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[DL-Learner SVN] SF.net SVN: dl-learner:[2113] trunk
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From: <jen...@us...> - 2010-03-11 16:09:45
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Revision: 2113
http://dl-learner.svn.sourceforge.net/dl-learner/?rev=2113&view=rev
Author: jenslehmann
Date: 2010-03-11 15:12:28 +0000 (Thu, 11 Mar 2010)
Log Message:
-----------
implemented extraction database cache using embedded H2 database
Modified Paths:
--------------
trunk/src/dl-learner/org/dllearner/kb/sparql/Cache.java
Added Paths:
-----------
trunk/lib/db/h2-1.2.131.jar
trunk/src/dl-learner/org/dllearner/kb/sparql/ExtractionDBCache.java
Added: trunk/lib/db/h2-1.2.131.jar
===================================================================
(Binary files differ)
Property changes on: trunk/lib/db/h2-1.2.131.jar
___________________________________________________________________
Added: svn:mime-type
+ application/octet-stream
Modified: trunk/src/dl-learner/org/dllearner/kb/sparql/Cache.java
===================================================================
--- trunk/src/dl-learner/org/dllearner/kb/sparql/Cache.java 2010-03-10 20:12:38 UTC (rev 2112)
+++ trunk/src/dl-learner/org/dllearner/kb/sparql/Cache.java 2010-03-11 15:12:28 UTC (rev 2113)
@@ -137,6 +137,7 @@
// compute md5-hash
private String getHash(String string) {
+ Monitor hashTime = JamonMonitorLogger.getTimeMonitor(Cache.class, "HashTime").start();
// calculate md5 hash of the string (code is somewhat
// difficult to read, but there doesn't seem to be a
// single function call in Java for md5 hashing)
@@ -154,7 +155,9 @@
for (int i = 0; i < result.length; i++) {
hexString.append(Integer.toHexString(0xFF & result[i]));
}
- return hexString.toString();
+ String str = hexString.toString();
+ hashTime.stop();
+ return str;
}
// return filename where the query result should be saved
Added: trunk/src/dl-learner/org/dllearner/kb/sparql/ExtractionDBCache.java
===================================================================
--- trunk/src/dl-learner/org/dllearner/kb/sparql/ExtractionDBCache.java (rev 0)
+++ trunk/src/dl-learner/org/dllearner/kb/sparql/ExtractionDBCache.java 2010-03-11 15:12:28 UTC (rev 2113)
@@ -0,0 +1,151 @@
+/**
+ * Copyright (C) 2007-2010, Jens Lehmann
+ *
+ * This file is part of DL-Learner.
+ *
+ * DL-Learner 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.
+ *
+ * DL-Learner 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 this program. If not, see <http://www.gnu.org/licenses/>.
+ *
+ */
+package org.dllearner.kb.sparql;
+
+import java.io.ByteArrayOutputStream;
+import java.io.StringReader;
+import java.io.UnsupportedEncodingException;
+import java.security.MessageDigest;
+import java.security.NoSuchAlgorithmException;
+import java.sql.Clob;
+import java.sql.Connection;
+import java.sql.DriverManager;
+import java.sql.PreparedStatement;
+import java.sql.ResultSet;
+import java.sql.SQLException;
+import java.sql.Statement;
+
+import org.dllearner.utilities.Helper;
+
+import com.hp.hpl.jena.rdf.model.Model;
+import com.hp.hpl.jena.rdf.model.ModelFactory;
+import com.hp.hpl.jena.sparql.engine.http.QueryEngineHTTP;
+
+/**
+ * The class is used to cache information about resources to a database.
+ * Provides the connection to an H2 database in a light weight, configuration free
+ * manner.
+ *
+ * @author Jens Lehmann
+ *
+ */
+public class ExtractionDBCache {
+
+ private String databaseDirectory = "cache";
+ private String databaseName = "extraction";
+
+ // specifies after how many seconds a cached result becomes invalid
+ private long freshnessSeconds = 15 * 24 * 60 * 60; // 15 days
+
+ private Connection conn;
+
+ MessageDigest md5;
+
+ public ExtractionDBCache() throws ClassNotFoundException, SQLException, NoSuchAlgorithmException {
+ md5 = MessageDigest.getInstance("MD5");
+
+ // load driver
+ Class.forName("org.h2.Driver");
+
+ // connect to database (created automatically if not existing)
+ conn = DriverManager.getConnection("jdbc:h2:"+databaseDirectory+"/"+databaseName, "sa", "");
+
+ // create cache table if it does not exist
+ Statement stmt = conn.createStatement();
+ stmt.execute("CREATE TABLE IF NOT EXISTS QUERY_CACHE(QUERYHASH BINARY PRIMARY KEY,QUERY VARCHAR(255), TRIPLES CLOB, STORE_TIME TIMESTAMP)");
+ }
+
+ public Model executeConstructQuery(String query) throws SQLException, UnsupportedEncodingException {
+ byte[] md5 = md5(query);
+// Timestamp currTS = new Timestamp(new java.util.Date().getTime());
+ PreparedStatement ps=conn.prepareStatement("SELECT * FROM QUERY_CACHE WHERE QUERYHASH=? LIMIT 1");
+ ps.setBytes(1, md5);
+ ResultSet rs = ps.executeQuery();
+
+ boolean readFromCache = rs.next() && (rs.getTimestamp("STORE_TIME").getTime() - System.currentTimeMillis() < freshnessSeconds);
+
+ if(readFromCache) {
+// System.out.println("Reading from cache");
+// String posedQuery = rs.getString("QUERY");
+// System.out.println(posedQuery);
+ Clob clob = rs.getClob("TRIPLES");
+ Model readModel = ModelFactory.createDefaultModel();
+ readModel.read(clob.getAsciiStream(), null, "N-TRIPLE");
+ return readModel;
+ } else {
+// System.out.println("Posing new query");
+
+ String endpoint = "http://139.18.2.37:8890/sparql";
+ QueryEngineHTTP queryExecution = new QueryEngineHTTP(endpoint, query);
+ queryExecution.addDefaultGraph("http://dbpedia.org");
+ Model m2 = queryExecution.execConstruct();
+
+ // convert model to N-Triples
+ ByteArrayOutputStream baos = new ByteArrayOutputStream();
+ m2.write(baos, "N-TRIPLE");
+ String modelStr = baos.toString("UTF-8");
+
+ // use a prepared statement, so that Java handles all the escaping stuff correctly automatically
+ PreparedStatement ps2=conn.prepareStatement("INSERT INTO QUERY_CACHE VALUES(?,?,?,?)");
+ ps2.setBytes(1, md5);
+ ps2.setString(2, query);
+ ps2.setClob(3, new StringReader(modelStr));
+ ps2.setTimestamp(4, new java.sql.Timestamp(new java.util.Date().getTime()));
+ ps2.executeUpdate();
+
+ return m2;
+ }
+ }
+
+ public void closeConnection() throws SQLException {
+ conn.close();
+ }
+
+ private byte[] md5(String string) {
+ md5.reset();
+ md5.update(string.getBytes());
+ return md5.digest();
+ }
+
+ public static String toNTriple(Model m) {
+ ByteArrayOutputStream baos = new ByteArrayOutputStream();
+ m.write(baos, "N-TRIPLE");
+ try {
+ return baos.toString("UTF-8");
+ } catch (UnsupportedEncodingException e) {
+ e.printStackTrace();
+ return null;
+ }
+ }
+
+ public static void main(String[] args) throws ClassNotFoundException, SQLException, NoSuchAlgorithmException, UnsupportedEncodingException {
+ String resource = "http://dbpedia.org/resource/Leipzig";
+ String query = "CONSTRUCT { <"+resource+"> ?p ?o } WHERE { <"+resource+"> ?p ?o }";
+ System.out.println("query: " + query);
+
+ ExtractionDBCache h2 = new ExtractionDBCache();
+ long startTime = System.nanoTime();
+ Model m = h2.executeConstructQuery(query);
+ long runTime = System.nanoTime() - startTime;
+ System.out.println("Answer obtained in " + Helper.prettyPrintNanoSeconds(runTime));
+ System.out.println(ExtractionDBCache.toNTriple(m));
+ }
+
+}
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