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DescribeDeltaHistory Unary Logical Operator

DescribeDeltaHistory is a DeltaCommand that represents DESCRIBE HISTORY SQL command.

DescribeDeltaHistory is resolved into a DescribeDeltaHistoryCommand at analysis.

DescribeDeltaHistory is a unary logical operator (Spark SQL).

Note

There's a comment in the source code of DescribeDeltaHistory that says:

A logical placeholder for describing a Delta table's history, so that the history can be leveraged in subqueries.

It is not available in the OSS version of Delta Lake, though. Sorry 🤷

Creating Instance

DescribeDeltaHistory takes the following to be created:

  • Child LogicalPlan (Spark SQL)
  • History Limit
  • Output Schema Attributes

DescribeDeltaHistory is created using apply factory method.

Creating DescribeDeltaHistory

apply(
  path: Option[String],
  tableIdentifier: Option[TableIdentifier],
  limit: Option[Int]): DescribeDeltaHistory

apply creates a DescribeDeltaHistory with a UnresolvedDeltaPathOrIdentifier (with the given path and tableIdentifier).

apply is used for:

toCommand

toCommand: DescribeDeltaHistoryCommand

toCommand converts this DescribeDeltaHistory logical operator into a DescribeDeltaHistoryCommand executable command.

toCommand is used when:

  • DeltaAnalysis logical resolution rule is executed (to resolve a DescribeDeltaHistory logical operator)