am skipping more complex scenarios when `v3` migration has columns with created and/or renamed names similar to `v2` version and its consequences on `v1`) ### Proposition From the above to get the expected result during `downgrades` we need to pass the direction that the `downgrade` migration should be generated.
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Why direction of migration is required
Imagine this steps:
Where
Xis column name,Y:RXis column withYname andreanmed_fromproperty set toXname.What happens when we generate migration scripts
[src, tar]Xwas renamed toY.Ywas dropped andXwas created.Ywill be dropped andXwill be created from scratch. During upgrade migrationv1->v2it was renamed and now during downgradev2->v1we expect it should be renamed back. But instead the drop happens because it works as designed forupgradedirection. But this scenario it isdowngrade. Unfortunately We can not detect this automatically: the order of[src, dst]is the same and the set ofextraproperties are the same.Proposition
From the above to get the expected result during
downgradeswe need to pass the flag that thedowngrademigration should be generated.