rdblue commented on code in PR #14533: URL: https://github.com/apache/iceberg/pull/14533#discussion_r2540011792
########## core/src/main/java/org/apache/iceberg/V4ManifestReader.java: ########## @@ -0,0 +1,219 @@ +/* + * 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.io.ByteArrayInputStream; +import java.io.DataInputStream; +import java.io.IOException; +import java.nio.ByteBuffer; +import java.util.Collection; +import java.util.List; +import java.util.function.Function; +import org.apache.iceberg.exceptions.RuntimeIOException; +import org.apache.iceberg.io.CloseableGroup; +import org.apache.iceberg.io.CloseableIterable; +import org.apache.iceberg.io.CloseableIterator; +import org.apache.iceberg.io.InputFile; +import org.apache.iceberg.relocated.com.google.common.base.Preconditions; +import org.apache.iceberg.relocated.com.google.common.collect.ImmutableList; +import org.apache.iceberg.relocated.com.google.common.collect.Lists; +import org.apache.iceberg.types.Types; +import org.roaringbitmap.RoaringBitmap; + +/** + * Reader for V4 manifest files containing TrackedFile entries. + * + * <p>Supports reading both root manifests and leaf manifests. Returns TrackedFile entries which can + * represent data files, delete files, or manifest references. TODO: implement caching. + */ +class V4ManifestReader extends CloseableGroup implements CloseableIterable<TrackedFile<?>> { + static final ImmutableList<String> ALL_COLUMNS = ImmutableList.of("*"); Review Comment: The original `ManifestReader` allows callers to project columns by calling `select(String... columns)`, but this isn't a very useful API because the majority of the time that a manifest is being projected, it is by the Iceberg library for a specific purpose. That's why the arguments to `select` are usually `"*"`, `BaseScan.SCAN_WITH_STATS_COLUMNS`, or `BaseScan.SCAN_COLUMNS`. And now that we need to project columnar stats based on fields used in filters, the last two constants are no longer useful. I think that the v4 implementation should provide more useful projection capabilities: 1. By default, all columns are projected, but without needing to check for `*` 2. A filter-based stats projection that is automatic, based on the filters pushed down to this reader 3. A custom stats projection like `projectStats(Set<Integer> fieldIds)` that sets the content stats projection (to be unioned with the fields from #2) 4. A `project(Schema)` method that can perform more fine-grained projection when the reader is used in metadata table scans and other custom scan situations (like `ManifestFiles.readPaths`). Removing `select` from the API allows us to simplify the logic in this reader. We don't need to keep lists of fields to pass in or detect when both `select` and `project` are called. -- 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]
