forked from 3wordchant/capsul-flask
correctly handle when the desiredSchemaVersion < schemaVersion
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@ -7,10 +7,12 @@ Python Flask web application for capsul.org
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capsulflask has a concept of a schema version. When the application starts, it will query the database for a table named
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`schemaversion` that has one row and one column (`version`). If the `version` it finds is not equal to the `desiredSchemaVersion` variable set in `db.py`, it will run migration scripts from the `schema_migrations` folder one by one until the `schemaversion` table shows the correct version.
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For example, the script named `02_up_xyz.sql` should contain code that migrates the database in a reverse-able fashion from schema version 1 to schema version 2. Likewise, the script `02_down_xyz.sql` should contain code that migrates from schema version 2 back to schema version 1.
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For example, the script named `02_up_xyz.sql` should contain code that migrates the database from schema version 1 to schema version 2. Likewise, the script `02_down_xyz.sql` should contain code that migrates from schema version 2 back to schema version 1.
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**IMPORTANT: if you need to make changes to the schema, make a NEW schema version. DO NOT EDIT the existing schema versions.**
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In general, for safety, schema version upgrades should not delete data. Schema version downgrades will simply throw an error and exit for now.
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## how to run locally
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Ensure you have the pre-requisites for the psycopg2 Postgres database adapter package
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