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 com.google.common.collect.ImmutableList;
  
  /**
   * SqlHopTableFunction implements an operator for hopping.
   *
   * <p>It allows four parameters:
   *
   * <ol>
   *   <li>a table</li>
   *   <li>a descriptor to provide a watermarked column name from the input table</li>
   *   <li>an interval parameter to specify the length of window shifting</li>
   *   <li>an interval parameter to specify the length of window size</li>
   * </ol>
   */
  public class SqlHopTableFunction extends SqlWindowTableFunction {
    public SqlHopTableFunction() {
      super(SqlKind.HOP.name(), new OperandMetadataImpl());
    }
  
    /** Operand type checker for HOP. */
    private static class OperandMetadataImpl extends AbstractOperandMetadata {
      OperandMetadataImpl() {
        super(
            ImmutableList.of(PARAM_DATA, PARAM_TIMECOL, PARAM_SLIDE,
                PARAM_SIZE, PARAM_OFFSET), 4);
      }
  
      @Override public boolean checkOperandTypes(SqlCallBinding callBinding,
          boolean throwOnFailure) {
        if (!checkTableAndDescriptorOperands(callBinding, 1)) {
          return throwValidationSignatureErrorOrReturnFalse(callBinding, throwOnFailure);
        }
        if (!checkTimeColumnDescriptorOperand(callBinding, 1)) {
          return throwValidationSignatureErrorOrReturnFalse(callBinding, throwOnFailure);
        }
        if (!checkIntervalOperands(callBinding, 2)) {
          return throwValidationSignatureErrorOrReturnFalse(callBinding, throwOnFailure);
        }
        return true;
      }
  
      @Override public String getAllowedSignatures(SqlOperator op, String opName) {
        return opName + "(TABLE table_name, DESCRIPTOR(timecol), "
            + "datetime interval, datetime interval[, datetime interval])";
      }
    }
  }
  