Add migration to backfill user.pubid column

h/migrations/versions/f32200e2e496_backfill_user_pubid.py

@@ -0,0 +1,90 @@
+"""Backfill user.pubid with unique values."""
+
+import logging
+import random
+
+import sqlalchemy as sa
+from alembic import op
+from sqlalchemy.orm import declarative_base, sessionmaker
+
+revision = "f32200e2e496"
+down_revision = "3bae642f2b36"
+
+logger = logging.getLogger(__name__)
+
+USER_PUBID_LENGTH = 12
+USER_BATCH_LIMIT = 1000
+USER_MAX_COUNT = 100_000
+USER_PUBID_RETRIES = 5
+
+
+Base = declarative_base()
+
+
+class User(Base):
+    __tablename__ = "user"
+    id = sa.Column(sa.Integer, primary_key=True)
+    pubid = sa.Column(sa.String())
+
+
+def generate(length):
+    """
+    Generate a random string of the specified length.
+
+    This is the generate() function from h/pubid.py.
+    """
+    alphabet = "123456789ABDEGJKLMNPQRVWXYZabdegijkmnopqrvwxyz"
+    return "".join(random.SystemRandom().choice(alphabet) for _ in range(length))
+
+
+def backfill_users(
+    session,
+    user_batch_limit,
+    user_max_count,
+    user_pubid_retries,
+    user_pubid_length,
+):
+    user_query = (
+        session.query(User).filter(User.pubid.is_(None)).limit(user_batch_limit)
+    )
+
+    count = 0
+    while users := user_query.all():
+        if count >= USER_MAX_COUNT:
+            logger.info("Reached maximum user count of %d", user_max_count)
+            break
+        batch_count = len(users)
+        for retries in range(user_pubid_retries):
+            try:
+                for user in users:
+                    user.pubid = generate(user_pubid_length)
+                session.commit()
+                count += batch_count
+                break
+            except sa.exc.IntegrityError:
+                logger.warning(
+                    "Failed to generate unique pubids, retrying %d/%d",
+                    retries + 1,
+                    USER_PUBID_RETRIES,
+                )
+                session.rollback()
+        else:
+            raise RuntimeError(f"Failed to generate {batch_count} unique pubids")
+
+        logger.info("Back-filled %d user.pubid's", count)
+
+
+def upgrade():
+    session = sessionmaker()(bind=op.get_bind())
+
+    backfill_users(
+        session,
+        user_batch_limit=USER_BATCH_LIMIT,
+        user_max_count=USER_MAX_COUNT,
+        user_pubid_retries=USER_PUBID_RETRIES,
+        user_pubid_length=USER_PUBID_LENGTH,
+    )
+
+
+def downgrade():
+    pass