org.apache.calcite.rel.metadata

Interface BuiltInMetadata.ColumnOrigin

All Superinterfaces:

Metadata

Enclosing class:

BuiltInMetadata

public static interface BuiltInMetadata.ColumnOrigin
extends Metadata

Metadata about the origins of columns.

Method Summary

Methods

Modifier and Type	Method and Description
Set<RelColumnOrigin>	getColumnOrigins(int outputColumn) For a given output column of an expression, determines all columns of underlying tables which contribute to result values.

Methods inherited from interface org.apache.calcite.rel.metadata.Metadata

rel

Method Detail

getColumnOrigins

Set<RelColumnOrigin> getColumnOrigins(int outputColumn)

For a given output column of an expression, determines all columns of underlying tables which contribute to result values. An output column may have more than one origin due to expressions such as Union and LogicalProject. The optimizer may use this information for catalog access (e.g. index availability).

Parameters:

outputColumn - 0-based ordinal for output column of interest

Returns:

set of origin columns, or null if this information cannot be determined (whereas empty set indicates definitely no origin columns at all)