Invariants Utility¶

delta.invariants¶

Invariants defines delta.invariants for the column invariants of a delta table.

delta.invariants contains a JSON-encoded SQL expression.

Extracting Constraints from Schema¶

getFromSchema(
  schema: StructType,
  spark: SparkSession): Seq[Constraint]

getFromSchema finds columns (top-level or nested) that are non-nullable and have delta.invariants metadata.

For every parent of the columns, getFromSchema creates NotNull constraints.

For the columns themselves, getFromSchema creates Check constraints.

getFromSchema is used when:

• Constraints utility is used to extract table constraints
• Protocol utility is used to determine the required minimum protocol

Rule¶

Invariants utility defines a Rule abstraction.

Rule has a name.

ArbitraryExpression¶

ArbitraryExpression is a Rule with the following:

• EXPRESSION([expression]) name
• An Expression (Spark SQL)