public interface RelationalOperators
Modifier and Type | Field and Description |
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static RelationalOperators |
DUMMY |
Modifier and Type | Method and Description |
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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.
|
static final RelationalOperators DUMMY
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 expressionRelation 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 namesRelation 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