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;
  
  import org.apache.calcite.sql.parser.SqlParserPos;
  import org.apache.calcite.sql.type.OperandTypes;
  import org.apache.calcite.sql.type.ReturnTypes;
  import org.apache.calcite.sql.validate.SqlValidator;
  import org.apache.calcite.sql.validate.SqlValidatorScope;
  import org.apache.calcite.util.ImmutableNullableList;
  
  import org.checkerframework.checker.nullness.qual.Nullable;
  
  import static com.google.common.base.Preconditions.checkArgument;
  
  import static org.apache.calcite.util.Static.RESOURCE;
  
  /**
   * An operator that decides how to handle null input
   * ({@code RESPECT NULLS} and {@code IGNORE NULLS}).
   *
   * <p>Currently, only the windowed aggregate functions {@code FIRST_VALUE},
   * {@code LAST_VALUE}, {@code LEAD} and {@code LAG} support it.
   *
   * @see SqlAggFunction#allowsNullTreatment()
   */
  public class SqlNullTreatmentOperator extends SqlSpecialOperator {
    public SqlNullTreatmentOperator(SqlKind kind) {
      super(kind.sql, kind, 20, true, ReturnTypes.ARG0, null, OperandTypes.ANY);
      checkArgument(kind == SqlKind.RESPECT_NULLS
          || kind == SqlKind.IGNORE_NULLS);
    }
  
    @Override public SqlCall createCall(@Nullable SqlLiteral functionQualifier,
        SqlParserPos pos, @Nullable SqlNode... operands) {
      // As super.createCall, but don't union the positions
      return new SqlBasicCall(this, ImmutableNullableList.copyOf(operands), pos,
          functionQualifier);
    }
  
    @Override public void unparse(SqlWriter writer, SqlCall call, int leftPrec,
        int rightPrec) {
      assert call.operandCount() == 1;
      call.operand(0).unparse(writer, getLeftPrec(), getRightPrec());
      writer.keyword(getName());
    }
  
    @Override public void validateCall(
        SqlCall call,
        SqlValidator validator,
        SqlValidatorScope scope,
        SqlValidatorScope operandScope) {
      assert call.getOperator() == this;
      assert call.operandCount() == 1;
      SqlCall aggCall = call.operand(0);
      if (!aggCall.getOperator().isAggregator()
          || !((SqlAggFunction) aggCall.getOperator()).allowsNullTreatment()) {
        throw validator.newValidationError(aggCall,
            RESOURCE.disallowsNullTreatment(aggCall.getOperator().getName()));
      }
    }
  }
  