code: package it.unibz.inf.ontop.dbschema.impl;
  
  
  /*
   * #%L
   * ontop-obdalib-core
   * %%
   * Copyright (C) 2009 - 2014 Free University of Bozen-Bolzano
   * %%
   * Licensed 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.
   * #L%
   */
  
  
  import it.unibz.inf.ontop.dbschema.QuotedID;
  
  import javax.annotation.Nonnull;
  import java.util.Objects;
  
  import static it.unibz.inf.ontop.dbschema.impl.SQLStandardQuotedIDFactory.QUOTATION_STRING;
  
  /**
   * Creates QuotedIdentifiers following the rules of PostrgeSQL:<br>
   *    - unquoted identifiers are converted into lower case<br>
   *    - quoted identifiers are preserved
   * 
   * PostgreSQL
   * ----------
   *
   * http://www.postgresql.org/docs/9.1/static/sql-syntax-lexical.html
   *
   * Unquoted names are always folded to lower (!) case.
   *
   * Quoted identifier is formed by enclosing an arbitrary sequence of characters in double-quotes (").
   * (To include a double quote, write two double quotes.)
   *
   * A variant of quoted identifiers allows including escaped Unicode characters identified by their code points.
   * This variant starts with U& (upper or lower case U followed by ampersand) immediately before the opening
   * double quote, without any spaces in between, for example U&"foo".
   *
   * @author Roman Kontchakov
   *
   */
  
  public class PostgreSQLQuotedIDFactory extends SQLStandardQuotedIDFactory {
  
  	@Override
  	protected QuotedID createFromString(@Nonnull String s) {
  		Objects.requireNonNull(s);
  
  		if (s.startsWith(QUOTATION_STRING) && s.endsWith(QUOTATION_STRING))
  			return new QuotedIDImpl(s.substring(1, s.length() - 1), QUOTATION_STRING);
  
  		return new QuotedIDImpl(s.toLowerCase(), NO_QUOTATION);
  	}
  }
  