Package uk.ac.starlink.table.join
Class JoinType
- java.lang.Object
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- uk.ac.starlink.table.join.JoinType
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public abstract class JoinType extends java.lang.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
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Field Summary
Fields Modifier and Type Field 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.
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Method Summary
All Methods Static Methods Instance Methods Abstract Methods Concrete Methods Modifier and Type Method Description abstract java.lang.String
getDescription()
Returns a short textual description of this type.java.lang.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.java.lang.String
toString()
Returns the name of this type.
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Field Detail
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_1AND2
public static final JoinType _1AND2
Selects only rows with input from both input tables.
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_1OR2
public static final JoinType _1OR2
Selects rows with input from either or both input tables.
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_ALL1
public static final JoinType _ALL1
Selects all output rows with input from the first input table.
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_ALL2
public static final JoinType _ALL2
Selects all output rows with input from the second input table.
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_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.
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_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.
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_1XOR2
public static final JoinType _1XOR2
Selects only rows with input from exactly one of the two input tables.
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Method Detail
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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 ofRowLink
objects; if the matching operation was between two tables, each element will represent a pair match (have twoRowRef
s, with table indices of 0 and 1 respectively). The ordering oflinks
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 inputlinks
itself.- Parameters:
links
- set of RowLinks representing actual matchesrowCounts
- numbers of rows in the tables on which the match was performed- Returns:
- set of RowLinks representing rows for the output table
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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
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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
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getName
public java.lang.String getName()
Returns the name of this type.- Returns:
- name
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getDescription
public abstract java.lang.String getDescription()
Returns a short textual description of this type.- Returns:
- description
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toString
public java.lang.String toString()
Returns the name of this type.- Overrides:
toString
in classjava.lang.Object
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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
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