Clojurians Log v2
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datalevin
Ahmed Hassan 2024-12-15T14:36:05.780289Z
How do we do schema migrations in Datalevin?
Ahmed Hassan 2024-12-15T14:47:14.594729Z
it seems like datalevin.core/update-schema does this?
Huahai 2024-12-15T16:43:37.667239Z
yes. As long as the schema migration does not require data changes, it is supported.
Ahmed Hassan 2024-12-15T19:13:30.594029Z
what are examples of data changes?
Huahai 2024-12-15T19:21:27.726519Z
for example, you want to change a data type from long to string. But your data is already in the DB with longs. That's not supported right now. Such migration is on the roadmap.
👍 1
Huahai 2024-12-15T19:24:53.985029Z
Right now, these three types of changes are not supported (when data is already populated): 1 cardinality change from many to one 2. data type changes as mentioned above 3. uniqueness change when data is already not unique
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Huahai 2024-12-15T19:26:07.370869Z
Attempting to do these will throw exception.
Huahai 2024-12-15T19:27:37.034699Z
In the future, we can support such migration by asking user to specify how they want to do these changes. Probably by specifying a function, etc. TBD.
Huahai 2024-12-15T19:36:43.862429Z
Right now, any schema changes that are consistent with existing data is supported, e.g. rename an attribute, delete unused attribute, add attribute, etc.
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