Package com.apple.foundationdb.record.query.plan.temp.matchers

Class ListChildrenMatcher

java.lang.Object

com.apple.foundationdb.record.query.plan.temp.matchers.ListChildrenMatcher

All Implemented Interfaces:

ExpressionChildrenMatcher

public class ListChildrenMatcher
extends Object
implements ExpressionChildrenMatcher

A matcher for a children that tries to match each child to a specified matcher. It implements the "default" matching for children, as exposed by the TypeMatcher.of(Class, ExpressionMatcher[]) helper method.

If every child matches the specified matcher and if every matcher matches a child, the ListChildrenMatcher returns a stream of bindings that includes the Cartesian product of the stream of bindings from each child. Note that this matcher can only match a fixed number of children. Currently, matching is not especially efficient: the cross product is computed by collecting each child stream into a list.

Method Summary

Modifier and Type	Method	Description
static ListChildrenMatcher	empty()	Get a matcher with no child matchers which matches an empty collection of children.
Stream<PlannerBindings>	matches(PlannerBindings outerBindings, List<? extends Bindable> children)	Apply this matcher to the children provided by the given iterator and produce a stream of possible bindings.
static ListChildrenMatcher	of(List<ExpressionMatcher<? extends Bindable>> childMatchers)	Get a matcher that tries to match the planner expression children, in order, to the given list of ExpressionMatchers.

Methods inherited from class java.lang.Object

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

Method Detail

matches

@Nonnull
public Stream<PlannerBindings> matches(@Nonnull
                                       PlannerBindings outerBindings,
                                       @Nonnull
                                       List<? extends Bindable> children)

Description copied from interface: ExpressionChildrenMatcher

Apply this matcher to the children provided by the given iterator and produce a stream of possible bindings. If the match is not successful, produce an empty stream. Note that this method should not generally match to the children themselves; instead, it should delegate that work to one or more inner ExpressionMatchers.

Specified by:

matches in interface ExpressionChildrenMatcher

Parameters:

outerBindings - preexisting bindings supplied by the caller

children - a list of references to the children of a planner expression

Returns:

a stream of the possible bindings from applying this match to the children in the given iterator

empty

@Nonnull
public static ListChildrenMatcher empty()

Get a matcher with no child matchers which matches an empty collection of children. The returned matcher may be a static instance and may not be distinct across different calls. Unlike an ExpressionMatcher, an ExpressionChildrenMatcher is not used for creating bindings and so need not be a distinct object.

Returns:

a matcher that matches an empty collection of children

of

@Nonnull
public static ListChildrenMatcher of(List<ExpressionMatcher<? extends Bindable>> childMatchers)

Get a matcher that tries to match the planner expression children, in order, to the given list of ExpressionMatchers.

Parameters:

childMatchers - a list of matcher for the children, in order

Returns:

a matcher that attempts to match the children, in order, to the given list of matchers