ShowDeltaTableColumnsCommand Unary Logical Operator¶

ShowDeltaTableColumnsCommand is a DeltaCommand that represents a ShowColumns (Spark SQL) logical command in an analyzed logical query plan after DeltaAnalysis.

SHOW COLUMNS
  (FROM | IN) [table]
  ((FROM | IN) [namespace])?

ShowDeltaTableColumnsCommand is a RunnableCommand (Spark SQL).

ShowColumnsCommand in Spark SQL

ShowDeltaTableColumnsCommand is a Delta Lake-specific variant of ShowColumnsCommand from Spark SQL.

Creating Instance¶

ShowDeltaTableColumnsCommand takes the following to be created:

Child logical operator with a delta table

ShowDeltaTableColumnsCommand is created when:

DeltaAnalysis is requested to resolve ShowColumns logical operator (over a resolved DeltaTableV2)

Child Logical Operator with Delta Table¶

ShowDeltaTableColumnsCommand is given a ResolvedTable (Spark SQL) with a DeltaTableV2 when created.

Executing Command¶

RunnableCommand

run(
  sparkSession: SparkSession): Seq[Row]

run is part of the RunnableCommand (Spark SQL) abstraction.

run requests the DeltaLog (of the delta table) to update.

run returns the field names of the schema of the delta table.