uk.ac.starlink.table.join

Class JoinType

java.lang.Object

uk.ac.starlink.table.join.JoinType

public abstract class JoinType
extends Object

Defines how a set of matched rows from input tables (RowLink objects) are used to select rows for inclusion in an output table which represents the result of the matching operation. This corresponds to the type of the join in database terminology, though the naming of the instances of this class do not follow that terminology (left outer join etc), and the options here present a more complete set.

Instances of this class are available as public static members of it. Currently, these instances should only be used with the results of pair matches (ones involving exactly two tables).

Since:

5 Sep 2005

Author:

Mark Taylor

Field Summary

Fields

Modifier and Type	Field and Description
static JoinType	_1AND2 Selects only rows with input from both input tables.
static JoinType	_1NOT2 Selects only rows in the first input table which are not matched by any row in the second input table.
static JoinType	_1OR2 Selects rows with input from either or both input tables.
static JoinType	_1XOR2 Selects only rows with input from exactly one of the two input tables.
static JoinType	_2NOT1 Selects only rows in the second input table which are not matched by any row in the first input table.
static JoinType	_ALL1 Selects all output rows with input from the first input table.
static JoinType	_ALL2 Selects all output rows with input from the second input table.

Method Summary

Modifier and Type	Method and Description
abstract String	getDescription() Returns a short textual description of this type.
String	getName() Returns the name of this type.
static JoinType[]	getPairTypes() Returns a list of all the known types which apply to two-table matches.
abstract boolean	getUsedMatchFlag() Returns a value which indicates whether the matchScore is ever non-empty in the output table.
abstract boolean[]	getUsedTableFlags() Returns an array of flags indicating whether each of the tables in the input will ever have non-empty rows in the output.
abstract LinkSet	processLinks(LinkSet links, int[] rowCounts) Turns a set of links which represent matches from the matching operation into a set of links which represent the rows to output.
String	toString() Returns the name of this type.

Methods inherited from class java.lang.Object

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

Field Detail

_1AND2

public static final JoinType _1AND2

Selects only rows with input from both input tables.

_1OR2

public static final JoinType _1OR2

Selects rows with input from either or both input tables.

_ALL1

public static final JoinType _ALL1

Selects all output rows with input from the first input table.

_ALL2

public static final JoinType _ALL2

Selects all output rows with input from the second input table.

_2NOT1

public static final JoinType _2NOT1

Selects only rows in the second input table which are not matched by any row in the first input table.

_1NOT2

public static final JoinType _1NOT2

Selects only rows in the first input table which are not matched by any row in the second input table.

_1XOR2

public static final JoinType _1XOR2

Selects only rows with input from exactly one of the two input tables.

Method Detail

processLinks

public abstract LinkSet processLinks(LinkSet links,
                                     int[] rowCounts)

Turns a set of links which represent matches from the matching operation into a set of links which represent the rows to output. links is a set of RowLink objects; if the matching operation was between two tables, each element will represent a pair match (have two RowRefs, with table indices of 0 and 1 respectively). The ordering of links may influence the order of the returned collection. links may be modified by this method, and the returned value may or may not be the same object as the input links itself.

Parameters:

links - set of RowLinks representing actual matches

rowCounts - numbers of rows in the tables on which the match was performed

Returns:

set of RowLinks representing rows for the output table

getUsedTableFlags

public abstract boolean[] getUsedTableFlags()

Returns an array of flags indicating whether each of the tables in the input will ever have non-empty rows in the output.

Returns:

2-element boolean array indicating whether first and second input tables appear in output

getUsedMatchFlag

public abstract boolean getUsedMatchFlag()

Returns a value which indicates whether the matchScore is ever non-empty in the output table.

Returns:

true iff the matchScore may be used in the output

getName

public String getName()

Returns the name of this type.

Returns:

name

getDescription

public abstract String getDescription()

Returns a short textual description of this type.

Returns:

description

toString

public String toString()

Returns the name of this type.

Overrides:

toString in class Object

getPairTypes

public static JoinType[] getPairTypes()

Returns a list of all the known types which apply to two-table matches.

Returns:

array of the 7 known types