vvysotskyi commented on a change in pull request #1810: DRILL-7271: Refactor Metadata interfaces and classes to contain all needed information for the File based Metastore URL: https://github.com/apache/drill/pull/1810#discussion_r296248847
########## File path: metastore/metastore-api/src/main/java/org/apache/drill/metastore/TableMetadataUtils.java ########## @@ -0,0 +1,135 @@ +/* + * Licensed to the Apache Software Foundation (ASF) under one + * or more contributor license agreements. See the NOTICE file + * distributed with this work for additional information + * regarding copyright ownership. The ASF licenses this file + * to you under the Apache License, Version 2.0 (the + * "License"); you may not use this file except in compliance + * with the License. You may obtain a copy of the License at + * + * http://www.apache.org/licenses/LICENSE-2.0 + * + * Unless required by applicable law or agreed to in writing, software + * distributed under the License is distributed on an "AS IS" BASIS, + * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. + * See the License for the specific language governing permissions and + * limitations under the License. + */ +package org.apache.drill.metastore; + +import org.apache.drill.common.expression.SchemaPath; +import org.apache.drill.common.types.TypeProtos; +import org.apache.drill.metastore.metadata.BaseMetadata; +import org.apache.drill.metastore.metadata.TableMetadata; +import org.apache.drill.metastore.statistics.CollectableColumnStatisticsKind; +import org.apache.drill.metastore.statistics.ColumnStatistics; +import org.apache.drill.metastore.statistics.ColumnStatisticsKind; +import org.apache.drill.metastore.statistics.StatisticsHolder; +import org.apache.drill.metastore.statistics.TableStatisticsKind; +import org.apache.drill.shaded.guava.com.google.common.primitives.UnsignedBytes; + +import java.util.ArrayList; +import java.util.Collection; +import java.util.Collections; +import java.util.Comparator; +import java.util.HashMap; +import java.util.List; +import java.util.Map; +import java.util.Set; + +public class TableMetadataUtils { + + private TableMetadataUtils() { + throw new IllegalStateException("Utility class"); + } + + /** + * Returns {@link Comparator} instance considering specified {@code type}. + * + * @param type type of the column + * @return {@link Comparator} instance + */ + public static Comparator getComparator(TypeProtos.MinorType type) { + switch (type) { + case INTERVALDAY: + case INTERVAL: + case INTERVALYEAR: + return Comparator.nullsFirst(UnsignedBytes.lexicographicalComparator()); + case UINT1: + return Comparator.nullsFirst(UnsignedBytes::compare); + case UINT2: + case UINT4: + return Comparator.nullsFirst(Integer::compareUnsigned); + case UINT8: + return Comparator.nullsFirst(Long::compareUnsigned); + default: + return getNaturalNullsFirstComparator(); + } + } + + /** + * Returns "natural order" comparator which threads nulls as min values. + * + * @param <T> type to compare + * @return "natural order" comparator + */ + public static <T extends Comparable<T>> Comparator<T> getNaturalNullsFirstComparator() { + return Comparator.nullsFirst(Comparator.naturalOrder()); + } + + /** + * Merges list of specified metadata into the map of {@link ColumnStatistics} with columns as keys. + * + * @param <T> type of metadata to collect + * @param metadataList list of metadata to be merged + * @param columns set of columns whose statistics should be merged + * @param statisticsToCollect kinds of statistics that should be collected + * @return list of merged metadata + */ + public static <T extends BaseMetadata> Map<SchemaPath, ColumnStatistics> mergeColumnsStatistics( + Collection<T> metadataList, Set<SchemaPath> columns, List<CollectableColumnStatisticsKind> statisticsToCollect) { + Map<SchemaPath, ColumnStatistics> columnsStatistics = new HashMap<>(); + + for (SchemaPath column : columns) { + List<ColumnStatistics> statisticsList = new ArrayList<>(); + for (T metadata : metadataList) { + ColumnStatistics statistics = metadata.getColumnsStatistics().get(column); + if (statistics == null) { + // schema change happened, set statistics which represents all nulls + statistics = new ColumnStatistics( + Collections.singletonList( + new StatisticsHolder<>(TableStatisticsKind.ROW_COUNT.getValue(metadata), ColumnStatisticsKind.NULLS_COUNT))); + } + statisticsList.add(statistics); + } + List<StatisticsHolder> statisticsHolders = new ArrayList<>(); + for (CollectableColumnStatisticsKind statisticsKind : statisticsToCollect) { + Object mergedStatistic = statisticsKind.mergeStatistics(statisticsList); + statisticsHolders.add(new StatisticsHolder<>(mergedStatistic, statisticsKind)); + } + columnsStatistics.put(column, new ColumnStatistics<>(statisticsHolders, statisticsList.iterator().next().getComparatorType())); Review comment: Thanks for pointing this, added check for this case. ---------------------------------------------------------------- This is an automated message from the Apache Git Service. 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