[GitHub] [iceberg] rdblue commented on a change in pull request #1858: Core: Add SortedPosDeleteWriter

[GitBox <gi...@apache.org>]

rdblue commented on a change in pull request #1858:
URL: https://github.com/apache/iceberg/pull/1858#discussion_r536918599



##########
File path: core/src/main/java/org/apache/iceberg/io/SortedPosDeleteWriter.java
##########
@@ -0,0 +1,172 @@
+/*
+ * 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.io;
+
+import java.io.Closeable;
+import java.io.IOException;
+import java.io.UncheckedIOException;
+import java.util.Comparator;
+import java.util.List;
+import java.util.Set;
+import org.apache.iceberg.DeleteFile;
+import org.apache.iceberg.FileFormat;
+import org.apache.iceberg.PartitionKey;
+import org.apache.iceberg.deletes.PositionDeleteWriter;
+import org.apache.iceberg.encryption.EncryptedOutputFile;
+import org.apache.iceberg.relocated.com.google.common.collect.Lists;
+import org.apache.iceberg.relocated.com.google.common.collect.Maps;
+import org.apache.iceberg.relocated.com.google.common.collect.Multimap;
+import org.apache.iceberg.relocated.com.google.common.collect.Multimaps;
+import org.apache.iceberg.types.Comparators;
+import org.apache.iceberg.util.CharSequenceSet;
+import org.apache.iceberg.util.CharSequenceWrapper;
+
+class SortedPosDeleteWriter<T> implements Closeable {
+  private static final long DEFAULT_RECORDS_NUM_THRESHOLD = 100_000L;
+
+  private final Multimap<CharSequenceWrapper, PosValue<T>> posDeletes =
+      Multimaps.newMultimap(Maps.newHashMap(), Lists::newArrayList);
+  private final List<DeleteFile> completedFiles = Lists.newArrayList();
+  private final Set<CharSequence> referencedDataFiles = CharSequenceSet.empty();
+  private final CharSequenceWrapper wrapper = CharSequenceWrapper.wrap(null);
+
+  private final FileAppenderFactory<T> appenderFactory;
+  private final OutputFileFactory fileFactory;
+  private final FileFormat format;
+  private final PartitionKey partition;
+  private final long recordsNumThreshold;
+
+  private int records = 0;
+
+  SortedPosDeleteWriter(FileAppenderFactory<T> appenderFactory,
+                        OutputFileFactory fileFactory,
+                        FileFormat format,
+                        PartitionKey partition,
+                        long recordsNumThreshold) {
+    this.appenderFactory = appenderFactory;
+    this.fileFactory = fileFactory;
+    this.format = format;
+    this.partition = partition;
+    this.recordsNumThreshold = recordsNumThreshold;
+  }
+
+  SortedPosDeleteWriter(FileAppenderFactory<T> appenderFactory,
+                        OutputFileFactory fileFactory,
+                        FileFormat format,
+                        PartitionKey partition) {
+    this(appenderFactory, fileFactory, format, partition, DEFAULT_RECORDS_NUM_THRESHOLD);
+  }
+
+  public void delete(CharSequence path, long pos) {
+    delete(path, pos, null);
+  }
+
+  public void delete(CharSequence path, long pos, T row) {
+    posDeletes.put(CharSequenceWrapper.wrap(path), PosValue.of(pos, row));

Review comment:
       Using a multimap requires this to create a new `CharSequenceWrapper` for each delete, even though we expect a very small set of keys. I think it would be better to use a regular map so that a new wrapper is created for only the first delete in each file:
   
   ```java
     List<PosValue<T>> values = posDeletes.get(wrapper.set(path));
     if (values != null) {
       values.add(PosValue.of(pos, row));
     } else {
       posDeletes.add(Lists.newArrayList(PosValue.of(pos, row)));
     }
     ...
   ```




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