Module com.darkcollective.relix.ast

Package com.darkcollective.relix.ast

Record Class TopKNode

java.lang.Object

java.lang.Record

com.darkcollective.relix.ast.TopKNode

Record Components:

groupingAttributes - the partition keys; empty means one global group

sortSpecs - within-group ordering; at least one required

offset - rows to skip within each group before taking count

count - number of rows to keep per group; non-negative

input - the source relation; never null

location - the source location of this node; never null

All Implemented Interfaces:

RelNode

public record TopKNode(List<String> groupingAttributes, List<SortSpecification> sortSpecs, Optional<Long> offset, long count, RelNode input, SourceLocation location)
extends Record
implements RelNode

Top-k per group (TOP) — partitions input by groupingAttributes and, within each group, keeps the count highest rows by sortSpecs (after skipping offset rows).

This is the "N highest rows per group" operation — top 3 orders by amount per customer — that SQL forces into a ROW_NUMBER() OVER (PARTITION BY … ORDER BY …) ≤ k plus an outer filter, or a lateral join. Unlike a global LimitNode it cannot push down and buffers each group; unlike an AggregationNode it returns whole rows.

The output schema is the input schema (it is a windowed filter — a row subset). At least one sort specification is required.

The surface syntax always names a partition key (TOP … PER …), but the grouping list may be empty: that is the global top-N — one group containing every row — which the optimizer produces by fusing a λ over a τ (LIM-003). It has no spelling of its own because λ/τ already is one.

Example: TOP 3 amount DESC PER customer_id (Orders).

Constructor Summary

Constructors

Constructor	Description
TopKNode(List<String> groupingAttributes, List<SortSpecification> sortSpecs, long count, RelNode input)	Convenience constructor for tests; no offset, SourceLocation.UNKNOWN.
TopKNode(List<String> groupingAttributes, List<SortSpecification> sortSpecs, Optional<Long> offset, long count, RelNode input, SourceLocation location)	Creates an instance of a TopKNode record class.

Method Summary

Modifier and Type	Method	Description
<R> R	accept(RelNodeVisitor<R> visitor)
long	count()	Returns the value of the count record component.
final boolean	equals(Object o)	Indicates whether some other object is "equal to" this one.
List<String>	groupingAttributes()	Returns the value of the groupingAttributes record component.
final int	hashCode()	Returns a hash code value for this object.
RelNode	input()	Returns the value of the input record component.
SourceLocation	location()	Returns the value of the location record component.
Optional<Long>	offset()	Returns the value of the offset record component.
List<SortSpecification>	sortSpecs()	Returns the value of the sortSpecs record component.
final String	toString()	Returns a string representation of this record class.

Methods inherited from class java.lang.Object

clone, finalize, getClass, notify, notifyAll, wait, wait, wait

Methods inherited from interface com.darkcollective.relix.ast.RelNode

children, mapChildren, materializationMode, prettyPrint

Constructor Details

TopKNode

public TopKNode(List<String> groupingAttributes,
 List<SortSpecification> sortSpecs,
 Optional<Long> offset,
 long count,
 RelNode input,
 SourceLocation location)

Creates an instance of a TopKNode record class.

Parameters:

groupingAttributes - the value for the groupingAttributes record component

sortSpecs - the value for the sortSpecs record component

offset - the value for the offset record component

count - the value for the count record component

input - the value for the input record component

location - the value for the location record component

TopKNode

public TopKNode(List<String> groupingAttributes,
 List<SortSpecification> sortSpecs,
 long count,
 RelNode input)

Convenience constructor for tests; no offset, SourceLocation.UNKNOWN.

Method Details

accept

public <R> R accept(RelNodeVisitor<R> visitor)

Specified by:

accept in interface RelNode

toString

public final String toString()

Returns a string representation of this record class. The representation contains the name of the class, followed by the name and value of each of the record components.

Specified by:

toString in class Record

Returns:

a string representation of this object

hashCode

public final int hashCode()

Returns a hash code value for this object. The value is derived from the hash code of each of the record components.

Specified by:

hashCode in class Record

Returns:

a hash code value for this object

equals

public final boolean equals(Object o)

Indicates whether some other object is "equal to" this one. The objects are equal if the other object is of the same class and if all the record components are equal. Reference components are compared with Objects::equals(Object,Object); primitive components are compared with '=='.

Specified by:

equals in class Record

Parameters:

o - the object with which to compare

Returns:

true if this object is the same as the o argument; false otherwise.

groupingAttributes

public List<String> groupingAttributes()

Returns the value of the groupingAttributes record component.

Returns:

the value of the groupingAttributes record component

sortSpecs

public List<SortSpecification> sortSpecs()

Returns the value of the sortSpecs record component.

Returns:

the value of the sortSpecs record component

offset

public Optional<Long> offset()

Returns the value of the offset record component.

Returns:

the value of the offset record component

count

public long count()

Returns the value of the count record component.

Returns:

the value of the count record component

input

public RelNode input()

Returns the value of the input record component.

Returns:

the value of the input record component

location

public SourceLocation location()

Returns the value of the location record component.

Specified by:

location in interface RelNode

Returns:

the value of the location record component