uk.ac.starlink.ttools.task

Class CombinedColumn

java.lang.Object

uk.ac.starlink.ttools.task.CombinedColumn

public class CombinedColumn
extends Object

Describes an output column formed by aggregation of values from an input expression.

Since:

21 Dec 2021

Author:

Mark Taylor

Constructor Summary

Constructors

Constructor and Description
CombinedColumn(String expr, Combiner combiner, String name) Constructor.

Method Summary

Modifier and Type	Method and Description
static StringMultiParameter	createCombinedColumnsParameter(String name, CombinerParameter dfltCombinerParam) Creates a parameter for specifying aggregate columns.
Combiner	getCombiner() Returns the aggregation method.
String	getExpression() Returns the expression to be aggregated.
String	getName() Returns the output column name.
static CombinedColumn	parseSpecification(Environment env, String txt, Parameter<?> txtParam, CombinerParameter combinerParam) Parses an input expression to a CombinedColumn value.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Detail

CombinedColumn

public CombinedColumn(String expr,
                      Combiner combiner,
                      String name)

Constructor.

Parameters:

expr - expression to be aggregated

combiner - aggregation method, may be null to indicate default

name - name of output column, may be null to indicate default

Method Detail

getExpression

public String getExpression()

Returns the expression to be aggregated.

Returns:

input column name or expression, not null

getCombiner

public Combiner getCombiner()

Returns the aggregation method.

Returns:

aggregation method, or null to indicate default

getName

public String getName()

Returns the output column name.

Returns:

output name, or null to indicate default

parseSpecification

public static CombinedColumn parseSpecification(Environment env,
                                                String txt,
                                                Parameter<?> txtParam,
                                                CombinerParameter combinerParam)
                                         throws ParameterValueException

Parses an input expression to a CombinedColumn value.

Parameters:

env - execution environment

txt - input expression

txtParam - parameter supplying input value, used for reference in thrown exceptions

combinerParam - parameter supplying combiner values, used to decode combiner specifications

Throws:

ParameterValueException

createCombinedColumnsParameter

public static StringMultiParameter createCombinedColumnsParameter(String name,
                                                                  CombinerParameter dfltCombinerParam)

Creates a parameter for specifying aggregate columns. The parameter return value is an array of strings, each of which can be parsed using the parseSpecification method.

Parameters:

name - parameter name

dfltCombinerParam - parameter used for specifying default aggregation method, used in documentation