Examples with EnumeratingIterable com.apple.foundationdb.record.query.combinatorics.EnumeratingIterable used on opensource projects

Example 1 with EnumeratingIterable

use of com.apple.foundationdb.record.query.combinatorics.EnumeratingIterable in project fdb-record-layer by FoundationDB.

the class SelectExpression method subsumedBy.

@Nonnull
@Override
public Iterable<MatchInfo> subsumedBy(@Nonnull final RelationalExpression candidateExpression, @Nonnull final AliasMap aliasMap, @Nonnull final IdentityBiMap<Quantifier, PartialMatch> partialMatchMap) {
    // TODO This method should be simplified by adding some structure to it.
    final Collection<MatchInfo> matchInfos = PartialMatch.matchesFromMap(partialMatchMap);
    Verify.verify(this != candidateExpression);
    if (getClass() != candidateExpression.getClass()) {
        return ImmutableList.of();
    }
    final SelectExpression otherSelectExpression = (SelectExpression) candidateExpression;
    // merge parameter maps -- early out if a binding clashes
    final ImmutableList<Map<CorrelationIdentifier, ComparisonRange>> parameterBindingMaps = matchInfos.stream().map(MatchInfo::getParameterBindingMap).collect(ImmutableList.toImmutableList());
    final Optional<Map<CorrelationIdentifier, ComparisonRange>> mergedParameterBindingMapOptional = MatchInfo.tryMergeParameterBindings(parameterBindingMaps);
    if (!mergedParameterBindingMapOptional.isPresent()) {
        return ImmutableList.of();
    }
    final Map<CorrelationIdentifier, ComparisonRange> mergedParameterBindingMap = mergedParameterBindingMapOptional.get();
    final ImmutableSet.Builder<CorrelationIdentifier> matchedCorrelatedToBuilder = ImmutableSet.builder();
    // for-each quantifiers. Also keep track of all aliases the matched quantifiers are correlated to.
    for (final Quantifier quantifier : getQuantifiers()) {
        if (partialMatchMap.containsKeyUnwrapped(quantifier)) {
            if (quantifier instanceof Quantifier.ForEach) {
                // current quantifier is matched
                final PartialMatch childPartialMatch = Objects.requireNonNull(partialMatchMap.getUnwrapped(quantifier));
                if (!childPartialMatch.getQueryExpression().computeUnmatchedForEachQuantifiers(childPartialMatch).isEmpty()) {
                    return ImmutableList.of();
                }
            }
            matchedCorrelatedToBuilder.addAll(quantifier.getCorrelatedTo());
        }
    }
    for (final Value resultValue : getResultValues()) {
        matchedCorrelatedToBuilder.addAll(resultValue.getCorrelatedTo());
    }
    final ImmutableSet<CorrelationIdentifier> matchedCorrelatedTo = matchedCorrelatedToBuilder.build();
    if (getQuantifiers().stream().anyMatch(quantifier -> quantifier instanceof Quantifier.ForEach && !partialMatchMap.containsKeyUnwrapped(quantifier))) {
        return ImmutableList.of();
    }
    final boolean allNonMatchedQuantifiersIndependent = getQuantifiers().stream().filter(quantifier -> !partialMatchMap.containsKeyUnwrapped(quantifier)).noneMatch(quantifier -> matchedCorrelatedTo.contains(quantifier.getAlias()));
    if (!allNonMatchedQuantifiersIndependent) {
        return ImmutableList.of();
    }
    // Loop through all for each quantifiers on the other side to ensure that they are all matched.
    // If any are not matched we cannot establish a match at all.
    final boolean allOtherForEachQuantifiersMatched = otherSelectExpression.getQuantifiers().stream().filter(quantifier -> quantifier instanceof Quantifier.ForEach).allMatch(quantifier -> aliasMap.containsTarget(quantifier.getAlias()));
    // would help us here to make sure the additional non-matched quantifier is not eliminating records.
    if (!allOtherForEachQuantifiersMatched) {
        return ImmutableList.of();
    }
    // 
    // Map predicates on the query side to predicates on the candidate side. Record parameter bindings and/or
    // compensations for each mapped predicate.
    // A predicate on this side (the query side) can cause us to filter out rows, a mapped predicate (for that
    // predicate) can only filter out fewer rows which is correct and can be compensated for. The important part
    // is that we must not have predicates on the other (candidate) side at the end of this mapping process which
    // would mean that the candidate eliminates records that the query side may not eliminate. If we detect that
    // case we MUST not create a match.
    // 
    final ImmutableList.Builder<Iterable<PredicateMapping>> predicateMappingsBuilder = ImmutableList.builder();
    // 
    if (getPredicates().isEmpty()) {
        final boolean allNonFiltering = otherSelectExpression.getPredicates().stream().allMatch(queryPredicate -> queryPredicate instanceof Placeholder || queryPredicate.isTautology());
        if (allNonFiltering) {
            return MatchInfo.tryMerge(partialMatchMap, mergedParameterBindingMap, PredicateMap.empty()).map(ImmutableList::of).orElse(ImmutableList.of());
        } else {
            return ImmutableList.of();
        }
    }
    for (final QueryPredicate predicate : getPredicates()) {
        final Set<PredicateMapping> impliedMappingsForPredicate = predicate.findImpliedMappings(aliasMap, otherSelectExpression.getPredicates());
        predicateMappingsBuilder.add(impliedMappingsForPredicate);
    }
    // 
    // We now have a multimap from predicates on the query side to predicates on the candidate side. In the trivial
    // case this multimap only contains singular mappings for a query predicate. If it doesn't we need to enumerate
    // through their cross product exhaustively. Each complete and non-contradictory element of that cross product
    // can lead to a match.
    // 
    final EnumeratingIterable<PredicateMapping> crossedMappings = CrossProduct.crossProduct(predicateMappingsBuilder.build());
    return IterableHelpers.flatMap(crossedMappings, predicateMappings -> {
        final Set<QueryPredicate> unmappedOtherPredicates = Sets.newIdentityHashSet();
        unmappedOtherPredicates.addAll(otherSelectExpression.getPredicates());
        final Map<CorrelationIdentifier, ComparisonRange> parameterBindingMap = Maps.newHashMap();
        final PredicateMap.Builder predicateMapBuilder = PredicateMap.builder();
        for (final PredicateMapping predicateMapping : predicateMappings) {
            predicateMapBuilder.put(predicateMapping.getQueryPredicate(), predicateMapping);
            unmappedOtherPredicates.remove(predicateMapping.getCandidatePredicate());
            final Optional<CorrelationIdentifier> parameterAliasOptional = predicateMapping.getParameterAliasOptional();
            final Optional<ComparisonRange> comparisonRangeOptional = predicateMapping.getComparisonRangeOptional();
            if (parameterAliasOptional.isPresent() && comparisonRangeOptional.isPresent()) {
                parameterBindingMap.put(parameterAliasOptional.get(), comparisonRangeOptional.get());
            }
        }
        // 
        // Last chance for unmapped predicates - if there is a placeholder or a tautology on the other side that is still
        // unmapped, we can (and should) remove it from the unmapped other set now. The reasoning is that this predicate is
        // not filtering so it does not cause records to be filtered that are not filtered on the query side.
        // 
        unmappedOtherPredicates.removeIf(queryPredicate -> queryPredicate instanceof Placeholder || queryPredicate.isTautology());
        if (!unmappedOtherPredicates.isEmpty()) {
            return ImmutableList.of();
        }
        final Optional<? extends PredicateMap> predicateMapOptional = predicateMapBuilder.buildMaybe();
        return predicateMapOptional.map(predicateMap -> {
            final Optional<Map<CorrelationIdentifier, ComparisonRange>> allParameterBindingMapOptional = MatchInfo.tryMergeParameterBindings(ImmutableList.of(mergedParameterBindingMap, parameterBindingMap));
            return allParameterBindingMapOptional.flatMap(allParameterBindingMap -> MatchInfo.tryMerge(partialMatchMap, allParameterBindingMap, predicateMap)).map(ImmutableList::of).orElse(ImmutableList.of());
        }).orElse(ImmutableList.of());
    });
}