Flink HCatalog

<dependency>
    <groupId>org.apache.flink</groupId>
    <artifactId>flink-hcatalog_2.11</artifactId>
    <version>1.14.6</version>
</dependency>

import org.apache.flink.hcatalog.java.HCatInputFormat;
import org.apache.flink.hcatalog.HCatInputFormatBase;
import org.apache.hadoop.conf.Configuration;
import org.apache.hive.hcatalog.data.HCatRecord;
import org.apache.hive.hcatalog.data.schema.HCatSchema;
import org.apache.hive.hcatalog.data.schema.HCatFieldSchema;
import org.apache.hive.hcatalog.common.HCatException;

import org.apache.flink.hcatalog.scala.HCatInputFormat
import org.apache.hadoop.conf.Configuration
import org.apache.hive.hcatalog.data.HCatRecord

import org.apache.flink.api.java.ExecutionEnvironment;
import org.apache.flink.api.java.DataSet;
import org.apache.flink.hcatalog.java.HCatInputFormat;
import org.apache.hive.hcatalog.data.HCatRecord;

// Create execution environment
ExecutionEnvironment env = ExecutionEnvironment.getExecutionEnvironment();

// Create HCatalog input format
HCatInputFormat<HCatRecord> hCatFormat = new HCatInputFormat<>("mydb", "mytable");

// Optional: Project specific fields
hCatFormat.getFields("name", "age", "city");

// Optional: Apply partition filter
hCatFormat.withFilter("year=2023 AND month='01'");

// Create DataSet and process
DataSet<HCatRecord> input = env.createInput(hCatFormat);

import org.apache.flink.api.scala._
import org.apache.flink.hcatalog.scala.HCatInputFormat
import org.apache.hive.hcatalog.data.HCatRecord

// Create execution environment
val env = ExecutionEnvironment.getExecutionEnvironment

// Create HCatalog input format with field projection
val hCatFormat = new HCatInputFormat[HCatRecord]("mydb", "mytable")
  .getFields("name", "age", "city")
  .withFilter("year=2023")

// Create DataSet
val input = env.createInput(hCatFormat)

/**
 * Java HCatalog input format for reading from Hive tables
 * Supports conversion to Flink Tuples (up to 25 fields) or HCatRecord objects
 */
public class HCatInputFormat<T> extends HCatInputFormatBase<T> {
    public HCatInputFormat();
    public HCatInputFormat(String database, String table) throws Exception;
    public HCatInputFormat(String database, String table, Configuration config) throws Exception;
}

// Reading as HCatRecord (default)
HCatInputFormat<HCatRecord> recordFormat = new HCatInputFormat<>("sales", "transactions");

// Reading as Flink Tuple
HCatInputFormat<Tuple3<String, Integer, Double>> tupleFormat = 
    new HCatInputFormat<Tuple3<String, Integer, Double>>("sales", "transactions")
        .getFields("product_name", "quantity", "price")
        .asFlinkTuples();

/**
 * Scala HCatalog input format for reading from Hive tables
 * Supports conversion to Scala tuples (up to 22 fields) or HCatRecord objects
 */
class HCatInputFormat[T](database: String, table: String, config: Configuration) 
    extends HCatInputFormatBase[T](database, table, config) {
  def this(database: String, table: String) {
    this(database, table, new Configuration)
  }
}

// Reading as HCatRecord (default)
val recordFormat = new HCatInputFormat[HCatRecord]("sales", "transactions")

// Reading as Scala Tuple
val tupleFormat = new HCatInputFormat[(String, Int, Double)]("sales", "transactions")
  .getFields("product_name", "quantity", "price")
  .asFlinkTuples()

/**
 * Specifies the fields which are returned by the InputFormat and their order
 * @param fields The fields and their order which are returned by the InputFormat
 * @return This InputFormat with specified return fields
 * @throws IOException if field projection fails
 */
public HCatInputFormatBase<T> getFields(String... fields) throws IOException;

// Java: Select specific fields
hCatFormat.getFields("customer_id", "order_date", "total_amount");

// Java: Reorder fields
hCatFormat.getFields("total_amount", "customer_id", "order_date");

// Scala: Select specific fields
hCatFormat.getFields("customer_id", "order_date", "total_amount")

// Scala: Reorder fields  
hCatFormat.getFields("total_amount", "customer_id", "order_date")

/**
 * Specifies a SQL-like filter condition on the table's partition columns
 * Filter conditions on non-partition columns are invalid
 * @param filter A SQL-like filter condition on the table's partition columns
 * @return This InputFormat with specified partition filter
 * @throws IOException if filter application fails
 */
public HCatInputFormatBase<T> withFilter(String filter) throws IOException;

// Java: Single partition filter
hCatFormat.withFilter("year=2023");

// Java: Multiple partition conditions
hCatFormat.withFilter("year=2023 AND month='12' AND day>=15");

// Java: Range and comparison operators
hCatFormat.withFilter("year>=2020 AND region IN ('US', 'EU')");

// Scala: Single partition filter
hCatFormat.withFilter("year=2023")

// Scala: Multiple partition conditions
hCatFormat.withFilter("year=2023 AND month='12' AND day>=15")

/**
 * Specifies that the InputFormat returns Flink tuples instead of HCatRecord
 * Note: Flink tuples might only support a limited number of fields (depending on the API)
 * @return This InputFormat configured to return tuples
 * @throws HCatException if tuple conversion setup fails
 */
public HCatInputFormatBase<T> asFlinkTuples() throws HCatException;

// Java: Convert to Flink Tuple (up to 25 fields)
HCatInputFormat<Tuple2<String, Integer>> tupleFormat = 
    new HCatInputFormat<Tuple2<String, Integer>>("mydb", "mytable")
        .getFields("name", "age")
        .asFlinkTuples();

// Scala: Convert to Scala tuple (up to 22 fields)
val tupleFormat = new HCatInputFormat[(String, Int)]("mydb", "mytable")
  .getFields("name", "age")
  .asFlinkTuples()

/**
 * Returns the Hadoop Configuration of the HCatInputFormat
 * @return The Configuration of the HCatInputFormat
 */
public Configuration getConfiguration();

// Access configuration for customization
Configuration config = hCatFormat.getConfiguration();
config.set("hive.metastore.uris", "thrift://metastore:9083");
config.setInt("mapreduce.input.fileinputformat.split.minsize", 1024000);

/**
 * Returns the HCatSchema of the HCatRecord returned by this InputFormat
 * @return The HCatSchema of the HCatRecords returned by this InputFormat
 */
public HCatSchema getOutputSchema();

// Inspect table schema
HCatSchema schema = hCatFormat.getOutputSchema();
List<HCatFieldSchema> fields = schema.getFields();
for (HCatFieldSchema field : fields) {
    System.out.println("Field: " + field.getName() + ", Type: " + field.getType());
}

/**
 * Abstract base class for HCatalog input formats
 * Provides common functionality for reading from HCatalog tables
 */
public abstract class HCatInputFormatBase<T> extends RichInputFormat<T, HadoopInputSplit>
        implements ResultTypeQueryable<T> {
    
    protected HCatInputFormatBase();
    protected HCatInputFormatBase(String database, String table) throws IOException;
    protected HCatInputFormatBase(String database, String table, Configuration config) throws IOException;
    
    // Abstract methods to be implemented by language-specific subclasses
    protected abstract int getMaxFlinkTupleSize();
    protected abstract T buildFlinkTuple(T t, HCatRecord record) throws HCatException;
}

/**
 * Hadoop input split wrapper for Flink integration
 */
class HadoopInputSplit implements InputSplit {
    // Implementation details handled internally
}

/**
 * HCatalog record representing a row of data from Hive table
 * Contains field values accessible by name or position
 */
interface HCatRecord {
    Object get(String fieldName, HCatSchema schema);
    Object get(int fieldPos);
    List<Object> getAll();
    // Additional methods for data access
}

/**
 * Schema definition for HCatalog table structure
 * Contains field definitions and metadata
 */
class HCatSchema {
    List<HCatFieldSchema> getFields();
    HCatFieldSchema get(String fieldName);
    HCatFieldSchema get(int position);
    int getPosition(String fieldName);
    List<String> getFieldNames();
    // Additional schema methods
}

/**
 * Individual field schema definition
 */
class HCatFieldSchema {
    String getName();
    Type getType();
    String getComment();
    // Additional field metadata methods
    
    enum Type {
        INT, TINYINT, SMALLINT, BIGINT, BOOLEAN, FLOAT, DOUBLE, 
        STRING, BINARY, ARRAY, MAP, STRUCT
    }
}

try {
    HCatInputFormat<HCatRecord> format = new HCatInputFormat<>("mydb", "mytable");
    format.withFilter("year=2023");
    format.getFields("name", "age", "salary");
} catch (IOException e) {
    // Handle configuration or connection errors
    logger.error("Failed to configure HCatalog input: " + e.getMessage());
} catch (HCatException e) {
    // Handle HCatalog-specific errors
    logger.error("HCatalog error: " + e.getMessage());
}