Schema Contract

2 probes

Validates dataset schemas against a declared YAML contract and detects schema drift over time. Contracts specify column names, data types, nullable flags, and ordering. Drift detection compares the live schema against the last known baseline and emits CheckResult alerts for added, removed, or type-changed columns.

Configuration

sources:
  - type: schema_contract
    dataset_path: /data/curated/orders.parquet
    contract: /etc/metapod/contracts/orders.yaml
    fail_on_drift: true

Contract file example:

# /etc/metapod/contracts/orders.yaml
dataset: orders
columns:
  - name: order_id
    type: int64
    nullable: false
  - name: customer_email
    type: string
    nullable: true
  - name: amount
    type: float64
    nullable: false

Probes

Probe	Description
`schema_contract.quality.validate`	Validate live schema against YAML contract (missing/extra/mistyped columns)
`schema_contract.quality.drift`	Detect schema drift vs. last recorded baseline

Usage

metapod run "schema_contract.quality.*" --config config.yaml

Output

{
  "probe": "schema_contract.quality.validate",
  "source": "schema_contract",
  "collected_at": "2026-03-31T08:00:00Z",
  "results": [
    {
      "dataset": "orders.parquet",
      "contract": "orders.yaml",
      "status": "fail",
      "violations": [
        {
          "column": "amount",
          "expected_type": "float64",
          "actual_type": "string",
          "issue": "type_mismatch"
        }
      ]
    }
  ]
}