[GitHub] [beam] abhiy13 commented on a change in pull request #12490: [BEAM-10124] Add ContextualTextIO

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abhiy13 commented on a change in pull request #12490:
URL: https://github.com/apache/beam/pull/12490#discussion_r467845547



##########
File path: sdks/java/io/contextual-text-io/src/main/java/org/apache/beam/sdk/io/ContextualTextIO/ContextualTextIO.java
##########
@@ -0,0 +1,554 @@
+/*
+ * 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.beam.sdk.io.ContextualTextIO;
+
+import static org.apache.beam.sdk.io.FileIO.ReadMatches.DirectoryTreatment;
+import static org.apache.beam.vendor.guava.v26_0_jre.com.google.common.base.Preconditions.checkArgument;
+import static org.apache.beam.vendor.guava.v26_0_jre.com.google.common.base.Preconditions.checkNotNull;
+
+import avro.shaded.com.google.common.collect.Iterables;
+import com.google.auto.value.AutoValue;
+import java.nio.ByteBuffer;
+import java.util.Arrays;
+import java.util.HashMap;
+import java.util.Map;
+import java.util.SortedMap;
+import java.util.TreeMap;
+import javax.annotation.Nullable;
+import org.apache.beam.sdk.coders.StringUtf8Coder;
+import org.apache.beam.sdk.io.CompressedSource;
+import org.apache.beam.sdk.io.Compression;
+import org.apache.beam.sdk.io.FileBasedSource;
+import org.apache.beam.sdk.io.FileIO;
+import org.apache.beam.sdk.io.FileIO.MatchConfiguration;
+import org.apache.beam.sdk.io.ReadAllViaFileBasedSource;
+import org.apache.beam.sdk.io.fs.EmptyMatchTreatment;
+import org.apache.beam.sdk.options.ValueProvider;
+import org.apache.beam.sdk.options.ValueProvider.StaticValueProvider;
+import org.apache.beam.sdk.schemas.NoSuchSchemaException;
+import org.apache.beam.sdk.schemas.SchemaCoder;
+import org.apache.beam.sdk.transforms.Create;
+import org.apache.beam.sdk.transforms.DoFn;
+import org.apache.beam.sdk.transforms.GroupByKey;
+import org.apache.beam.sdk.transforms.PTransform;
+import org.apache.beam.sdk.transforms.ParDo;
+import org.apache.beam.sdk.transforms.SerializableFunction;
+import org.apache.beam.sdk.transforms.View;
+import org.apache.beam.sdk.transforms.Watch.Growth.TerminationCondition;
+import org.apache.beam.sdk.transforms.display.DisplayData;
+import org.apache.beam.sdk.values.KV;
+import org.apache.beam.sdk.values.PBegin;
+import org.apache.beam.sdk.values.PCollection;
+import org.apache.beam.sdk.values.PCollectionView;
+import org.apache.beam.vendor.guava.v26_0_jre.com.google.common.annotations.VisibleForTesting;
+import org.joda.time.Duration;
+
+/**
+ * {@link PTransform}s for reading from text files with Context
+ *
+ * <h2>Reading from text files</h2>
+ *
+ * <p>To read a {@link PCollection} from one or more text files, use {@code ContextualTextIO.read()}
+ * to instantiate a transform use {@link ContextualTextIO.Read#from(String)} to specify the path of
+ * the file(s) to be read. Alternatively, if the filenames to be read are themselves in a {@link
+ * PCollection} you can use {@link FileIO} to match them and {@link ContextualTextIO#readFiles()} to
+ * read them.
+ *
+ * <p>{@link #read} returns a {@link PCollection} of {@link LineContext LineContext}, each
+ * corresponding to one line of an inout UTF-8 text file (split into lines delimited by '\n', '\r',
+ * '\r\n', or specified delimiter see {@link ContextualTextIO.Read#withDelimiter})
+ *
+ * <h3>Filepattern expansion and watching</h3>
+ *
+ * <p>By default, the filepatterns are expanded only once. The combination of {@link
+ * FileIO.Match#continuously(Duration, TerminationCondition)} and {@link #readFiles()} allow
+ * streaming of new files matching the filepattern(s).
+ *
+ * <p>By default, {@link #read} prohibits filepatterns that match no files, and {@link #readFiles()}
+ * allows them in case the filepattern contains a glob wildcard character. Use {@link
+ * ContextualTextIO.Read#withEmptyMatchTreatment} or {@link
+ * FileIO.Match#withEmptyMatchTreatment(EmptyMatchTreatment)} plus {@link #readFiles()} to configure
+ * this behavior.
+ *
+ * <p>Example 1: reading a file or filepattern.
+ *
+ * <pre>{@code
+ * Pipeline p = ...;
+ *
+ * // A simple Read of a local file (only runs locally):
+ * PCollection<LineContext> lines = p.apply(ContextualTextIO.read().from("/local/path/to/file.txt"));

Review comment:
       `@DefaultSchema(AutoValueSchema.class)`
   `@AutoValue`
   `public abstract class LineContext {`
   
   I made the class based on Schema, this should be returning an object based on a Row.
   Am I missing something ? 




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