AlterDeltaTableCommand¶

AlterDeltaTableCommand is an extension of the DeltaCommand abstraction for Delta commands that alter a DeltaTableV2.

Contract¶

table¶

table: DeltaTableV2

DeltaTableV2

Used when:

AlterDeltaTableCommand is requested to startTransaction

Implementations¶

startTransaction¶

startTransaction(): OptimisticTransaction

startTransaction simply requests the DeltaTableV2 for the DeltaLog that in turn is requested to startTransaction.

Checking Dependent Expressions¶

checkDependentExpressions(
  sparkSession: SparkSession,
  columnParts: Seq[String],
  newMetadata: actions.Metadata,
  protocol: Protocol,
  operationName: String): Unit

checkDependentExpressions skips execution when spark.databricks.delta.alterTable.changeColumn.checkExpressions configuration property is disabled (false).

checkDependentExpressions checks if the column to change (columnParts) is referenced by check constraints or generated columns (and throws an AnalysisException if there are any).

checkDependentExpressions is used when:

AlterTableDropColumnsDeltaCommand and AlterTableChangeColumnDeltaCommand are executed

Check Constraints¶

checkDependentExpressions findDependentConstraints (with the givencolumnParts and the newMetadata) and throws an AnalysisException if there are any:

Cannot [operationName] column [columnName] because this column is referenced by the following check constraint(s):
    [constraints]

Generated Columns¶

checkDependentExpressions findDependentGeneratedColumns (with the givencolumnParts, the newMetadata and protocol) and throws an AnalysisException if there are any:

Cannot [operationName] column [columnName] because this column is referenced by the following generated column(s):
    [fieldNames]