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public interface RelationalOperators
Field Summary | |
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static RelationalOperators |
DUMMY
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Method Summary | |
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Relation |
project(Set<? extends ProjectionSpec> projectionSpecs)
Applies the projection operator to this relation. |
Relation |
renameColumns(ColumnRenamer renamer)
Applies the rename operator to this relation. |
Relation |
select(Expression condition)
Applies the selection operator to this relation. |
Field Detail |
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static final RelationalOperators DUMMY
Method Detail |
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Relation select(Expression condition)
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.
condition
- A boolean expression
Relation renameColumns(ColumnRenamer renamer)
Applies the rename operator to this relation.
Renames of attributes that don't exist in the relation are ignored.
renamer
- A map from original to replacement names
Relation project(Set<? extends ProjectionSpec> projectionSpecs)
Applies the projection operator to this relation.
The new relation will contain only the attributes given as the argument.
projectionSpecs
- A set of ProjectionSpec
instances
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