Examples with TopNSequence org.apache.druid.java.util.common.guava.TopNSequence used on opensource projects

Example 1 with TopNSequence

use of org.apache.druid.java.util.common.guava.TopNSequence in project druid by druid-io.

the class DefaultLimitSpec method build.

@Override
public Function<Sequence<ResultRow>, Sequence<ResultRow>> build(final GroupByQuery query) {
    final List<DimensionSpec> dimensions = query.getDimensions();
    // Can avoid re-sorting if the natural ordering is good enough.
    boolean sortingNeeded = dimensions.size() < columns.size();
    final Set<String> aggAndPostAggNames = new HashSet<>();
    for (AggregatorFactory agg : query.getAggregatorSpecs()) {
        aggAndPostAggNames.add(agg.getName());
    }
    for (PostAggregator postAgg : query.getPostAggregatorSpecs()) {
        aggAndPostAggNames.add(postAgg.getName());
    }
    if (!sortingNeeded) {
        for (int i = 0; i < columns.size(); i++) {
            final OrderByColumnSpec columnSpec = columns.get(i);
            if (aggAndPostAggNames.contains(columnSpec.getDimension())) {
                sortingNeeded = true;
                break;
            }
            final ColumnType columnType = getOrderByType(columnSpec, dimensions);
            final StringComparator naturalComparator;
            if (columnType.is(ValueType.STRING)) {
                naturalComparator = StringComparators.LEXICOGRAPHIC;
            } else if (columnType.isNumeric()) {
                naturalComparator = StringComparators.NUMERIC;
            } else if (columnType.isArray()) {
                if (columnType.getElementType().isNumeric()) {
                    naturalComparator = StringComparators.NUMERIC;
                } else {
                    naturalComparator = StringComparators.LEXICOGRAPHIC;
                }
            } else {
                sortingNeeded = true;
                break;
            }
            if (columnSpec.getDirection() != OrderByColumnSpec.Direction.ASCENDING || !columnSpec.getDimensionComparator().equals(naturalComparator) || !columnSpec.getDimension().equals(dimensions.get(i).getOutputName())) {
                sortingNeeded = true;
                break;
            }
        }
    }
    if (!sortingNeeded) {
        // If granularity is ALL, sortByDimsFirst doesn't change the sorting order.
        sortingNeeded = !query.getGranularity().equals(Granularities.ALL) && query.getContextSortByDimsFirst();
    }
    if (!sortingNeeded) {
        String timestampField = query.getContextValue(GroupByQuery.CTX_TIMESTAMP_RESULT_FIELD);
        if (timestampField != null && !timestampField.isEmpty()) {
            int timestampResultFieldIndex = query.getContextValue(GroupByQuery.CTX_TIMESTAMP_RESULT_FIELD_INDEX);
            sortingNeeded = query.getContextSortByDimsFirst() ? timestampResultFieldIndex != query.getDimensions().size() - 1 : timestampResultFieldIndex != 0;
        }
    }
    final Function<Sequence<ResultRow>, Sequence<ResultRow>> sortAndLimitFn;
    if (sortingNeeded) {
        // Materialize the Comparator first for fast-fail error checking.
        final Ordering<ResultRow> ordering = makeComparator(query.getResultRowSignature(), query.getResultRowHasTimestamp(), query.getDimensions(), query.getAggregatorSpecs(), query.getPostAggregatorSpecs(), query.getContextSortByDimsFirst());
        // underlying data isn't changing. (Useful for query reproducibility and offset-based pagination.)
        if (isLimited()) {
            sortAndLimitFn = results -> new TopNSequence<>(results, ordering, limit + offset);
        } else {
            sortAndLimitFn = results -> Sequences.sort(results, ordering).limit(limit + offset);
        }
    } else {
        if (isLimited()) {
            sortAndLimitFn = results -> results.limit(limit + offset);
        } else {
            sortAndLimitFn = Functions.identity();
        }
    }
    // Finally, apply offset after sorting and limiting.
    if (isOffset()) {
        return results -> sortAndLimitFn.apply(results).skip(offset);
    } else {
        return sortAndLimitFn;
    }
}