LookupFunctionProvider

LookupableTableSource.java

import org.apache.flink.annotation.Experimental;

/**
 * A {@link TableSource} which supports for lookup accessing via key column(s).
 * For example, MySQL TableSource can implement this interface to support lookup accessing.
 * When temporal join this MySQL table, the runtime behavior could be in a lookup fashion.
 *
 * @param <T> type of the result
 */
@Experimental
public interface LookupableTableSource<T> extends TableSource<T> {

	/**
	 * Gets the {@link LookupFunctionProvider} which is a factory to create a lookup function
	 * instance.
	 * @see LookupFunctionProvider
	 */
	LookupFunctionProvider getLookupFunctionProvider();
}

LookupFunctionProvider.java

import org.apache.flink.table.functions.AsyncTableFunction;
import org.apache.flink.table.functions.TableFunction;

/**
 * A base factory interface to create a lookup function. A lookup function is used to query table
 * via key column(s). See {@link LookupableTableSource} for more information.
 *
 * <p>Currently, a lookup factory can either be {@link TableFunctionProvider} or
 * {@link AsyncTableFunction}.
 */
public interface LookupFunctionProvider {

	/**
	 * A concrete factory interface of {@link LookupFunctionProvider}.
	 * The {@link TableFunctionProvider} is used to create a {@link TableFunction} instance to
	 * lookup table contents via key columns.
	 *
	 * @param <T> type of the result
	 */
	interface TableFunctionProvider<T> extends LookupFunctionProvider {

		/**
		 * Creates a {@link TableFunction} instance which supports lookup one key at a time.
		 * @param lookupKeys the chosen field names as lookup keys, it is in the defined order
		 *                   of schema.
		 */
		TableFunction<T> createLookupFunction(String[] lookupKeys);
	}

	/**
	 * A concrete factory interface of {@link LookupFunctionProvider}.
	 * The {@link AsyncTableFunctionProvider} is used to create an {@link AsyncTableFunction}
	 * instance to async lookup table contents via key columns.
	 *
	 * @param <T> type of the result
	 */
	interface AsyncTableFunctionProvider<T> extends LookupFunctionProvider {

		/**
		 * Creates a {@link AsyncTableFunction} instance which supports async lookup one key
		 * at a time.
		 * @param lookupKeys the chosen field names as lookup keys, it is in the defined order
		 *                   of schema.
		 */
		AsyncTableFunction<T> createLookupFunction(String[] lookupKeys);
	}

	/**
	 * Utility method to create a {@link TableFunctionProvider} from a {@link TableFunction}
	 * instance.
	 */
	static <T> TableFunctionProvider<T> of(TableFunction<T> lookupFunction) {
		return lookupKeys -> lookupFunction;
	}

	/**
	 * Utility method to create a {@link AsyncTableFunctionProvider} from a
	 * {@link AsyncTableFunction} instance.
	 */
	static <T> AsyncTableFunctionProvider<T> of(AsyncTableFunction<T> lookupFunction) {
		return lookupKeys -> lookupFunction;
	}

}