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.dialect;
  
  import org.apache.calcite.rel.type.RelDataTypeSystem;
  import org.apache.calcite.sql.SqlDialect;
  import org.apache.calcite.sql.SqlIntervalLiteral;
  import org.apache.calcite.sql.SqlIntervalQualifier;
  import org.apache.calcite.sql.SqlWriter;
  
  /**
   * A <code>SqlDialect</code> implementation for the IBM DB2 database.
   */
  public class Db2SqlDialect extends SqlDialect {
    public static final SqlDialect.Context DEFAULT_CONTEXT = SqlDialect.EMPTY_CONTEXT
        .withDatabaseProduct(SqlDialect.DatabaseProduct.DB2);
  
    public static final SqlDialect DEFAULT = new Db2SqlDialect(DEFAULT_CONTEXT);
  
    /** Creates a Db2SqlDialect. */
    public Db2SqlDialect(Context context) {
      super(context);
    }
  
    @Override public boolean supportsCharSet() {
      return false;
    }
  
    @Override public boolean hasImplicitTableAlias() {
      return false;
    }
  
    @Override public void unparseSqlIntervalQualifier(SqlWriter writer,
        SqlIntervalQualifier qualifier, RelDataTypeSystem typeSystem) {
  
      // DB2 supported qualifiers. Singular form of these keywords are also acceptable.
      // YEAR/YEARS
      // MONTH/MONTHS
      // DAY/DAYS
      // HOUR/HOURS
      // MINUTE/MINUTES
      // SECOND/SECONDS
  
      switch (qualifier.timeUnitRange) {
      case YEAR:
      case MONTH:
      case DAY:
      case HOUR:
      case MINUTE:
      case SECOND:
      case MICROSECOND:
        final String timeUnit = qualifier.timeUnitRange.startUnit.name();
        writer.keyword(timeUnit);
        break;
      default:
        throw new AssertionError("Unsupported type: " + qualifier.timeUnitRange);
      }
  
      if (null != qualifier.timeUnitRange.endUnit) {
        throw new AssertionError("Unsupported end unit: "
            + qualifier.timeUnitRange.endUnit);
      }
    }
  
    @Override public void unparseSqlIntervalLiteral(SqlWriter writer,
        SqlIntervalLiteral literal, int leftPrec, int rightPrec) {
      // A duration is a positive or negative number representing an interval of time.
      // If one operand is a date, the other labeled duration of YEARS, MONTHS, or DAYS.
      // If one operand is a time, the other must be labeled duration of HOURS, MINUTES, or SECONDS.
      // If one operand is a timestamp, the other operand can be any of teh duration.
  
      SqlIntervalLiteral.IntervalValue interval =
          literal.getValueAs(SqlIntervalLiteral.IntervalValue.class);
      if (interval.getSign() == -1) {
        writer.print("-");
      }
      writer.literal(interval.getIntervalLiteral());
      unparseSqlIntervalQualifier(writer, interval.getIntervalQualifier(),
          RelDataTypeSystem.DEFAULT);
    }
  
  }
  