On 30/08/18 09:51, Randall Smith wrote: > is how to convert existing data from one DB format to another, given some > arbitrary set of changes in the database schema in the interim.
I use SQLite's user pragma. It starts at zero. https://sqlite.org/pragma.html#pragma_user_version My code ends up looking like this: if user_version==0: CREATE TABLE IF NOT EXISTS events(key, time, message); PRAGMA user_version=1; if user_version==1: CREATE INDEX IF NOT EXISTS [events:message] ON events(message); PRAGMA user_version=2; if user_version==2: ALTER TABLE events ADD COLUMN severity; PRAGMA user_version=3; This ensures that the currently running code will upgrade the schema as needed. Ensure the commands are wrapped in a transaction so they either completely happen or not. I am helped by having low complexity schemas. If yours are large you could probably generate something like the above. Some ORM style engines also have schema and data upgrade functionality. Roger
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