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From fhueske <...@git.apache.org>
Subject [GitHub] flink pull request #3663: [FLINK-3871] [table] Add Kafka TableSource with Av...
Date Tue, 25 Apr 2017 16:38:55 GMT
Github user fhueske commented on a diff in the pull request:

    https://github.com/apache/flink/pull/3663#discussion_r113237296
  
    --- Diff: flink-connectors/flink-connector-kafka-base/src/main/java/org/apache/flink/streaming/util/serialization/AvroRowSerializationSchema.java
---
    @@ -0,0 +1,122 @@
    +/*
    + * 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.flink.streaming.util.serialization;
    +
    +import java.io.ByteArrayOutputStream;
    +import java.io.IOException;
    +import java.util.List;
    +import org.apache.avro.Schema;
    +import org.apache.avro.generic.GenericData;
    +import org.apache.avro.generic.GenericRecord;
    +import org.apache.avro.io.DatumWriter;
    +import org.apache.avro.io.Encoder;
    +import org.apache.avro.io.EncoderFactory;
    +import org.apache.avro.reflect.ReflectDatumWriter;
    +import org.apache.avro.specific.SpecificData;
    +import org.apache.avro.specific.SpecificRecord;
    +import org.apache.avro.util.Utf8;
    +import org.apache.flink.types.Row;
    +import org.apache.flink.util.Preconditions;
    +
    +/**
    + * Serialization schema that serializes {@link Row} over {@link SpecificRecord} into
a Avro bytes.
    + */
    +public class AvroRowSerializationSchema implements SerializationSchema<Row> {
    +
    +	/**
    +	 * Avro serialization schema.
    +	 */
    +	private final Schema schema;
    +
    +	/**
    +	 * Writer to serialize Avro record into a byte array.
    +	 */
    +	private final DatumWriter<GenericRecord> datumWriter;
    +
    +	/**
    +	 * Output stream to serialize records into byte array.
    +	 */
    +	private final ByteArrayOutputStream arrayOutputStream =  new ByteArrayOutputStream();
    +
    +	/**
    +	 * Low-level class for serialization of Avro values.
    +	 */
    +	private final Encoder encoder = EncoderFactory.get().binaryEncoder(arrayOutputStream,
null);
    +
    +	/**
    +	 * Creates a Avro serialization schema for the given schema.
    +	 *
    +	 * @param recordClazz Avro record class used to deserialize Avro's record to Flink's
row
    +	 */
    +	@SuppressWarnings("unchecked")
    +	public AvroRowSerializationSchema(Class<? extends SpecificRecord> recordClazz)
{
    +		Preconditions.checkNotNull(recordClazz, "Avro record class must not be null.");
    +		this.schema = SpecificData.get().getSchema(recordClazz);
    +		this.datumWriter = new ReflectDatumWriter<>(schema);
    +	}
    +
    +	@Override
    +	@SuppressWarnings("unchecked")
    +	public byte[] serialize(Row row) {
    +		// convert to record
    +		final Object record = convertToRecord(schema, row);
    +
    +		// write
    +		try {
    +			arrayOutputStream.reset();
    +			datumWriter.write((GenericRecord) record, encoder);
    +			encoder.flush();
    +			return arrayOutputStream.toByteArray();
    +		} catch (IOException e) {
    +			throw new RuntimeException("Failed to serialize Row.", e);
    +		}
    +	}
    +
    +	/**
    +	 * Converts a (nested) Flink Row into Avro's {@link GenericRecord}.
    +	 * Strings are converted into Avro's {@link Utf8} fields.
    +	 */
    +	private static Object convertToRecord(Schema schema, Object rowObj) {
    +		if (rowObj instanceof Row) {
    +			// records can be wrapped in a union
    +			if (schema.getType() == Schema.Type.UNION) {
    +				final List<Schema> types = schema.getTypes();
    +				if (types.size() == 2 && types.get(0).getType() == Schema.Type.NULL &&
types.get(1).getType() == Schema.Type.RECORD) {
    --- End diff --
    
    This limitation exists because the Table API cannot handle UNION types either, right?
    Isn't this the same as having a nullable record field?


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