Backfill users.name from oauth_github.login

migrations/data_user_name_backfill.sql

@@ -0,0 +1,40 @@
+-- Backfill `users.name` from `oauth_github.login` for users whose `name` is
+-- still NULL. `users.name` is currently set only when the GitHub profile has
+-- a display name, so users without one have NULL there; this fills those in
+-- with the GitHub username so every account has a non-NULL name.
+--
+-- Iterates by `users.id` range and COMMITs between batches so row locks
+-- release between iterations and concurrent traffic isn't blocked. The DO
+-- block must be run outside an explicit transaction (`psql -f <file>` is
+-- fine; do NOT wrap with BEGIN/COMMIT, since COMMIT inside DO requires the
+-- block to be at the top level).
+--
+-- Idempotent: re-running the file is a no-op once every account has a name,
+-- because the UPDATE filters on `users.name IS NULL`.
+
+SET lock_timeout = '5s';
+SET statement_timeout = '60s';
+
+DO $$
+DECLARE
+    lo INT;
+    hi INT;
+    pos INT;
+    batch_size CONSTANT INT := 5000;
+BEGIN
+    SELECT MIN(id), MAX(id) INTO lo, hi FROM users WHERE name IS NULL;
+    IF lo IS NULL THEN RETURN; END IF;
+
+    pos := lo;
+    WHILE pos <= hi LOOP
+        UPDATE users
+        SET name = oauth_github.login
+        FROM oauth_github
+        WHERE oauth_github.user_id = users.id
+          AND users.name IS NULL
+          AND users.id >= pos
+          AND users.id < pos + batch_size;
+        COMMIT;
+        pos := pos + batch_size;
+    END LOOP;
+END $$;