eschutho edited a comment on issue #12566:
URL: https://github.com/apache/superset/issues/12566#issuecomment-773689200


   @robdiciuccio I added more to the DB migration bullet points. LMK if that 
looks ok to you: 
   
   >Breaking Changes: Destructive changes in data types, structure or nullable, 
i.e., reducing varchar amount, going from bigint to int, or changing the schema 
of a json blob, making a column not null when it was previously nullable.
   
   >If a migration has a script that updates data to conform to new database 
schema, most deployment strategies will run the migration live with the 
existing code and then deploy the new code, causing downtime between when the 
migration is run and the new code is deployed. Therefore, be very cautious 
about changing database schemas. Below are some suggestions to avoid downtime:
   
   >Schema changes such as JSON blob structure, reducing varchar limits, 
changing bigint to an int or making a column not null should be treated like 
column changes. Instead of changing the data structure in the same column, 
create a new column with the new schema or structure, copy the data to the new 
structure, and then point the code to the new column. In a later major release, 
remove the old column.


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