org.apache.flink.table.api.functions.CustomTypeDefinedFunction Maven / Gradle / Ivy
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* Licensed to the Apache Software Foundation (ASF) under one
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* 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,
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* See the License for the specific language governing permissions and
* limitations under the License.
*/
package org.apache.flink.table.api.functions;
import org.apache.flink.api.common.functions.InvalidTypesException;
import org.apache.flink.table.api.ValidationException;
import org.apache.flink.table.types.DataType;
import org.apache.flink.table.types.DataTypes;
/**
* {@link UserDefinedFunction} to define its parameterTypes.
*/
public abstract class CustomTypeDefinedFunction extends UserDefinedFunction {
/**
* Returns {@link DataType} about the operands of the evaluation method with a given
* signature.
*
* In order to perform operand type inference in SQL (especially when NULL is used) it might
* be necessary to determine the parameter {@link DataType} 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 DataType} of operand types
*/
public DataType[] getParameterTypes(Class[] signature) {
DataType[] types = new DataType[signature.length];
try {
for (int i = 0; i < signature.length; i++) {
types[i] = DataTypes.extractDataType(signature[i]);
}
} catch (InvalidTypesException e) {
throw new ValidationException("Parameter types of scalar function '" +
getClass().getCanonicalName() + "' cannot be automatically determined. " +
"Please provide data type manually.");
}
return types;
}
/**
* Returns the result type of the evaluation method with a given signature.
*
*
This method needs to be overriden in case Flink's type extraction facilities are not
* sufficient to extract the [[DataType]] 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.
*
*
The input arguments are the input arguments which are passed to the eval() method.
* Only the literal arguments (constant values) are passed to the [[getResultType()]] method.
* If non-literal arguments appear, it will pass nulls instead.
*
*
The argument types are also passed to the method. These argument types would allow to
* determine the return type based on the used eval() method.
*
* @param arguments arguments of a function call (only literal arguments
* are passed, nulls for non-literal ones)
* @param argTypes The classes of the arguments of the called eval() method.
* @return [[DataType]] of result type or null if Flink should determine the type
*/
public DataType getResultType(Object[] arguments, Class[] argTypes) {
return null;
}
}