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

Interface RelationalExpression.CombineFunction<R,S>

Type Parameters:

R - type of the match result computed while matching quantifiers

S - type of combined match result

Enclosing interface:

RelationalExpression

Functional Interface:

This is a functional interface and can therefore be used as the assignment target for a lambda expression or method reference.

@FunctionalInterface
public static interface RelationalExpression.CombineFunction<R,S>

A functional interface to combine the matches computed over pairs of quantifiers during matching into a result (for the bound correlatedTo set handed into combine(com.apple.foundationdb.record.query.plan.temp.AliasMap, java.lang.Iterable<com.apple.foundationdb.record.query.plan.temp.matching.BoundMatch<com.apple.foundationdb.record.query.plan.temp.EnumeratingIterable<R>>>)). Let's assume we have multiple bindings during matching on the deep correlations (.getCorrelatedTo() of this). Let's call that the sets of outer bindings. We also attempt to match the quantifiers owned by this to the quantifiers of other. For each set of outer bindings we enumerate bindings among the owned quantifiers of the respective expressions. Let's call those sets the inner bindings. For each set out outer bindings there are many sets of inner bindings. At the end of matching we want to establish a match between this expression and some other expression and the quantifiers owned by the respective expressions and their bindings among each other do not matter anymore in terms of matching logic. Those bindings only matter for the result of the match under a set of outer bindings. The matching algorithm returns an iterable of some type S which is computed by a lambda passed in by the caller. It is up to the caller what to do with the outer and inner bindings and how to compute a useful result out of it. The signature of that lambda is defined by this interface. During matching the matching logic calls combine(com.apple.foundationdb.record.query.plan.temp.AliasMap, java.lang.Iterable<com.apple.foundationdb.record.query.plan.temp.matching.BoundMatch<com.apple.foundationdb.record.query.plan.temp.EnumeratingIterable<R>>>) for each set of outer bindings with and Iterable over sets of inner bindings (and their match results).

Method Summary

Modifier and Type	Method	Description
Iterable<S>	combine(AliasMap boundCorrelatedToMap, Iterable<BoundMatch<EnumeratingIterable<R>>> boundMatches)	Combine the sets of bindings (and their results) under the given set of outer bindings to an iterable of combined results.

Method Detail

combine

@Nonnull
Iterable<S> combine(@Nonnull
                    AliasMap boundCorrelatedToMap,
                    @Nonnull
                    Iterable<BoundMatch<EnumeratingIterable<R>>> boundMatches)

Combine the sets of bindings (and their results) under the given set of outer bindings to an iterable of combined results.

Parameters:

boundCorrelatedToMap - set of outer bindings encoded in an AliasMap

boundMatches - iterable of BoundMatches

Returns:

an iterable of type S