feat: a script to backfill commitments table

mig.js

@@ -0,0 +1,63 @@
+import pg from 'pg'
+
+/*
+Usage:
+
+1. Setup port forwarding between your local computer and Postgres instance hosted by Fly.io
+  ([docs](https://fly.io/docs/postgres/connecting/connecting-with-flyctl/)). Remember to use a
+  different port if you have a local Postgres server for development!
+
+   ```sh
+   fly proxy 5454:5432 -a spark-db
+   ```
+
+2. Find spark-db entry in 1Password and get the user and password from the connection string.
+
+3. Run the following command to apply the updates, remember to replace "user" and "password"
+   with the real credentials:
+
+   ```sh
+   DATABASE_URL="postgres://user:password@localhost:5454/spark" node mig.js
+   ```
+
+*/
+
+const { DATABASE_URL } = process.env
+
+const client = new pg.Client({ connectionString: DATABASE_URL })
+await client.connect()
+
+while (true) {
+  // Step 1: find the oldest commitment (the first commitment that we don't need to backfill)
+  const { rows: [{ published_at: end }] } = await client.query(
+    'SELECT published_at FROM commitments ORDER BY published_at LIMIT 1'
+  )
+  console.log('Processing measurements reported before', end)
+
+  // Step 2: backfill commitments for the last hour before "end"
+  // Note: we may omit some older measurements belonging to the first commitment found
+  // That's ok. When the next run finds a CID already present in the commitments table,
+  // the part "ON CONFLICT DO NOTHING" will tell PG to silently ignore the INSERT command.
+  const { rows, rowCount } = await client.query(`
+  INSERT INTO commitments (cid, published_at)
+    SELECT published_as as cid, MAX(finished_at) + INTERVAL '3 minutes' as published_at FROM measurements
+    WHERE finished_at >= ($1::TIMESTAMPTZ - INTERVAL '12 hour') AND finished_at <= $1::TIMESTAMPTZ
+    GROUP BY published_as
+    ORDER BY published_at
+  ON CONFLICT DO NOTHING
+  RETURNING cid -- I _think_ this helps to get correct row count reported by PG
+`, [
+    end
+  ])
+
+  // See https://node-postgres.com/apis/result#resultrowcount-int--null
+  // The property `result.rowCount` does not reflect the number of rows returned from a
+  // query. e.g. an update statement could update many rows (so high result.rowCount value) but
+  // result.rows.length would be zero.
+  // I am not sure which value is the correct one to use, I'll update this code after I run
+  // it for the first time.
+  console.log('rowCount: %s rows.length: %s', rowCount, rows.length)
+  if (rowCount === 0) break
+}
+
+await client.end()