tajo-core/src/main/java/org/apache/tajo/engine/function/string/QuoteIdent.java

/**
 * 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.tajo.engine.function.string;

import org.apache.tajo.catalog.Column;
import org.apache.tajo.common.TajoDataTypes;
import org.apache.tajo.datum.Datum;
import org.apache.tajo.datum.DatumFactory;
import org.apache.tajo.datum.NullDatum;
import org.apache.tajo.engine.function.GeneralFunction;
import org.apache.tajo.engine.function.annotation.Description;
import org.apache.tajo.engine.function.annotation.ParamTypes;
import org.apache.tajo.storage.Tuple;

/**
 * Function definition
 *
 * text quote_ident(string text)
 *
 * Description:
 * Return a quoted string.
 */
@Description(
  functionName = "quote_ident",
  description = "Return the given string suitably quoted to be used as an identifier in an SQL statement string",
  detail = "Quotes are added only if necessary "
        + "(i.e., if the string contains non-identifier characters or would be case-folded).\n"
        + "Embedded quotes are properly doubled.",
  example = "> SELECT quote_ident('Foo bar');\n"
      + "\"Foo bar\"",
  returnType = TajoDataTypes.Type.TEXT,
  paramTypes = {@ParamTypes(paramTypes = {TajoDataTypes.Type.TEXT})}
)
public class QuoteIdent extends GeneralFunction {
  public QuoteIdent() {
    super(new Column[] {
        new Column("string", TajoDataTypes.Type.TEXT)
    });
  }

  @Override
  public Datum eval(Tuple params) {
    Datum datum = params.get(0);

    if(datum instanceof NullDatum) {
      return NullDatum.get();
    }

    return DatumFactory.createText("\"" + datum.asChars() + "\"");
  }
}