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java.lang.Objectde.fuberlin.wiwiss.d2rq.algebra.RelationImpl
public class RelationImpl
Field Summary |
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Fields inherited from interface de.fuberlin.wiwiss.d2rq.algebra.Relation |
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EMPTY, TRUE |
Constructor Summary | |
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RelationImpl(ConnectedDB database,
AliasMap aliases,
Expression condition,
Set joinConditions)
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Method Summary | |
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AliasMap |
aliases()
The tables that are used to set up this relation, both in their aliased form, and with their original physical names. |
Expression |
condition()
An expression that must be satisfied for all tuples in the relation. |
ConnectedDB |
database()
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Set |
joinConditions()
Returns the join conditions that must hold between the tables in the relation. |
Relation |
renameColumns(ColumnRenamer renames)
Applies the rename operator to this relation. |
Relation |
select(Expression selectCondition)
Applies the selection operator to this relation. |
Methods inherited from class java.lang.Object |
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clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait |
Constructor Detail |
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public RelationImpl(ConnectedDB database, AliasMap aliases, Expression condition, Set joinConditions)
Method Detail |
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public ConnectedDB database()
database
in interface Relation
public AliasMap aliases()
Relation
aliases
in interface Relation
public Expression condition()
Relation
condition
in interface Relation
Expression.TRUE
indicates no conditionpublic Set joinConditions()
Relation
joinConditions
in interface Relation
Join
spublic Relation select(Expression selectCondition)
RelationalOperators
Applies the selection operator to this relation. The new relation will contain only the tuples for which the expression evaluates to true.
Selection on attributes that don't exist in the relation are considered to be always false and will cause an empty relation.
select
in interface RelationalOperators
selectCondition
- A boolean expression
public Relation renameColumns(ColumnRenamer renames)
RelationalOperators
Applies the rename operator to this relation.
Renames of attributes that don't exist in the relation are ignored.
renameColumns
in interface RelationalOperators
renames
- A map from original to replacement names
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