Record file sizes in db

Moderation interface is going to use this.

migrations/versions/30bfe33aa328_add_file_size_field.py

@@ -0,0 +1,46 @@
+"""add file size field
+
+Revision ID: 30bfe33aa328
+Revises: 5cee97aab219
+Create Date: 2022-12-13 22:32:12.242394
+
+"""
+
+# revision identifiers, used by Alembic.
+revision = '30bfe33aa328'
+down_revision = '5cee97aab219'
+
+from alembic import op
+import sqlalchemy as sa
+from sqlalchemy.ext.automap import automap_base
+from sqlalchemy.orm import Session
+from flask import current_app
+from pathlib import Path
+
+Base = automap_base()
+
+def upgrade():
+    op.add_column('file', sa.Column('size', sa.BigInteger(), nullable=True))
+    bind = op.get_bind()
+    Base.prepare(autoload_with=bind)
+    File = Base.classes.file
+    session = Session(bind=bind)
+
+    storage = Path(current_app.config["FHOST_STORAGE_PATH"])
+
+    updates = []
+    files = session.scalars(sa.select(File).where(sa.not_(File.removed)))
+    for f in files:
+        p = storage / f.sha256
+        if p.is_file():
+            updates.append({
+                "id" : f.id,
+                "size" : p.stat().st_size
+            })
+
+    session.bulk_update_mappings(File, updates)
+    session.commit()
+
+
+def downgrade():
+    op.drop_column('file', 'size')