feat(6845): every instance has an id lineage, and every full backup carries it

instance_identity is one row made by migration 0127 with a random id, so an instance has it before its first account. A full backup carries it in its header as instance_id (the tar manifest header and the JSON top level); BACKUP_VERSION is 28. The table rides in _NOT_INCLUDED: a restore decides from the header value rather than copying a row. Two stores with the same id number their rows the same way. That is what lets a later step roll a live instance back by original id, refuse a backup whose ids would land on unrelated rows, and have a fresh-instance restore adopt the backup's id (adopt_instance_id). Milestone 582, step 1. Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
2026-11-04 19:53:45 -05:00
parent 3c01e17559
commit 6d8db0bb65
7 changed files with 171 additions and 4 deletions
@@ -0,0 +1,39 @@
+"""instance identity — the id lineage a backup carries
+
+Revision ID: 0127
+Revises: 0126
+Create Date: 2026-11-05
+
+One row naming this database's id lineage. Every full backup carries it, a
+restore into a fresh instance adopts it (the restore keeps the original ids),
+and rolling a live instance back requires the backup's to match, so a backup's
+ids never land on unrelated rows. Made here with a random value, so every
+instance has one before its first account exists.
+"""
+import sqlalchemy as sa
+from alembic import op
+
+revision = "0127"
+down_revision = "0126"
+branch_labels = None
+depends_on = None
+
+
+def upgrade() -> None:
+    op.create_table(
+        "instance_identity",
+        sa.Column("id", sa.Integer(), primary_key=True),
+        sa.Column("instance_id", sa.Text(), nullable=False),
+        sa.Column(
+            "created_at", sa.DateTime(timezone=True), nullable=False,
+            server_default=sa.func.now(),
+        ),
+        sa.CheckConstraint("id = 1", name="ck_instance_identity_single_row"),
+    )
+    op.execute(
+        "INSERT INTO instance_identity (id, instance_id) VALUES (1, gen_random_uuid()::text)"
+    )
+
+
+def downgrade() -> None:
+    op.drop_table("instance_identity")