content: /*
   * 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.type;
  
  import org.apache.calcite.rel.type.RelDataType;
  import org.apache.calcite.rel.type.RelDataTypeFactory;
  import org.apache.calcite.sql.SqlNode;
  
  import com.google.common.collect.ImmutableList;
  
  import java.util.Arrays;
  import java.util.List;
  
  /**
   * Strategies for inferring operand types.
   *
   * @see org.apache.calcite.sql.type.SqlOperandTypeInference
   * @see org.apache.calcite.sql.type.ReturnTypes
   */
  public abstract class InferTypes {
    private InferTypes() {}
  
    /**
     * Operand type-inference strategy where an unknown operand type is derived
     * from the first operand with a known type.
     */
    public static final SqlOperandTypeInference FIRST_KNOWN =
        (callBinding, returnType, operandTypes) -> {
          final RelDataType unknownType =
              callBinding.getValidator().getUnknownType();
          RelDataType knownType = unknownType;
          for (SqlNode operand : callBinding.operands()) {
            knownType = SqlTypeUtil.deriveType(callBinding, operand);
            if (!knownType.equals(unknownType)) {
              break;
            }
          }
  
          // REVIEW jvs 11-Nov-2008:  We can't assert this
          // because SqlAdvisorValidator produces
          // unknown types for incomplete expressions.
          // Maybe we need to distinguish the two kinds of unknown.
          //   assert !knownType.equals(unknownType);
          Arrays.fill(operandTypes, knownType);
        };
  
    /**
     * Operand type-inference strategy where an unknown operand type is derived
     * from the call's return type. If the return type is a record, it must have
     * the same number of fields as the number of operands.
     */
    public static final SqlOperandTypeInference RETURN_TYPE =
        (callBinding, returnType, operandTypes) -> {
          for (int i = 0; i < operandTypes.length; ++i) {
            operandTypes[i] =
                returnType.isStruct()
                    ? returnType.getFieldList().get(i).getType()
                    : returnType;
          }
        };
  
    /**
     * Operand type-inference strategy where an unknown operand type is assumed
     * to be boolean.
     */
    public static final SqlOperandTypeInference BOOLEAN =
        (callBinding, returnType, operandTypes) -> {
          RelDataTypeFactory typeFactory = callBinding.getTypeFactory();
          for (int i = 0; i < operandTypes.length; ++i) {
            operandTypes[i] =
                typeFactory.createSqlType(SqlTypeName.BOOLEAN);
          }
        };
  
    /**
     * Operand type-inference strategy where an unknown operand type is assumed
     * to be VARCHAR(1024).  This is not something which should be used in most
     * cases (especially since the precision is arbitrary), but for IS [NOT]
     * NULL, we don't really care about the type at all, so it's reasonable to
     * use something that every other type can be cast to.
     */
    public static final SqlOperandTypeInference VARCHAR_1024 =
        (callBinding, returnType, operandTypes) -> {
          RelDataTypeFactory typeFactory = callBinding.getTypeFactory();
          for (int i = 0; i < operandTypes.length; ++i) {
            operandTypes[i] =
                typeFactory.createSqlType(SqlTypeName.VARCHAR, 1024);
          }
        };
  
    /**
     * Operand type-inference strategy where an unknown operand type is assumed
     * to be nullable ANY.
     */
    public static final SqlOperandTypeInference ANY_NULLABLE =
        (callBinding, returnType, operandTypes) -> {
          RelDataTypeFactory typeFactory = callBinding.getTypeFactory();
          for (int i = 0; i < operandTypes.length; ++i) {
            operandTypes[i] =
                typeFactory.createTypeWithNullability(
                    typeFactory.createSqlType(SqlTypeName.ANY), true);
          }
        };
  
    /** Returns an {@link SqlOperandTypeInference} that returns a given list of
     * types. */
    public static SqlOperandTypeInference explicit(List<RelDataType> types) {
      return new ExplicitOperandTypeInference(ImmutableList.copyOf(types));
    }
  }
  