core/src/main/java/org/apache/calcite/sql/SqlUnresolvedFunction.java

/*
 * 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.calcite.sql;

import org.apache.calcite.rel.type.RelDataType;
import org.apache.calcite.rel.type.RelDataTypeFactory;
import org.apache.calcite.sql.type.SqlOperandTypeChecker;
import org.apache.calcite.sql.type.SqlOperandTypeInference;
import org.apache.calcite.sql.type.SqlReturnTypeInference;
import org.apache.calcite.sql.type.SqlTypeName;

import org.checkerframework.checker.nullness.qual.Nullable;

import java.util.List;

/**
 * Placeholder for an unresolved function.
 *
 * <p>Created by the parser, then it is rewritten to proper SqlFunction by
 * the validator to a function defined in a Calcite schema.
 */
public class SqlUnresolvedFunction extends SqlFunction {
  /**
   * Creates a placeholder SqlUnresolvedFunction for an invocation of a function
   * with a possibly qualified name. This name must be resolved into either
   * a builtin function or a user-defined function.
   *
   * @param sqlIdentifier        possibly qualified identifier for function
   * @param returnTypeInference  strategy to use for return type inference
   * @param operandTypeInference strategy to use for parameter type inference
   * @param operandTypeChecker   strategy to use for parameter type checking
   * @param paramTypes           array of parameter types
   * @param funcType             function category
   */
  public SqlUnresolvedFunction(
      SqlIdentifier sqlIdentifier,
      @Nullable SqlReturnTypeInference returnTypeInference,
      @Nullable SqlOperandTypeInference operandTypeInference,
      @Nullable SqlOperandTypeChecker operandTypeChecker,
      @Nullable List<RelDataType> paramTypes,
      SqlFunctionCategory funcType) {
    super(sqlIdentifier, returnTypeInference, operandTypeInference,
        operandTypeChecker, paramTypes, funcType);
  }

  /**
   * {@inheritDoc}T
   *
   * <p>The operator class for this function isn't resolved to the
   * correct class. This happens in the case of user defined
   * functions. Return the return type to be 'ANY', so we don't
   * fail.
   */
  @Override public RelDataType inferReturnType(SqlOperatorBinding opBinding) {
    final RelDataTypeFactory typeFactory = opBinding.getTypeFactory();
    return typeFactory.createTypeWithNullability(
        typeFactory.createSqlType(SqlTypeName.ANY), true);
  }
}