stevenzwu commented on code in PR #17322: URL: https://github.com/apache/iceberg/pull/17322#discussion_r3634542557
########## core/src/main/java/org/apache/iceberg/ContentStatsBackedMap.java: ########## @@ -0,0 +1,164 @@ +/* + * 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.iceberg; + +import java.nio.ByteBuffer; +import java.util.AbstractMap; +import java.util.Map; +import java.util.Set; +import org.apache.iceberg.relocated.com.google.common.collect.Maps; +import org.apache.iceberg.types.Conversions; +import org.apache.iceberg.types.Types; + +/** + * A lazy, read-only {@link Map} view of one stat across the columns of a {@link ContentStats}, + * keyed by field ID, mirroring the per-column stat maps on {@link ContentFile}. + */ +class ContentStatsBackedMap<V> extends AbstractMap<Integer, V> { + enum Kind { + VALUE_COUNT, + NULL_VALUE_COUNT, + NAN_VALUE_COUNT, + LOWER_BOUND, + UPPER_BOUND + } + + private final ContentStats stats; + private final Kind kind; + private Map<Integer, V> materialized; + + ContentStatsBackedMap(ContentStats stats, Kind kind) { + this.stats = stats; + this.kind = kind; + } + + /** Returns a lazy view of the metric across columns, or {@code null} if no column tracks it. */ + static <V> Map<Integer, V> forKind(Kind kind, ContentStats stats) { + return isEmpty(stats, kind) ? null : new ContentStatsBackedMap<>(stats, kind); + } + + @Override + public V get(Object key) { + if (!(key instanceof Integer)) { + throw new ClassCastException("Key must be an Integer field id: " + key); + } + + FieldStats<?> fieldStats = stats.statsFor((Integer) key); + if (fieldStats == null) { + return null; + } + + return getStatValue(fieldStats, kind); + } + + @Override + public boolean containsKey(Object key) { + return get(key) != null; + } + + @Override + public boolean isEmpty() { + // avoid AbstractMap's default, which materializes entrySet() just to answer emptiness + return isEmpty(stats, kind); + } + + @Override + public Set<Entry<Integer, V>> entrySet() { + if (materialized == null) { + Map<Integer, V> entries = Maps.newLinkedHashMap(); + for (FieldStats<?> fieldStats : stats.fieldStats()) { + if (fieldStats != null) { + V value = getStatValue(fieldStats, kind); + if (value != null) { + entries.put(fieldStats.fieldId(), value); + } + } + } + + this.materialized = entries; + } + + return materialized.entrySet(); + } + + /** Returns whether no column contributes an entry for the metric. */ + static boolean isEmpty(ContentStats stats, Kind kind) { + for (FieldStats<?> fieldStats : stats.fieldStats()) { + if (fieldStats != null && contributes(fieldStats, kind)) { + return false; + } + } + + return true; + } + + // Whether getStatValue would return a non-null value, without allocating a boxed count or + // decoding a bound. Must mirror getStatValue's null-ness. + private static boolean contributes(FieldStats<?> fieldStats, Kind kind) { + switch (kind) { + case VALUE_COUNT: + return true; + case NULL_VALUE_COUNT: + return fieldStats.hasNullCount(); + case NAN_VALUE_COUNT: + return fieldStats.hasNaNCount(); + case LOWER_BOUND: + return fieldStats.lowerBound() != null + && tracksStat(fieldStats, StatsUtil.LOWER_BOUND_OFFSET); + case UPPER_BOUND: + return fieldStats.upperBound() != null + && tracksStat(fieldStats, StatsUtil.UPPER_BOUND_OFFSET); + default: + throw new IllegalArgumentException("Unknown content stats kind: " + kind); + } + } + + // Whether the field's stats struct declares the metric at the given offset. + private static boolean tracksStat(FieldStats<?> fieldStats, int statOffset) { + return fieldStats.type().field(StatsUtil.toBaseId(fieldStats.fieldId()) + statOffset) != null; + } + + @SuppressWarnings("unchecked") + private static <V> V getStatValue(FieldStats<?> fieldStats, Kind kind) { + switch (kind) { + case VALUE_COUNT: + return (V) Long.valueOf(fieldStats.valueCount()); + case NULL_VALUE_COUNT: + return fieldStats.hasNullCount() ? (V) Long.valueOf(fieldStats.nullValueCount()) : null; + case NAN_VALUE_COUNT: + return fieldStats.hasNaNCount() ? (V) Long.valueOf(fieldStats.nanValueCount()) : null; + case LOWER_BOUND: + return (V) bound(fieldStats, fieldStats.lowerBound(), StatsUtil.LOWER_BOUND_OFFSET); + case UPPER_BOUND: + return (V) bound(fieldStats, fieldStats.upperBound(), StatsUtil.UPPER_BOUND_OFFSET); + default: + throw new IllegalArgumentException("Unknown content stats kind: " + kind); + } + } + + private static ByteBuffer bound(FieldStats<?> fieldStats, Object bound, int boundOffset) { + Types.NestedField boundField = + fieldStats.type().field(StatsUtil.toBaseId(fieldStats.fieldId()) + boundOffset); + if (bound == null || boundField == null) { Review Comment: > Also, it is easier to look up the bound field by name rather than ID: I also thought about it. it is also probably slightly better to query by name `lower_bound`, as the `FieldStatsStruct` constructor internally already triggered `lazyFieldsByName()` mapping. ``` this.boundType = struct.fieldType("lower_bound"); ``` Earlier, I used `id` because it is the canonical identifier defined in `StatsUtil`, while field names are not exposed constants in `StatsUtil`. I don't want to use hardcoded literals here. But since [field name is also part of the spec](https://iceberg.apache.org/spec/#field-statistics), we can add the stat field name constants to `StatsUtil` just like the stat field offset. Either way, we should be consistent in the wrapper and the `FieldStatsStruct` constructor. -- This is an automated message from the Apache Git Service. To respond to the message, please log on to GitHub and use the URL above to go to the specific comment. To unsubscribe, e-mail: [email protected] For queries about this service, please contact Infrastructure at: [email protected] --------------------------------------------------------------------- To unsubscribe, e-mail: [email protected] For additional commands, e-mail: [email protected]
