/*
BEGIN LICENSE BLOCK
Copyright 2010-2011, Heiko Mueller, Sam Lindley, James Cheney and
University of Edinburgh
This file is part of Database Wiki.
Database Wiki is free software: you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation, either version 3 of the License, or
(at your option) any later version.
Database Wiki is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU General Public License for more details.
You should have received a copy of the GNU General Public License
along with Database Wiki. If not, see <http://www.gnu.org/licenses/>.
END LICENSE BLOCK
*/
package org.dbwiki.data.query;
/** A XAQLQueryStatement consisting of a reference to the database and the XAQLQuery definition.
* Represents query statements for XAQL queries.
*
* @author hmueller
*
*/
import org.dbwiki.data.database.Database;
import org.dbwiki.data.database.DatabaseAttributeNode;
import org.dbwiki.data.database.DatabaseElementNode;
import org.dbwiki.data.database.DatabaseGroupNode;
import org.dbwiki.data.database.DatabaseTextNode;
import org.dbwiki.data.index.DatabaseContent;
import org.dbwiki.data.query.handler.QueryNodeHandler;
import org.dbwiki.data.query.xaql.QueryStatementGenerator;
import org.dbwiki.data.query.xaql.XAQLQuery;
import org.dbwiki.data.query.xaql.XAQLSyntaxParser;
import org.dbwiki.data.query.xaql.XAQLToken;
import org.dbwiki.data.query.xpath.AbsoluteXPathConsumer;
import org.dbwiki.data.time.TimeSequence;
import org.dbwiki.exception.WikiException;
import org.dbwiki.exception.data.WikiQueryException;
import org.parboiled.Parboiled;
import org.parboiled.buffers.DefaultInputBuffer;
import org.parboiled.errors.ErrorUtils;
import org.parboiled.parserunners.ReportingParseRunner;
import org.parboiled.support.ParsingResult;
public class XAQLQueryStatement extends QueryStatement {
/*
* Private Variables
*/
private Database _database;
private XAQLQuery _query;
/*
* Constructors
*/
public XAQLQueryStatement(Database database, String queryExpression) throws org.dbwiki.exception.WikiException {
_database = database;
XAQLSyntaxParser parser = Parboiled.createParser(XAQLSyntaxParser.class);
ParsingResult<XAQLToken> result = new ReportingParseRunner<XAQLToken>(parser.QueryStatement()).run(new DefaultInputBuffer(queryExpression.toCharArray()));
if (result.hasErrors()) {
throw new WikiQueryException(WikiQueryException.InvalidWikiQuery, queryExpression + "\n" + ErrorUtils.printParseErrors(result));
} else {
//result.parseTreeRoot.getValue().print("", "\t");
_query = new QueryStatementGenerator().getStatement(database, result.parseTreeRoot.getValue());
}
}
/**
* Evaluates the query against the database and returns a QueryResultSet
*
* @throws org.dbwiki.exception.WikiException
*/
public QueryResultSet execute() throws WikiException {
QueryResultSet result = null;
if (_query.getVersionClause() != null) {
result = new QueryResultSet(_query.getVersionClause().getTimestamp());
} else {
result = new QueryResultSet();
}
QueryNodeHandler queryHandler = _query.getQueryHandler(result);
// Collect all the entries that potentially match the query condition. For each of the
// candidate entries we then evaluate the query statement and add the results to the
// QueryResultSet.
DatabaseContent content = _database.getMatchingEntries(_query.getConditionListing());
for (int iEntry = 0; iEntry < content.size(); iEntry++) {
DatabaseGroupNode entry = (DatabaseGroupNode)_database.get(content.get(iEntry).identifier());
if (_query.getVersionClause() != null) {
entry = this.versionReader(entry, _query.getVersionClause().getTimestamp());
if (entry != null) {
new AbsoluteXPathConsumer().consume(entry, _query.rootTargetPath(), queryHandler);
}
} else { // This is dead code because version clause defaults to NOW.
// Could handle "interpret missing version as NOW" here.
new AbsoluteXPathConsumer().consume(entry, _query.rootTargetPath(), queryHandler);
}
}
return result;
}
/*
* Private Methods
*/
private void filterChildrenByTimestamp(DatabaseAttributeNode node, TimeSequence timestamp) {
int iChild = 0;
while (iChild < node.value().size()) {
DatabaseTextNode child = node.value().get(iChild);
if (child.hasTimestamp()) {
if (!child.getTimestamp().intersect(timestamp).isEmpty()) {
iChild++;
} else {
node.value().remove(iChild);
}
} else {
iChild++;
}
}
}
private void filterChildrenByTimestamp(DatabaseGroupNode node, TimeSequence timestamp) {
int iChild = 0;
while (iChild < node.children().size()) {
DatabaseElementNode child = node.children().get(iChild);
if (!child.getTimestamp().intersect(timestamp).isEmpty()) {
if (child.isAttribute()) {
this.filterChildrenByTimestamp((DatabaseAttributeNode)child, timestamp);
} else {
this.filterChildrenByTimestamp((DatabaseGroupNode)child, timestamp);
}
iChild++;
} else {
node.children().remove(iChild);
}
}
}
private DatabaseGroupNode versionReader(DatabaseGroupNode entry, TimeSequence timestamp) {
if (!entry.getTimestamp().intersect(timestamp).isEmpty()) {
this.filterChildrenByTimestamp(entry, timestamp);
return entry;
} else {
return null;
}
}
}