Package org.apache.calcite.rel.rules

Class PruneEmptyRules

java.lang.Object

org.apache.calcite.rel.rules.PruneEmptyRules

public abstract class PruneEmptyRules
extends 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 interface	PruneEmptyRules.CorrelateLeftEmptyRuleConfig	Configuration for rule that prunes a correlate if its left input is empty.
static interface	PruneEmptyRules.CorrelateRightEmptyRuleConfig	Configuration for rule that prunes a correlate if its right input is empty.
static interface	PruneEmptyRules.IntersectEmptyPruneRuleConfig	Configuration for a rule that prunes an Intersect if any of its inputs is empty.
static interface	PruneEmptyRules.JoinLeftEmptyRuleConfig	Configuration for rule that prunes a join it its left input is empty.
static interface	PruneEmptyRules.JoinRightEmptyRuleConfig	Configuration for rule that prunes a join it its right input is empty.
static interface	PruneEmptyRules.MinusEmptyPruneRuleConfig	Configuration for a rule that prunes empty inputs from a Minus.
protected static class	PruneEmptyRules.PruneEmptyRule	Abstract prune empty rule that implements SubstitutionRule interface.
static class	PruneEmptyRules.RemoveEmptySingleRule	Rule that converts a relation into empty.
static interface	PruneEmptyRules.SortFetchZeroRuleConfig	Configuration for a rule that prunes a Sort if it has limit 0.
static interface	PruneEmptyRules.UnionEmptyPruneRuleConfig	Configuration for a rule that prunes empty inputs from a Minus.
static interface	PruneEmptyRules.ZeroMaxRowsRuleConfig	Configuration for rule that transforms an empty relational expression into an empty values.

Field Summary

Fields

Modifier and Type	Field	Description
static final RelOptRule	AGGREGATE_INSTANCE	Rule that converts an Aggregate to empty if its child is empty.
static final RelOptRule	CORRELATE_LEFT_INSTANCE	Rule that converts a Correlate to empty if its left child is empty.
static final RelOptRule	CORRELATE_RIGHT_INSTANCE	Rule that converts a Correlate to empty if its right child is empty.
static final RelOptRule	EMPTY_TABLE_INSTANCE	Rule that converts a TableScan to empty if the table has no rows in it.
static final RelOptRule	FILTER_INSTANCE	Rule that converts a Filter to empty if its child is empty.
static final RelOptRule	INTERSECT_INSTANCE	Rule that converts a Intersect to empty if any of its children are empty.
static final RelOptRule	JOIN_LEFT_INSTANCE	Rule that converts a Join to empty if its left child is empty.
static final RelOptRule	JOIN_RIGHT_INSTANCE	Rule that converts a Join to empty if its right child is empty.
static final RelOptRule	MINUS_INSTANCE	Rule that removes empty children of a Minus.
static final RelOptRule	PROJECT_INSTANCE	Rule that converts a Project to empty if its child is empty.
static final RelOptRule	SORT_FETCH_ZERO_INSTANCE	Rule that converts a Sort to empty if it has LIMIT 0.
static final RelOptRule	SORT_INSTANCE	Rule that converts a Sort to empty if its child is empty.
static final RelOptRule	UNION_INSTANCE	Rule that removes empty children of a Union.

Constructor Summary

Constructors

Constructor	Description
PruneEmptyRules()

Method Summary

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Field Details

UNION_INSTANCE

public static final RelOptRule UNION_INSTANCE

Rule that removes empty children of a Union.

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 Minus.

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 Intersect to empty if any of its children are empty.

Examples:

• Intersect(Rel, Empty, Rel2) becomes Empty
• Intersect(Empty, Rel) becomes Empty

EMPTY_TABLE_INSTANCE

public static final RelOptRule EMPTY_TABLE_INSTANCE

Rule that converts a TableScan to empty if the table has no rows in it.

The rule exploits the RelMdMaxRowCount to derive if the table is empty or not.

PROJECT_INSTANCE

public static final RelOptRule PROJECT_INSTANCE

Rule that converts a Project to empty if its child is empty.

Examples:

• Project(Empty) becomes Empty

FILTER_INSTANCE

public static final RelOptRule FILTER_INSTANCE

Rule that converts a Filter 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[fetch=0] 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(Empty, Scan(Dept), LEFT) becomes Empty
• Join(Empty, Scan(Dept), SEMI) becomes Empty
• Join(Empty, Scan(Dept), ANTI) 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
• Join(Scan(Emp), Empty, RIGHT) becomes Empty
• Join(Scan(Emp), Empty, SEMI) becomes Empty
• Join(Scan(Emp), Empty, ANTI) becomes Scan(Emp)

CORRELATE_RIGHT_INSTANCE

public static final RelOptRule CORRELATE_RIGHT_INSTANCE

Rule that converts a Correlate to empty if its right child is empty.

Examples:

• Correlate(Scan(Emp), Empty, INNER) becomes Empty
• Correlate(Scan(Emp), Empty, SEMI) becomes Empty
• Correlate(Scan(Emp), Empty, ANTI) becomes Scan(Emp)
• Correlate(Scan(Emp), Empty, LEFT) becomes Project(Scan(Emp)) where the Project adds additional typed null columns to match the join type output.

CORRELATE_LEFT_INSTANCE

public static final RelOptRule CORRELATE_LEFT_INSTANCE

Rule that converts a Correlate to empty if its left child is empty.

Constructor Details

PruneEmptyRules

public PruneEmptyRules()