YantrikDB

Hotfix for the v0.8.13 cluster upgrade failure (yantrikos/yantrikdb-server homelab incident, 2026-05-09).

The bug

Engine 0.6.x → 0.7.2 migration tripped on duplicate column name: embedding for any deployment whose meta.schema_version had been previously rewound — e.g. by a brief rollback to an older binary against a newer on-disk DB. SQLite has no IF NOT EXISTS for ALTER TABLE ADD COLUMN, so MIGRATE_V23_TO_V24 was non-idempotent at the statement level.

The fix (two parts)

1. Idempotent migration runner. New run_migration_idempotent helper splits each migration SQL batch on ;, executes statements individually, and swallows known-safe errors:

• duplicate column name: <X> — re-running ALTER TABLE ADD COLUMN
• <X> already exists — defensive belt-and-suspenders for CREATE statements

Replaces conn.execute_batch(sql) in the migration loop. Makes every entry in the v1→v25 chain replay-safe retroactively, healing already-affected deployments without manual intervention.

2. MAX-stamp meta.schema_version. Previously open() unconditionally wrote SCHEMA_VERSION to meta — which silently downgraded the stamp if an older binary ran against a newer DB. Now writes max(existing_version, SCHEMA_VERSION). Forward-only progress on the meta stamp going forward.

Tests

Two new regression tests in engine/tests.rs:

• migration_replay_does_not_trip_on_already_present_column — reproduces the homelab failure scenario.
• migration_meta_stamp_does_not_downgrade — locks the MAX-stamp invariant.

1421 library tests pass (1419 + 2 new). Release build clean.

Upgrade path

Existing v0.6.x / v0.7.x deployments that hit the bug: pull a server build with engine ≥0.7.3. Engine open() will:

• See existing_version <= 23 (or whatever your meta got rewound to)
• Re-run V23_TO_V24 idempotently — ALTER TABLE ADD COLUMN no-ops because column exists
• Run V24_TO_V25 cleanly
• MAX-stamp meta to current SCHEMA_VERSION

No data loss, no SQL surgery, no manual fixture restoration.

Diagnosis

yantrikdb-server msg 3467c556 (homelab cluster incident, .140/.141 nodes), engine response fa070846, fix commit a5de0f2.

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