[FLINK-10689] [table] Port UDF interfaces to flink-table-common

This commit ports all UDF extension points to Java and relocates them
to flink-table-common. Projects that just want to provide functions
don't need to import flink-table and thus Scala anymore.

This closes apache#7059.

flink-end-to-end-tests/flink-sql-client-test/pom.xml

@@ -33,7 +33,7 @@ under the License.
  <dependencies>
  <dependency>
  <groupId>org.apache.flink</groupId>
- <artifactId>flink-table_${scala.binary.version}</artifactId>
+ <artifactId>flink-table-common</artifactId>
  <version>${project.version}</version>
  <scope>provided</scope>
  </dependency>

flink-libraries/flink-table-common/src/main/java/org/apache/flink/table/functions/AggregateFunction.java

@@ -0,0 +1,115 @@
+/*
+ * 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:https://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.table.functions;
+
+import org.apache.flink.annotation.PublicEvolving;
+import org.apache.flink.api.common.typeinfo.TypeInformation;
+
+/**
+ * Base class for User-Defined Aggregates.
+ *
+ * <p>The behavior of an {@link AggregateFunction} can be defined by implementing a series of custom
+ * methods. An {@link AggregateFunction} needs at least three methods:
+ * - createAccumulator,
+ * - accumulate, and
+ * - getValue.
+ *
+ * <p>There are a few other methods that can be optional to have:
+ * - retract,
+ * - merge, and
+ * - resetAccumulator
+ *
+ * <p>All these methods must be declared publicly, not static and named exactly as the names
+ * mentioned above. The methods createAccumulator and getValue are defined in the
+ * {@link AggregateFunction} functions, while other methods are explained below.
+ *
+ * <p>Processes the input values and update the provided accumulator instance. The method
+ * accumulate can be overloaded with different custom types and arguments. An AggregateFunction
+ * requires at least one accumulate() method.
+ *
+ *
+ * <p>Retracts the input values from the accumulator instance. The current design assumes the
+ * inputs are the values that have been previously accumulated. The method retract can be
+ * overloaded with different custom types and arguments. This function must be implemented for
+ * datastream bounded over aggregate.
+ *
+ * <p>Merges a group of accumulator instances into one accumulator instance. This function must be
+ * implemented for datastream session window grouping aggregate and dataset grouping aggregate.
+ *
+ * <p>Resets the accumulator for this {@link AggregateFunction}. This function must be implemented for
+ * dataset grouping aggregate.
+ *
+ *
+ * @param T the type of the aggregation result
+ * @param ACC the type of the aggregation accumulator. The accumulator is used to keep the
+ * aggregated values which are needed to compute an aggregation result.
+ * AggregateFunction represents its state using accumulator, thereby the state of the
+ * AggregateFunction must be put into the accumulator.
+ */
+@PublicEvolving
+public abstract class AggregateFunction<T, ACC> extends UserDefinedFunction {
+
+ /**
+ * Creates and init the Accumulator for this {@link AggregateFunction}.
+ *
+ * @return the accumulator with the initial value
+ */
+ public abstract ACC createAccumulator();
+
+ /**
+ * Called every time when an aggregation result should be materialized.
+ * The returned value could be either an early and incomplete result
+ * (periodically emitted as data arrive) or the final result of the
+ * aggregation.
+ *
+ * @param accumulator the accumulator which contains the current
+ * aggregated results
+ * @return the aggregation result
+ */
+ public abstract T getValue(ACC accumulator);
+
+ /**
+ * Returns true if this AggregateFunction can only be applied in an OVER window.
+ *
+ * @return true if the AggregateFunction requires an OVER window, false otherwise.
+ */
+ public boolean requiresOver() {
+ return false;
+ }
+
+ /**
+ * Returns the TypeInformation of the AggregateFunction's result.
+ *
+ * @return The TypeInformation of the AggregateFunction's result or null if the result type
+ * should be automatically inferred.
+ */
+ public TypeInformation<T> getResultType() {
+ return null;
+ }
+
+ /**
+ * Returns the TypeInformation of the AggregateFunction's accumulator.
+ *
+ * @return The TypeInformation of the AggregateFunction's accumulator or null if the
+ * accumulator type should be automatically inferred.
+ */
+ public TypeInformation<ACC> getAccumulatorType() {
+ return null;
+ }
+}

flink-libraries/flink-table-common/src/main/java/org/apache/flink/table/functions/FunctionContext.java

@@ -0,0 +1,80 @@
+/*
+ * 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:https://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.table.functions;
+
+import org.apache.flink.annotation.PublicEvolving;
+import org.apache.flink.api.common.ExecutionConfig.GlobalJobParameters;
+import org.apache.flink.api.common.functions.RuntimeContext;
+import org.apache.flink.metrics.MetricGroup;
+
+import java.io.File;
+
+/**
+ * A FunctionContext allows to obtain global runtime information about the context in which the
+ * user-defined function is executed. The information include the metric group,
+ * the distributed cache files, and the global job parameters.
+ */
+@PublicEvolving
+public class FunctionContext {
+
+ /**
+ * @param context the runtime context in which the Flink Function is executed
+ */
+ private RuntimeContext context;
+
+ public FunctionContext(RuntimeContext context) {
+ this.context = context;
+ }
+
+ /**
+ * Returns the metric group for this parallel subtask.
+ *
+ * @return metric group for this parallel subtask.
+ */
+ public MetricGroup getMetricGroup() {
+ return context.getMetricGroup();
+ }
+
+ /**
+ * Gets the local temporary file copy of a distributed cache files.
+ *
+ * @param name distributed cache file name
+ * @return local temporary file copy of a distributed cache file.
+ */
+ public File getCachedFile(String name) {
+ return context.getDistributedCache().getFile(name);
+ }
+
+ /**
+ * Gets the global job parameter value associated with the given key as a string.
+ *
+ * @param key key pointing to the associated value
+ * @param defaultValue default value which is returned in case global job parameter is null
+ * or there is no value associated with the given key
+ * @return (default) value associated with the given key
+ */
+ public String getJobParameter(String key, String defaultValue) {
+ GlobalJobParameters conf = context.getExecutionConfig().getGlobalJobParameters();
+ if (conf != null && conf.toMap().containsKey(key)) {
+ return conf.toMap().get(key);
+ } else {
+ return defaultValue;
+ }
+ }
+}

flink-libraries/flink-table-common/src/main/java/org/apache/flink/table/functions/ScalarFunction.java

@@ -0,0 +1,95 @@
+/*
+ * 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:https://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.table.functions;
+
+import org.apache.flink.annotation.PublicEvolving;
+import org.apache.flink.api.common.functions.InvalidTypesException;
+import org.apache.flink.api.common.typeinfo.TypeInformation;
+import org.apache.flink.api.java.typeutils.TypeExtractor;
+import org.apache.flink.table.api.ValidationException;
+
+import java.util.Arrays;
+import java.util.List;
+import java.util.stream.Collectors;
+
+/**
+ * Base class for a user-defined scalar function. A user-defined scalar functions maps zero, one,
+ * or multiple scalar values to a new scalar value.
+ *
+ * <p>The behavior of a {@link ScalarFunction} can be defined by implementing a custom evaluation
+ * method. An evaluation method must be declared publicly and named "eval". Evaluation methods
+ * can also be overloaded by implementing multiple methods named "eval".
+ *
+ * <p>User-defined functions must have a default constructor and must be instantiable during runtime.
+ *
+ * <p>By default the result type of an evaluation method is determined by Flink's type extraction
+ * facilities. This is sufficient for basic types or simple POJOs but might be wrong for more
+ * complex, custom, or composite types. In these cases {@link TypeInformation} of the result type
+ * can be manually defined by overriding {@link ScalarFunction#getResultType}.
+ *
+ * <p>Internally, the Table/SQL API code generation works with primitive values as much as possible.
+ * If a user-defined scalar function should not introduce much overhead during runtime, it is
+ * recommended to declare parameters and result types as primitive types instead of their boxed
+ * classes. DATE/TIME is equal to int, TIMESTAMP is equal to long.
+ */
+@PublicEvolving
+public abstract class ScalarFunction extends UserDefinedFunction {
+
+ /**
+ * Returns the result type of the evaluation method with a given signature.
+ *
+ * <p>This method needs to be overridden in case Flink's type extraction facilities are not
+ * sufficient to extract the {@link TypeInformation} based on the return type of the evaluation
+ * method. Flink's type extraction facilities can handle basic types or
+ * simple POJOs but might be wrong for more complex, custom, or composite types.
+ *
+ * @param signature signature of the method the return type needs to be determined
+ * @return {@link TypeInformation} of result type or null if Flink should determine the type
+ */
+ public TypeInformation<?> getResultType(Class<?>[] signature) {
+ return null;
+ }
+
+ /**
+ * Returns {@link TypeInformation} about the operands of the evaluation method with a given
+ * signature.
+ *
+ * <p>In order to perform operand type inference in SQL (especially when NULL is used) it might be
+ * necessary to determine the parameter {@link TypeInformation} of an evaluation method.
+ * By default Flink's type extraction facilities are used for this but might be wrong for
+ * more complex, custom, or composite types.
+ *
+ * @param signature signature of the method the operand types need to be determined
+ * @return {@link TypeInformation} of operand types
+ */
+ public TypeInformation<?>[] getParameterTypes(Class<?>[] signature) {
+
+ List<TypeInformation<?>> typeList = Arrays.asList(signature).stream().map(c -> {
+ try {
+ return TypeExtractor.getForClass(c);
+ } catch (InvalidTypesException e) {
+ throw new ValidationException(
+ "Parameter types of table function " + this.getClass().getCanonicalName() + " cannot be " +
+ "automatically determined. Please provide type information manually.");
+ }
+ }).collect(Collectors.toList());
+
+ return typeList.toArray(new TypeInformation<?>[0]);
+ }
+}