java.lang.Object
- org.apache.calcite.rel.rules.PruneEmptyRules

```
public abstract class PruneEmptyRules
extends java.lang.Object
```
Collection of rules which remove sections of a query plan known never to produce any rows.
Conventionally, the way to represent an empty relational expression is with a Values that has no tuples.

See Also:

LogicalValues.createEmpty(org.apache.calcite.plan.RelOptCluster, org.apache.calcite.rel.type.RelDataType)

Nested Class Summary

Nested Classes
Modifier and Type Class Description

static class PruneEmptyRules.RemoveEmptySingleRule
Planner rule that converts a single-rel (e.g.

Field Summary

Fields
Modifier and Type	Field	Description
`static RelOptRule`	`AGGREGATE_INSTANCE`	Rule that converts an `Aggregate` to empty if its child is empty.
`static RelOptRule`	`FILTER_INSTANCE`	Rule that converts a `LogicalFilter` to empty if its child is empty.
`static RelOptRule`	`INTERSECT_INSTANCE`	Rule that converts a `LogicalIntersect` to empty if any of its children are empty.
`static RelOptRule`	`JOIN_LEFT_INSTANCE`	Rule that converts a `Join` to empty if its left child is empty.
`static RelOptRule`	`JOIN_RIGHT_INSTANCE`	Rule that converts a `Join` to empty if its right child is empty.
`static RelOptRule`	`MINUS_INSTANCE`	Rule that removes empty children of a `LogicalMinus`.
`static RelOptRule`	`PROJECT_INSTANCE`	Rule that converts a `LogicalProject` to empty if its child is empty.
`static RelOptRule`	`SORT_FETCH_ZERO_INSTANCE`	Rule that converts a `Sort` to empty if it has `LIMIT 0`.
`static RelOptRule`	`SORT_INSTANCE`	Rule that converts a `Sort` to empty if its child is empty.
`static RelOptRule`	`UNION_INSTANCE`	Rule that removes empty children of a `LogicalUnion`.

Constructor Summary

Constructors
Constructor Description

PruneEmptyRules()

Method Summary

All Methods Static Methods Concrete Methods
Modifier and Type Method Description

private static boolean isEmpty(RelNode node)
- Methods inherited from class java.lang.Object
  clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

- Field Detail
  - UNION_INSTANCE
```
public static final RelOptRule UNION_INSTANCE
```
    Rule that removes empty children of a LogicalUnion.
    Examples:
    
    Union(Rel, Empty, Rel2) becomes Union(Rel, Rel2)
    Union(Rel, Empty, Empty) becomes Rel
    Union(Empty, Empty) becomes Empty
  - MINUS_INSTANCE
```
public static final RelOptRule MINUS_INSTANCE
```
    Rule that removes empty children of a LogicalMinus.
    Examples:
    
    Minus(Rel, Empty, Rel2) becomes Minus(Rel, Rel2)
    Minus(Empty, Rel) becomes Empty
  - INTERSECT_INSTANCE
```
public static final RelOptRule INTERSECT_INSTANCE
```
    Rule that converts a LogicalIntersect to empty if any of its children are empty.
    Examples:
    
    Intersect(Rel, Empty, Rel2) becomes Empty
    Intersect(Empty, Rel) becomes Empty
  - PROJECT_INSTANCE
```
public static final RelOptRule PROJECT_INSTANCE
```
    Rule that converts a LogicalProject to empty if its child is empty.
    Examples:
    
    Project(Empty) becomes Empty
  - FILTER_INSTANCE
```
public static final RelOptRule FILTER_INSTANCE
```
    Rule that converts a LogicalFilter to empty if its child is empty.
    Examples:
    
    Filter(Empty) becomes Empty
  - SORT_INSTANCE
```
public static final RelOptRule SORT_INSTANCE
```
    Rule that converts a Sort to empty if its child is empty.
    Examples:
    
    Sort(Empty) becomes Empty
  - SORT_FETCH_ZERO_INSTANCE
```
public static final RelOptRule SORT_FETCH_ZERO_INSTANCE
```
    Rule that converts a Sort to empty if it has LIMIT 0.
    Examples:
    
    Sort(Empty) becomes Empty
  - AGGREGATE_INSTANCE
```
public static final RelOptRule AGGREGATE_INSTANCE
```
    Rule that converts an Aggregate to empty if its child is empty.
    Examples:
    
    Aggregate(key: [1, 3], Empty) → Empty
    Aggregate(key: [], Empty) is unchanged, because an aggregate without a GROUP BY key always returns 1 row, even over empty input
    See Also:
    
    AggregateValuesRule
  - JOIN_LEFT_INSTANCE
```
public static final RelOptRule JOIN_LEFT_INSTANCE
```
    Rule that converts a Join to empty if its left child is empty.
    Examples:
    
    Join(Empty, Scan(Dept), INNER) becomes Empty
  - JOIN_RIGHT_INSTANCE
```
public static final RelOptRule JOIN_RIGHT_INSTANCE
```
    Rule that converts a Join to empty if its right child is empty.
    Examples:
    
    Join(Scan(Emp), Empty, INNER) becomes Empty
- Constructor Detail
  - PruneEmptyRules
```
public PruneEmptyRules()
```
- Method Detail
  - isEmpty
```
private static boolean isEmpty(RelNode node)
```

Class PruneEmptyRules

Nested Class Summary

Field Summary

Constructor Summary

Method Summary

Methods inherited from class java.lang.Object

Field Detail

UNION_INSTANCE

MINUS_INSTANCE

INTERSECT_INSTANCE

PROJECT_INSTANCE

FILTER_INSTANCE

SORT_INSTANCE

SORT_FETCH_ZERO_INSTANCE

AGGREGATE_INSTANCE

JOIN_LEFT_INSTANCE

JOIN_RIGHT_INSTANCE

Constructor Detail

PruneEmptyRules

Method Detail

isEmpty