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.fun;
  
  import org.apache.calcite.rel.type.RelDataType;
  import org.apache.calcite.rel.type.RelDataTypeFactory;
  import org.apache.calcite.sql.SqlCall;
  import org.apache.calcite.sql.SqlIdentifier;
  import org.apache.calcite.sql.SqlKind;
  import org.apache.calcite.sql.SqlNode;
  import org.apache.calcite.sql.SqlSpecialOperator;
  import org.apache.calcite.sql.SqlWriter;
  import org.apache.calcite.sql.type.SqlTypeName;
  import org.apache.calcite.sql.validate.SqlValidator;
  import org.apache.calcite.sql.validate.SqlValidatorScope;
  
  import java.util.List;
  
  /** Operator that returns the current or next value of a sequence. */
  public class SqlSequenceValueOperator extends SqlSpecialOperator {
    /** Creates a SqlSequenceValueOperator. */
    SqlSequenceValueOperator(SqlKind kind) {
      super(kind.name(), kind, 100);
      assert kind == SqlKind.NEXT_VALUE || kind == SqlKind.CURRENT_VALUE;
    }
  
    @Override public boolean isDeterministic() {
      return false;
    }
  
    @Override public void unparse(SqlWriter writer, SqlCall call, int leftPrec,
        int rightPrec) {
      writer.sep(kind == SqlKind.NEXT_VALUE
          ? "NEXT VALUE FOR" : "CURRENT VALUE FOR");
      call.getOperandList().get(0).unparse(writer, 0, 0);
    }
  
    @Override public RelDataType deriveType(SqlValidator validator,
        SqlValidatorScope scope, SqlCall call) {
      final RelDataTypeFactory typeFactory = validator.getTypeFactory();
      return typeFactory.createTypeWithNullability(
          typeFactory.createSqlType(SqlTypeName.BIGINT), false);
    }
  
    @Override public void validateCall(SqlCall call, SqlValidator validator,
        SqlValidatorScope scope, SqlValidatorScope operandScope) {
      List<SqlNode> operands = call.getOperandList();
      assert operands.size() == 1;
      assert operands.get(0) instanceof SqlIdentifier;
      SqlIdentifier id = (SqlIdentifier) operands.get(0);
      validator.validateSequenceValue(scope, id);
    }
  }
  