Package io.trino.operator.window.pattern

Class SetEvaluator

java.lang.Object

io.trino.operator.window.pattern.SetEvaluator

public class SetEvaluator
extends Object

This class returns a set of positions to aggregate over for an aggregate function in row pattern matching context. Aggregations in row pattern matching context have RUNNING or FINAL semantics, and they apply only to rows matched with certain pattern variables. For example, for a match "A B A A B", the aggregation `sum(B.x)` only applies to the second and the last position.

This evaluator is stateful. It requires a reset for every new match. The method `resolveNewPositions()` returns a portion of positions corresponding to the new portion of the match since the last call. It is thus assumed that a sequence of calls since the instance creation or `reset()` applies to the same match (i.e. the `matchedLabels` passed as an argument to one call is prefix of `matchedLabels` passed in the next call).

Also, a full list of positions for a current match is kept, and it can be obtained via the `getAllPositions()` method. This is for the purpose comparing pattern matching threads in ThreadEquivalence.

Nested Class Summary

Nested Classes

Modifier and Type	Class	Description
static class	SetEvaluator.SetEvaluatorSupplier

Constructor Summary

Constructors

Constructor	Description
SetEvaluator(Set<Integer> labels, boolean running)

Method Summary

Modifier and Type	Method	Description
SetEvaluator	copy()
ArrayView	getAllPositions(ArrayView labels)
long	getAllPositionsSizeInBytes()
void	reset()
ArrayView	resolveNewPositions(int currentRow, ArrayView matchedLabels, int partitionStart, int patternStart)	This method is used for resolving positions for aggregation: - During pattern matching.

Methods inherited from class java.lang.Object

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

Constructor Details

SetEvaluator

public SetEvaluator(Set<Integer> labels,
 boolean running)

Method Details

reset

public void reset()

resolveNewPositions

public ArrayView resolveNewPositions(int currentRow,
 ArrayView matchedLabels,
 int partitionStart,
 int patternStart)

This method is used for resolving positions for aggregation: - During pattern matching. In this case, the evaluated label has been appended to `matchedLabels` - When computing row pattern measures after a non-empty match is found. Search is limited up to the current row in case of RUNNING semantics and to the entire match in case of FINAL semantics.

TODO If `evaluated` exceeds `aggregated`, we could reuse the pre-evaluated positions. For that, we need to keep count of all previously returned positions from the `aggregated` prefix.

Returns:

array of new matching positions since the last call, relative to partition start

getAllPositions

public ArrayView getAllPositions(ArrayView labels)

copy

public SetEvaluator copy()

getAllPositionsSizeInBytes

public long getAllPositionsSizeInBytes()