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dfd1e745480fabd88139d2804acb90d5b6dc055e
secondo/OptServer/82/OptimizerServer.java

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firs commit
2026-01-23 17:03:45 +08:00
//This file is part of SECONDO.
//Copyright (C) 2021, University in Hagen, Department of Computer Science,
//Database Systems for New Applications.
//SECONDO 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 2 of the License, or
//(at your option) any later version.
//SECONDO 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 SECONDO; if not, write to the Free Software
//Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
import java.io.*;
import java.net.*;
import java.util.*;
import org.jpl7.*;
import java.nio.charset.Charset;
import java.util.SortedMap;
public class OptimizerServer extends Thread{
static {
System.loadLibrary( "jpl" );
System.loadLibrary( "regSecondo" );
}
public static native int registerSecondo();
/** shows a prompt at the console
*/
private static void showPrompt(){
cout.print("\n opt-server > ");
}
/** init prolog
* register the secondo predicate
* loads the optimizer prolog code
*/
private boolean initialize(){
// later here is to invoke the init function which
// registers the Secondo(command,Result) predicate to prolog
if(registerSecondo()!=0){
System.err.println("error in registering the secondo predicate ");
return false;
}
//cout.println("registerSecondo successful");
try{
String[] plargs = {"--stack-limit=256M"};
boolean ok = JPL.init(plargs);
// VTA - 18.09.2006
// I added this piece of code in order to run with newer versions
// of prolog. Without this code, the libraries (e.g. lists.pl) are
// not automatically loaded. It seems that something in our code
// (auxiliary.pl and calloptimizer.pl) prevents them to be
// automatically loaded. In order to solve this problem I added
// a call to 'member(x, [x]).' so that the libraries are loaded
// before running our scripts.
Term[] args = new Term[2];
args[0] = new Atom("x");
args[1] = org.jpl7.Util.termArrayToList( new Term[] { new Atom("x") } );
Query q = new Query("member",args);
if(!q.hasSolution()){
cout.println("error in the member call'");
return false;
}
args = new Term[1];
args[0] = new Atom("auxiliary");
q = new Query("consult",args);
if(!q.hasSolution()){
cout.println("error in loading 'auxiliary.pl'");
return false;
}
args = new Term[1];
args[0] = new Atom("calloptimizer");
q = new Query("consult",args);
if(!q.hasSolution()){
cout.println("error in loading 'calloptimizer.pl'");
return false;
}
return true;
} catch(Exception e){
cout.println("Exception in initialization "+e);
e.printStackTrace();
return false;
}
}
public static boolean halt(){
try{
Query q = new Query("halt");
boolean res = command(q,null);
return res;
} catch(Exception e){
System.err.println(" error in shutting down the prolog engine");
e.printStackTrace();
return false;
}
}
/** invokes a prolog predicate
* all terms in variables must be contained in arguments
* variables and results can be null if no result is desired
*/
synchronized private static boolean command(Query pl_query, Vector results){
if(pl_query==null)
return false;
try{
if(trace){
cout.println("execute query: "+pl_query);
}
String ret ="";
int number =0; // the number of solutions
if(results!=null)
results.clear();
while(pl_query.hasMoreSolutions()){
number++;
Map<String, Term> solution = pl_query.nextSolution();
if(results!=null){
ret = "";
if(solution.size()<=0){
results.add("yes");
} else{
Set<String> vars = solution.keySet();
Iterator<String> it = vars.iterator();
int varnum =0;
while(it.hasNext()){
String k = it.next();
if (varnum>0) ret += " $$$ ";
ret += ( k + " = " + solution.get(k));
varnum++;
}
results.add(ret);
}
}
}
if(number == 0){
if(trace)
cout.println("no solution found for' "+pl_query.goal() +"/"+pl_query.goal().arity());
return false;
} else{
// check if the used database is changed
Query dbQuery = new Query("databaseName(X)");
if(dbQuery.hasMoreSolutions()){
Map<String, Term> sol = dbQuery.nextSolution();
String v = sol.keySet().iterator().next();
String name = ""+sol.get(v);
if(!name.equals(openedDatabase)){
if(trace){
cout.println("use database "+ name);
}
openedDatabase=name;
}
} else{ // no database open
openedDatabase = "";
}
return true;
}
} catch(Exception e){
if(trace){
cout.println("exception in calling the "+pl_query.goal()+"-predicate"+e);
e.printStackTrace();
}
return false;
}
}
/** analyzed the given string and extract the command and the argumentlist
* <br> then the given command is executed
* all Solutions are stored into the Vector Solution
*/
private synchronized static boolean execute(String command,Vector Solution){
if(Solution!=null)
Solution.clear();
// clients should not have the possibility
// to shut down the Optimizer-Server
command = command.trim();
if(command.startsWith("halt ") || command.equals("halt"))
return false;
Vector TMPVars = new Vector();
if(trace){
cout.println("analyse command: "+command);
}
command = encode(command);
try{
Query pl_query = new Query(command);
if(pl_query==null){
if(trace)
cout.println("error in parsing command: "+command);
return false;
}
boolean res = command(pl_query,Solution);
if(res & trace & Solution!=null){ // successful
if(Solution.size()==0)
cout.println("Yes");
else
for(int i=0;i<Solution.size();i++){
cout.println("*** Solution "+(i+1)+" ****");
cout.println(Solution.get(i));
}
}
return res;
} catch(Exception e){
if(trace){
cout.println("Exception occured " + e);
e.printStackTrace();
}
return false;
}
}
/** return the optimized query
* if no optimization is found, query is returned
* otherwise the result will be the best query plan
*/
private synchronized String optimize(String query){
//cout.println("optimize called with argument \""+query+"\"");
try{
if(trace){
cout.println("\n optimization-input : "+query+"\n");
}
// switch off check for number of linebreaks
Query lb_query = new Query("style_check(-atom)");
while(lb_query.hasMoreSolutions()){
lb_query.nextSolution();
}
if(trace){
cout.println("style check switched off successfully");
}
String query2 = encode(query);
if(trace) {
System.out.println("encoded Query: " + query2);
if(query.equals(query2)){
cout.println("original query and encoded query are equal");
} else {
cout.println("encoded query and original one differ");
}
}
Query pl_query=null;
try{
query2 = query2.replaceAll("'","\\\\'");
pl_query = new Query("sqlToPlan('"+query2+"', X )");
} catch(Exception e){
if(trace){
cout.println("Could not translate query");
cout.println(e);
}
return "";
}
if(trace){
System.out.println("text could be translated into a query");
}
String ret1 = "";
String allret = "";
int number =0;
while(pl_query.hasMoreSolutions()){
number++;
if(number > 1){
allret += "\n";
}
Map<String,Term> solution = pl_query.nextSolution();
if(solution.size()!=1){
if(trace){
cout.println("Error: optimization returns more than a single binding");
}
return query;
}
Iterator<String> it = solution.keySet().iterator();
while(it.hasNext()){
allret += "" + solution.get(it.next());
}
if(number==1){
ret1 = allret;
}
}
if(number>1){
if(trace){
cout.println("Error: optimization returns more than one solution");
cout.println("Solutions are \n" + allret);
}
ret1 = ret1.trim();
if(ret1.startsWith("'") && ret1.endsWith("'")){
if(ret1.length()==2){
ret1 = "";
} else{
ret1 = ret1.substring(1,ret1.length()-1);
}
}
return decode(ret1);
}
if(number==0){
if(trace)
cout.println("optimization failed - no solution found");
return query;
}
else{
if(trace)
cout.println("\n optimization-result : "+allret+"\n");
// free ret from enclosing ''
allret = allret.trim();
if(allret.startsWith("'") && allret.endsWith("'")){
if(allret.length()==2){
allret = "";
} else{
allret = allret.substring(1,allret.length()-1);
}
}
return decode(allret);
}
} catch(Exception e){
if(trace) {
cout.println("\n Exception :"+e);
e.printStackTrace();
}
showPrompt();
return query;
}
}
/** if Name is not the database currenty used,
* the opened database is closed and the database
* Name is opened
*/
private synchronized boolean useDatabase(String Name){
if(openedDatabase.equals(Name)){
return true;
}
Term[] arg = new Term[1];
if(!openedDatabase.equals("")){
if(trace)
cout.println("close the opened database");
Query Q = new Query("secondo('close database')");
command(Q,null);
}
Query Q_open = new Query("secondo('open database "+Name+"')");
showPrompt();
boolean res = command(Q_open,null);
openedDatabase = res?Name:"";
return res;
}
/** a class for communicate with a client */
private class Server extends Thread{
/** creates a new Server from given socket */
public Server(Socket S){
this.S = S;
//cout.println("requesting from client");
try{
// communication with client, always use UTF-8 encoding
try{
in = new BufferedReader(new InputStreamReader(S.getInputStream(),"UTF-8"));
} catch(UnsupportedEncodingException e){
System.err.println("Encoding UTF-8 not supported");
in = new BufferedReader(new InputStreamReader(S.getInputStream()));
}
try{
out = new BufferedWriter(new OutputStreamWriter(S.getOutputStream(),"UTF-8"));
} catch(UnsupportedEncodingException e){
System.err.println("Encoding UTF-8 not supported");
out = new BufferedWriter(new OutputStreamWriter(S.getOutputStream()));
}
String First = in.readLine();
//cout.println("receive :"+First);
if(First==null){
if(trace)
cout.println("connection broken");
showPrompt();
running=false;
return;
}
if(First.equals("<who>")){
out.write("<optimizer>\n",0,12);
out.flush();
running = true;
}else{
if(trace)
cout.println("protocol-error , close connection (expect: <who>, received :"+First);
showPrompt();
running = false;
}
}catch(Exception e){
if(trace){
cout.println("Exception occured "+e);
e.printStackTrace();
}
showPrompt();
running = false;
}
}
/** disconnect this server from a client */
private void disconnect(){
// close Connection if possible
try{
if(S!=null)
S.close();
}catch(Exception e){
if(trace){
cout.println("Exception in closing connection "+e);
e.printStackTrace();
}
}
OptimizerServer.Clients--;
if(trace){
cout.println("\nbye client");
cout.println("number of clients is :"+ OptimizerServer.Clients);
}
if((OptimizerServer.Clients==0) && OptimizerServer.quitAfterDisconnect){
// OptimizerServer.halt(); // not allowed from this tread
System.exit(0);
}
showPrompt();
}
/** processes requests from clients until the client
* finish the connection or an error occurs
*/
public void run(){
if(!running){
disconnect();
return;
}
boolean execFlag=false; // flags for control execute or optimize request
try{
String input = in.readLine();
if(input==null){
if(trace)
cout.println("connection is broken");
disconnect();
return;
}
while(!input.equals("<end connection>")){
if(!input.equals("<optimize>") && !input.equals("<execute>") ){ // protocol_error
if(trace)
cout.println("protocol error( expect: <optimize> or <execute> , found:"+input);
disconnect();
return;
}
//cout.println("receive "+input+" from client");
execFlag = input.equals("<execute>");
// read the database name
input = in.readLine();
//cout.println("receive "+input+" from client");
if(input==null){
if(trace)
cout.println("connection is broken");
disconnect();
return;
}
if(!input.equals("<database>")){ // protocol_error
if(trace)
cout.println("protocol error( expect: <database> , found:"+input);
disconnect();
return;
}
String Database = in.readLine();
//cout.println("receive "+Database+" from client");
if(Database==null){
cout.println("connection is broken");
disconnect();
return;
}else {
Database = Database.trim();
}
input = in.readLine();
//cout.println("receive "+input+" from client");
if(input==null){
if(trace)
cout.println("connection is broken");
disconnect();
return;
}else{
input = input.trim();
}
if(!input.equals("</database>")){ // protocol error
if(trace)
cout.println("protocol error( expect: </database> , found:"+input);
disconnect();
return;
}
input = in.readLine();
//cout.println("receive "+input+" from client");
if(input==null){
if(trace)
cout.println("connection is broken");
disconnect();
return;
}else{
input = input.trim();
}
if(!input.equals("<query>")){ // protocol error
if(trace)
cout.println("protocol error( expect: <query> , found:"+input);
disconnect();
return;
}
StringBuffer res = new StringBuffer();
// build the query from the next lines
input = in.readLine();
//cout.println("receive "+input+" from client");
//cout.println("receive"+input);
if(input==null){
if(trace)
cout.println("connection is broken");
disconnect();
return;
}
while(!input.equals("</query>")){
res.append(input + "\n");
input = in.readLine();
//cout.println("receive"+input);
if(input==null){
if(trace)
cout.println("connection is broken");
disconnect();
return;
}
}
input = in.readLine();
//cout.println("receive "+input+" from client");
if(input==null){
cout.println("connection is broken");
disconnect();
return;
}
if(! (input.equals("</optimize>") & !execFlag) & !(input.equals("</execute>") & execFlag)){ //protocol-error
if(trace)
cout.println("protocol error( expect: </optimize> or </execute>, found:"+input);
disconnect();
return;
}
String Request = res.toString().trim();
//cout.println("Request is " + Request );
Vector V = new Vector();
synchronized(SyncObj){
useDatabase(Database);
if(!execFlag){
String opt = OptimizerServer.this.optimize(Request);
if(!opt.equals(Request))
V.add(opt);
}else{
execute(Request,V);
}
}
showPrompt();
out.write("<answer>\n",0,9);
String answer;
for(int i=0;i<V.size();i++){
answer = (String) V.get(i);
out.write(answer+"\n",0,answer.length()+1);
}
out.write("</answer>\n",0,10);
out.flush();
input = in.readLine().trim();
//cout.println("receive "+input+" from client");
if (input==null){
cout.println("connection broken");
showPrompt();
disconnect();
return;
}
} // while
cout.println("connection ended normally");
showPrompt();
}catch(IOException e){
cout.println("error in socket-communication" + e);
disconnect();
showPrompt();
return;
}
disconnect();
}
private BufferedReader in;
private BufferedWriter out;
private boolean running;
private Socket S;
}
/** creates the server process */
private boolean createServer(){
SS=null;
try{
SS = new ServerSocket(PortNr);
} catch(java.net.BindException be){
cout.println("BindException occured");
cout.println("check if the port "+PortNr+" is already in use");
return false;
} catch(Exception e){
cout.println("unable to create a ServerSocket" + e);
e.printStackTrace();
return false;
}
return true;
}
/** waits for request from clients
* for each new client a new socket communicationis created
*/
public void run(){
cout.println("\nwaiting for requests");
showPrompt();
while(running){
try{
Socket S = SS.accept();
Clients++;
if(trace){
cout.println("\na new client is connected");
cout.println("number of clients :"+Clients);
showPrompt();
}
(new Server(S)).start();
} catch(Exception e){
cout.println("error in communication" + e);
showPrompt();
}
}
}
private static void showUsage(){
cout.println("java -classpath .:<jplclasses> OptimizerServer PORT [options] ");
cout.println("<jplclasses> : jar file containing the JPL (prolog) API");
cout.println("PORT : port for the server");
cout.println("[Options can be :");
cout.println(" -autoquit : exits the server if the last client disconnects");
cout.println(" -trace_methods : enables tracing of method calls (for debugging)");
cout.println(" -trace_instructions : enables tracing of instructions (for debugging)");
cout.println(" -trace_commands : enables tracing of input/output");
cout.println(" -encoding enc : switch the output encoding");
}
/** creates a new server object
* process inputs from the user
* available commands are
* client : prints out the number of connected clients
* quit : shuts down the server
*/
public static void main(String[] args){
cout = System.out;
if(args.length<1){
showUsage();
System.exit(1);
}
// process options
Runtime rt = Runtime.getRuntime();
int pos = 1;
String console_enc = "utf-8"; // standard
while(pos<args.length){
if(args[pos].equals("-autoquit")){
quitAfterDisconnect=true;
cout.println("auto quit enabled");
pos++;
} else if(args[pos].equals("-encoding")){
if(pos+1>=args.length){
showUsage();
System.exit(1);
}
console_enc = args[pos+1];
pos++;
pos++;
} else if(args[pos].equals("-trace_commands")){
trace=true;
pos++;
} else {
cout.println("unknown option " + args[pos]);
showUsage();
System.exit(1);
}
}
if(!console_enc.equals("utf-8")){
SortedMap available = Charset.availableCharsets();
if(!available.containsKey(console_enc)){
cout.println("encoding " + console_enc + " unknown");
cout.println(" Available encodinga are : ");
cout.println(available.keySet());
System.exit(1);
}
try {
cout = new PrintStream(System.out, true, console_enc);
} catch(Exception e){
cout = System.out;
cout.println("Problem in changing output encoding, use utf-8");
e.printStackTrace();
}
}
cout.println("\n\n");
printLicence(cout);
cout.println("\n");
String arg = args[0];
OptimizerServer OS = new OptimizerServer();
try{
int P = java.lang.Integer.parseInt(arg);
if(P<=0){
System.err.println("the Portnumber must be greater then zero");
System.exit(1);
}
OS.PortNr=P;
}catch(Exception e){
System.err.println("the Portnumber must be an integer");
System.exit(1);
}
try{
Class.forName("org.jpl7.fli.Prolog"); // ensure to load the jpl library
} catch(Exception e){
System.err.println("loading prolog class failed");
System.exit(1);
}
if(! OS.initialize()){
cout.println("initialization failed");
System.exit(1);
}
if(!OS.createServer()){
cout.println("creating Server failed");
System.exit(1);
}
OS.running = true;
OS.start();
try{
BufferedReader in = new BufferedReader(new InputStreamReader(System.in));
cout.print("optserver >");
String command = "";
Vector ResVector = new Vector();
while(!command.equals("quit")){
command = in.readLine();
if(command==null){
command = "";
continue;
}
command = command.trim();
if(command.equals("clients")){
cout.println("Number of Clients: "+ Clients);
}else if(command.equals("quit")){
if( Clients > 0){
cout.print("clients exists ! shutdown anyway (y/n) >");
String answer = in.readLine().trim().toLowerCase();
if(!answer.startsWith("y"))
command="";
}
} else if(command.equals("trace-on")){
trace=true;
cout.println("tracing is activated");
} else if(command.equals("trace-off")){
trace=false;
cout.println("tracing is deactivated");
} else if(command.equals("help") | command.equals("?") ){
cout.println("quit : quits the server ");
cout.println("clients : prints out the number of connected clients");
cout.println("trace-on : prints out messages about command, optimized command, open database");
cout.println("trace-off : disable messages");
} else if(command.startsWith("exec")){
String cmdline = command.substring(4,command.length()).trim();
execute(cmdline,ResVector);
}else if(!command.equals("")){
cout.println("unknow command, try help show a list of valid commands");
}
if(!command.equals("quit"))
showPrompt();
}
OS.running = false;
}catch(Exception e){
OS.running = false;
cout.println("error in reading commands");
if(trace)
e.printStackTrace();
}
try{
Query q = new Query("halt");
command(q,null);
} catch(Exception e){
System.err.println(" error in shutting down the prolog engine");
}
}
/** Prints out the licence information of this software **/
public static void printLicence(PrintStream out){
cout.println(" Copyright (C) 2021, University in Hagen, ");
cout.println(" Faculty of Mathematics and Computer Science, ");
cout.println(" Database Systems for New Applications. \n");
cout.println(" This is free software; see the source for copying conditions.");
cout.println(" There is NO warranty; not even for MERCHANTABILITY or FITNESS ");
cout.println(" FOR A PARTICULAR PURPOSE.");
}
/** Converts a string into OS_pl_encoding **/
private static String encode(String src){
if(OS_pl_encoding==null){
return src;
}
try{
byte[] encodedBytes = src.getBytes(OS_pl_encoding);
return new String(encodedBytes, "UTF-8");
} catch(Exception e){
System.err.println("Used encoding not supported\n" + e);
return src;
}
}
/** Converts a string from OS_pl_encoding **/
private static String decode(String src){
if(OS_pl_encoding==null){
return src;
}
try{
byte[] encodedBytes = src.getBytes("UTF-8");
return new String(encodedBytes, OS_pl_encoding);
} catch(Exception e){
System.err.println("Used encoding not supported\n" + e);
return src;
}
}
private static String OS_pl_encoding = null;
private boolean optimizer_loaded = false;
private int PortNr = 1235;
private static int Clients = 0;
private static boolean quitAfterDisconnect = false;
private ServerSocket SS;
private boolean running;
private static String openedDatabase ="";
private static boolean trace = true;
private static Object SyncObj = new Object();
private static PrintStream cout;
}
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