resetting-the-database.md

Resetting the database

Clear the stored data, but keep the database structure

Backscope caches data about every sequence that's been requested. You may find yourself in a situation where that stored data is causing a problem. For example:

• You're working on code that only runs when Backscope downloads data from the OEIS. To try your code on a particular sequence, you need to make sure the sequence isn't cached already.
• A bug in your code has left certain data flagged, incorrectly, as a download in progress. Backscope won't clear the flag until the download finishes, and it won't start the download if the flag is set.

In a situation like this, you don't need to wipe out the whole database structure; it's enough to clear the data stored inside that structure. Here's how to do it:

1. Activate Backscope's virtual environment, if it's not active already.
   • For example, if you're using venv and you've put the virtual environment in .venv, call source .venv/bin/activate.
2. Clear the database by calling flask clear-database.

⚠️ Beware: this will clear the database named by the POSTGRES_DB variable in the .env file.

Wipe out the whole database structure and build a fresh database from scratch

More rarely, you may find yourself in a situation where the structure of the database is causing a problem, which can't be solved just by clearing the contents of the database. For example:

• You just wrote or checked out a version of Backscope that uses a different database schema.

In a situation like this, it's often easiest to wipe out the whole database structure and build a new database from scratch, as if you're setting up Backscope for the first time. Here's how to do it:

1. Activate Backscope's virtual environment, if it's not active already.
   • For example, if you're using venv and you've put the virtual environment in .venv, call source .venv/bin/activate.
2. Erase every trace of the database from your global PostgreSQL instance by calling:

   dropdb <database name>

   Typically, <database name> should match the POSTGRES_DB variable in the .env file.
3. Forget local information about past migrations by removing or renaming the migrations folder in the top level of the Backscope repository.
   • For example, put migrations in the trash by calling gio trash migrations on Ubuntu 18.04 or newer.
4. Create a new database and furnish it with the Backscope database structure by calling:

   createdb <database name>
   flask db init
   flask db migrate
   flask db upgrade

⚠️ Beware: steps 2–3 will wipe out the entire structure and contents of the database <database name>.