This question might sound lame but I am really confused...This is my code for normal query :
public class test4query extends Object {
public static String[] arr=new String[30];
public void mai (String s) {
String directory = "EMAILADDRESS" ;
Dataset ds = TDBFactory.createDataset(directory) ;
ds.begin(ReadWrite.READ) ;
Model model = ds.getDefaultModel() ;
QueryExecution qExec = QueryExecutionFactory.create(s, ds) ;
int i=0;
try{
ResultSet rs = qExec.execSelect() ;
String x=rs.toString();
while (rs.hasNext()) {
QuerySolution qs = rs.next();
String rds;
if(qs.get("x")!=null) {
rds = qs.get("x").toString();
} else {
rds="hi";
}
if(rds==null) {
break;
}
System.out.println(rds);
arr[i] = rds;
i++;
}
} finally
{qExec.close() ;
ds.commit();
ds.end();
}
}
}
But this does not work for delete queries ..It shows error :
Was expecting one of:
"base" ...
"prefix" ...
"select" ...
"describe" ...
"construct" ...
"ask" ...
I know some changes need to be made for update queries?Can somebody give some hint?Any link will be helpful!!
SPARQL Query and SPARQL Update are different languages, and there are different factories for parsing them. QueryFactory is for the SPARQL 1.1 Query Language. For the SPARQL 1.1 Update, you need to use UpdateFactory.
Related
I am using the highlighting feature of Lucene to isolate matching terms for my query, but some of the matched terms are excessive.
I have some simple test cases which are delivered in an Ant project (download details below).
Materials
You can download the test case here: mydemo_with_libs.zip
That archive includes the Lucene 8.6.3 libraries which my test uses; if you prefer a copy without the JAR files you can download that from here: mydemo_without_libs.zip
The necessary libraries are: core, analyzers, queries, queryparser, highlighter, and memory.
You can run the test case by unzipping the archive into an empty directory and running the Ant command ant synsearch
Input
I have provided a short synonym list which is used for indexing and analysing in the highlighting methods:
cope,manage
jobs,tasks
simultaneously,at once
and there is one document being indexed:
Queues are a useful way of grouping jobs together in order to manage a number of them at once. You can:
hold or release multiple jobs at the same time;
group multiple tasks (for the same event);
control the priority of jobs in the queue;
Eventually log all events that take place in a queue.
Use either job.queue or task.queue in specifications.
Process
When building the index I am storing the text field, and using a custom analyzer. This is because (in the real world) the content I am indexing is technical documentation, so stripping out punctuation is inappropriate because so much of it may be significant in technical expressions. My analyzer uses a TechTokenFilter which breaks the stream up into tokens consisting of strings of words or digits, or individual characters which don't match the previous pattern.
Here's the relevant code for the analyzer:
public class MyAnalyzer extends Analyzer {
public MyAnalyzer(String synlist) {
if (synlist != "") {
this.synlist = synlist;
this.useSynonyms = true;
}
}
public MyAnalyzer() {
this.useSynonyms = false;
}
#Override
protected TokenStreamComponents createComponents(String fieldName) {
WhitespaceTokenizer src = new WhitespaceTokenizer();
TokenStream result = new TechTokenFilter(new LowerCaseFilter(src));
if (useSynonyms) {
result = new SynonymGraphFilter(result, getSynonyms(synlist), Boolean.TRUE);
result = new FlattenGraphFilter(result);
}
return new TokenStreamComponents(src, result);
}
and here's my filter:
public class TechTokenFilter extends TokenFilter {
private final CharTermAttribute termAttr;
private final PositionIncrementAttribute posIncAttr;
private final ArrayList<String> termStack;
private AttributeSource.State current;
private final TypeAttribute typeAttr;
public TechTokenFilter(TokenStream tokenStream) {
super(tokenStream);
termStack = new ArrayList<>();
termAttr = addAttribute(CharTermAttribute.class);
posIncAttr = addAttribute(PositionIncrementAttribute.class);
typeAttr = addAttribute(TypeAttribute.class);
}
#Override
public boolean incrementToken() throws IOException {
if (this.termStack.isEmpty() && input.incrementToken()) {
final String currentTerm = termAttr.toString();
final int bufferLen = termAttr.length();
if (bufferLen > 0) {
if (termStack.isEmpty()) {
termStack.addAll(Arrays.asList(techTokens(currentTerm)));
current = captureState();
}
}
}
if (!this.termStack.isEmpty()) {
String part = termStack.remove(0);
restoreState(current);
termAttr.setEmpty().append(part);
posIncAttr.setPositionIncrement(1);
return true;
} else {
return false;
}
}
public static String[] techTokens(String t) {
List<String> tokenlist = new ArrayList<String>();
String[] tokens;
StringBuilder next = new StringBuilder();
String token;
char minus = '-';
char underscore = '_';
char c, prec, subc;
// Boolean inWord = false;
for (int i = 0; i < t.length(); i++) {
prec = i > 0 ? t.charAt(i - 1) : 0;
c = t.charAt(i);
subc = i < (t.length() - 1) ? t.charAt(i + 1) : 0;
if (Character.isLetterOrDigit(c) || c == underscore) {
next.append(c);
// inWord = true;
}
else if (c == minus && Character.isLetterOrDigit(prec) && Character.isLetterOrDigit(subc)) {
next.append(c);
} else {
if (next.length() > 0) {
token = next.toString();
tokenlist.add(token);
next.setLength(0);
}
if (Character.isWhitespace(c)) {
// shouldn't be possible because the input stream has been tokenized on
// whitespace
} else {
tokenlist.add(String.valueOf(c));
}
// inWord = false;
}
}
if (next.length() > 0) {
token = next.toString();
tokenlist.add(token);
// next.setLength(0);
}
tokens = tokenlist.toArray(new String[0]);
return tokens;
}
}
Examining the index I can see that the index contains the separate terms I expect, including the synonym values. For example the text at the end of the first line has produced the terms
of
them
at , simultaneously
once
.
You
can
:
and the text at the end of the third line has produced the terms
same
event
)
;
When the application performs a search it analyzes the query without using the synonym list (because the synonyms are already in the index), but I have discovered that I need to include the synonym list when analyzing the stored text to identify the matching fragments.
Searches match the correct documents, but the code I have added to identify the matching terms over-performs. I won't show all the search method here, but will focus on the code which lists matched terms:
public static void doSearch(IndexReader reader, IndexSearcher searcher,
Query query, int max, String synList) throws IOException {
SimpleHTMLFormatter htmlFormatter = new SimpleHTMLFormatter("\001", "\002");
Highlighter highlighter = new Highlighter(htmlFormatter, new QueryScorer(query));
Analyzer analyzer;
if (synList != null) {
analyzer = new MyAnalyzer(synList);
} else {
analyzer = new MyAnalyzer();
}
// Collect all the docs
TopDocs results = searcher.search(query, max);
ScoreDoc[] hits = results.scoreDocs;
int numTotalHits = Math.toIntExact(results.totalHits.value);
System.out.println("\nQuery: " + query.toString());
System.out.println("Matches: " + numTotalHits);
// Collect matching terms
HashSet<String> matchedWords = new HashSet<String>();
int start = 0;
int end = Math.min(numTotalHits, max);
for (int i = start; i < end; i++) {
int id = hits[i].doc;
float score = hits[i].score;
Document doc = searcher.doc(id);
String docpath = doc.get("path");
String doctext = doc.get("text");
try {
TokenStream tokens = TokenSources.getTokenStream("text", null, doctext, analyzer, -1);
TextFragment[] frag = highlighter.getBestTextFragments(tokens, doctext, false, 100);
for (int j = 0; j < frag.length; j++) {
if ((frag[j] != null) && (frag[j].getScore() > 0)) {
String match = frag[j].toString();
addMatchedWord(matchedWords, match);
}
}
} catch (InvalidTokenOffsetsException e) {
System.err.println(e.getMessage());
}
System.out.println("matched file: " + docpath);
}
if (matchedWords.size() > 0) {
System.out.println("matched terms:");
for (String word : matchedWords) {
System.out.println(word);
}
}
}
Problem
While the correct documents are selected by these queries, and the fragments chosen for highlighting do contain the query terms, the highlighted pieces in some of the selected fragments extend over too much of the input.
For example, if the query is
+text:event +text:manage
(the first example in the test case) then I would expect to see 'event' and 'manage' in the highlighted list. But what I actually see is
event);
manage
Despite the highlighting process using an analyzer which breaks terms apart and treats punctuation characters as single terms, the highlight code is "hungry" and breaks on whitespace alone.
Similarly if the query is
+text:queeu~1
(my final test case) I would expect to only see 'queue' in the list. But I get
queue.
job.queue
task.queue
queue;
It is so nearly there... but I don't understand why the highlighted pieces are inconsistent with the index, and I don't think I should have to parse the list of matches through yet another filter to produce the correct list of matches.
I would really appreciate any pointers to what I am doing wrong or how I could improve my code to deliver exactly what I need.
Thanks for reading this far!
I managed to get this working by replacing the WhitespaceTokenizer and TechTokenFilter in my analyzer with a PatternTokenizer; the regular expression took a bit of work but once I had it all the matching terms were extracted with pinpoint accuracy.
The replacement analyzer:
public class MyAnalyzer extends Analyzer {
public MyAnalyzer(String synlist) {
if (synlist != "") {
this.synlist = synlist;
this.useSynonyms = true;
}
}
public MyAnalyzer() {
this.useSynonyms = false;
}
private static final String tokenRegex = "(([\\w]+-)*[\\w]+)|[^\\w\\s]";
#Override
protected TokenStreamComponents createComponents(String fieldName) {
PatternTokenizer src = new PatternTokenizer(Pattern.compile(tokenRegex), 0);
TokenStream result = new LowerCaseFilter(src);
if (useSynonyms) {
result = new SynonymGraphFilter(result, getSynonyms(synlist), Boolean.TRUE);
result = new FlattenGraphFilter(result);
}
return new TokenStreamComponents(src, result);
}
I am trying to write propreties into a model and then query it.This part of mycode:
String directory = "EMAILADDRESS" ;
//create the dataset for the tdb store
Dataset ds = TDBFactory.createDataset(directory) ;
//create default rdf model
ds.begin(ReadWrite.WRITE);
Model model = ds.getDefaultModel() ;
//write to the tdb dataset
When I write this and then query the query shows no result ...but when I interchange the order of model and begin i.e.
Model model = ds.getDefaultModel() ;
//write to the tdb dataset
ds.begin(ReadWrite.WRITE);
Then it works fine!! but it sometimes gives this error:
com.hp.hpl.jena.tdb.transaction.TDBTransactionException: Not in a transaction
I know that first way is correct but I don't understand why it doesn't respond to queries..This is code for quering:
public class test4query extends Object {
public static String[] arr=new String[30];
public void mai (String s) {
String directory = "EMAILADDRESS" ;
Dataset ds = TDBFactory.createDataset(directory) ;
ds.begin(ReadWrite.READ) ;
Model model = ds.getDefaultModel() ;
QueryExecution qExec = QueryExecutionFactory.create(s, ds) ;
int i=0;
try{
ResultSet rs = qExec.execSelect() ;
String x=rs.toString();
while (rs.hasNext()) {
QuerySolution qs = rs.next();
String rds;
if(qs.get("x")!=null) {
rds = qs.get("x").toString();
} else {
rds="hi";
}
if(rds==null) {
break;
}
System.out.println(rds);
arr[i] = rds;
i++;
}
} finally
{qExec.close() ;
ds.commit();
ds.end();
}
}
}
It is unclear when you get hat exception. The code example is full of parts that are commented out and does not use "m" at all.
You can not call ResultSetFormatter.out(rs) after you have called qExec.close or ds.commit.
I am struggeling on how to use indexes in cypher.
After creating and indexing nodes in java
I am fine with executing cypher queries on those nodes.
I am fine as well with querying those nodes using the created index in java.
However, when I call the index in the cypher statement I get an MissingIndexException.
So, why can't cypher find the index? Do I have to create a separate cypher index? (I have not found anything about that)
I am using version 1.8.2
Here's what I did:
public class IndexTester {
String DB_PATH = "target/java-query-db";
String resultString ="";
GraphDatabaseService db = new GraphDatabaseFactory().newEmbeddedDatabase( DB_PATH );
ExecutionEngine engine = new ExecutionEngine( db );
IndexManager index = db.index();
Index<Node> personIndex;
Node n;
Node n1;
public static void main( String[] args )
{
IndexTester indexTester = new IndexTester();
indexTester.runIndex();
}
public void runIndex(){
Transaction tx = db.beginTx();
try
{
personIndex = index.forNodes( "person" );
n = createAndIndexNode("type", "adult", personIndex, db);
addPropertyAndIndexNode("name", "John", personIndex, n);
addPropertyAndIndexNode("id", "1", personIndex, n);
n1 = createAndIndexNode("type", "adult", personIndex, db);
addPropertyAndIndexNode("name", "Jane", personIndex, n1);
addPropertyAndIndexNode("id", "2", personIndex, n1);
//This works fine!!
Node foundNode = personIndex.get("name", "John").getSingle();
System.out.println("Found Node: " + foundNode.getProperty("name"));
//This throws a MissingIndexException
resultString = engine.execute( "start m=node:personIndex(name= 'John') return m" ).toString();
System.out.println(resultString);
n.delete();
n1.delete();
tx.success();
}
finally
{
tx.finish();
}
}
private Node createAndIndexNode(final String property, final String name, Index<Node> nodeIndex, GraphDatabaseService db ) {
Node node = db.createNode();
node.setProperty(property , name);
nodeIndex.add(node, property, name);
return node;
}
public Node addPropertyAndIndexNode(String property, String name, Index<Node> nodeIndex, Node node)
{
node.setProperty( property, name );
nodeIndex.add( node, property, node.getProperty( property ) );
return node;
}
}
Any ideas / suggestions how to solve this?
Thank you!!
I think the actual name of your index is just person (as specified here: index.forNodes( "person" );), rather than personIndex.
Try:
start m=node:person(name= 'John') return m
I took a dummy language for example:
It simply accepts one or more '!'.
its lexer and grammar rules are:
grammar Ns;
options {
output=AST;
ASTLabelType=CommonTree;
}
tokens {
NOTS;
}
#header {
package test;
}
#lexer::header {
package test;
}
ns : NOT+ EOF -> ^(NOTS NOT+);
NOT : '!';
ok, as you can see, this represents a language which accept '!' or '!!!' or '!!!!!'...
and I defined some meaningful classes to build ASTs:
public class Not {
public static final Not SINGLETON = new Not();
private Not() {
}
}
public class Ns {
private List<Not> nots;
public Ns(String nots) {
this.nots = new ArrayList<Not>();
for (int i = 0; i < nots.length(); i++) {
this.nots.add(Not.SINGLETON);
}
}
public String toString() {
String ret = "";
for (int i = 0; i < this.nots.size(); i++) {
ret += "!";
}
return ret;
}
}
and here's the tree grammar:
tree grammar NsTreeWalker;
options {
output = AST;
tokenVocab = Ns;
ASTLabelType = CommonTree;
}
#header {
package test;
}
ns returns [Ns ret] : ^(NOTS n=NOT+) {$ret = new Ns($n.text);};
and the main class code with some sample data to test the generated classes:
public class Test {
public static void main(String[] args) throws Exception {
ANTLRInputStream input = new ANTLRInputStream(new ByteArrayInputStream("!!!".getBytes("utf-8")));
NsLexer lexer = new NsLexer(input);
CommonTokenStream tokens = new CommonTokenStream(lexer);
NsParser parser = new NsParser(tokens);
CommonTree root = (CommonTree) parser.ns().getTree();
NsTreeWalker walker = new NsTreeWalker(new CommonTreeNodeStream(root));
try {
NsTreeWalker.ns_return r = walker.ns();
System.out.println(r.ret);
} catch (RecognitionException e) {
e.printStackTrace();
}
}
}
but the final output printed is '!', other than the expecting '!!!'.
that's mainly because this line of code :
ns returns [Ns ret] : ^(NOTS n=NOT+) {$ret = new Ns($n.text);};
the $n above captured only one '!', I don't know how to capture all three tokens of '!', in other words , a list of '!' with $n.
Is there some one could help?thanks!
The fact that only one ! gets printed is because your rule:
ns returns [Ns ret]
: ^(NOTS n=NOT+) {$ret = new Ns($n.text);}
;
gets more or less translated as:
Token n = null
LOOP
n = match NOT_token
END
return new Ns(n.text)
Therefor, n.text will always be just a single !.
What you need to do is collect these NOT tokens in a list. In ANTLR you can create a list of tokens using the += operator instead of the "single token" operator =. So change your ns rule into:
ns returns [Ns ret]
: ^(NOTS n+=NOT+) {$ret = new Ns($n);}
;
which gets translated as:
List n = null
LOOP
n.add(match NOT_token)
END
return new Ns(n)
Be sure to change the constructor of your Ns class to take a List instead:
public Ns(List nots) {
this.nots = new ArrayList<Not>();
for (Object o : nots) {
this.nots.add(Not.SINGLETON);
}
}
after which the output of your test class would be:
!!!
Good luck!
I am interfacing with a PostgreSQL database with NHibernate.
Background
I made some simple tests...it seems it's taking 2 seconds to persist 300 records.
I have a Perl program with identical functionality, but issue direct SQL instead, takes only 70% of the time.
I am not sure if this is expected. I thought C#/NHibernate would be faster or at least on par.
Questions
One of my observation is that (with show_sql turned on), the NHibernate is issuing INSERTs a few hundreds times, instead of doing bulk INSERT that take cares of multiple rows. And note I am assigning the primary key myself, not using the "native" generator.
Is that expected? Is there anyway I could make it issue bulk INSERT statement instead? It seems to me that this could be one of the area I could speed up the performance.
As stachu found out correctly: NHibernate does not have *BatchingBatcher(Factory) for PostgreSQL(Npgsql)
As stachu askes: Did anybody managed to force Nhibarnate to do batch inserts to PostgreSQL
I wrote a Batcher that doesn't use any Npgsql batching stuff, but does manipulate the SQL String "oldschool style" (INSERT INTO [..] VALUES (...),(...), ...)
using System;
using System.Collections;
using System.Data;
using System.Diagnostics;
using System.Text;
using Npgsql;
namespace NHibernate.AdoNet
{
public class PostgresClientBatchingBatcherFactory : IBatcherFactory
{
public virtual IBatcher CreateBatcher(ConnectionManager connectionManager, IInterceptor interceptor)
{
return new PostgresClientBatchingBatcher(connectionManager, interceptor);
}
}
/// <summary>
/// Summary description for PostgresClientBatchingBatcher.
/// </summary>
public class PostgresClientBatchingBatcher : AbstractBatcher
{
private int batchSize;
private int countOfCommands = 0;
private int totalExpectedRowsAffected;
private StringBuilder sbBatchCommand;
private int m_ParameterCounter;
private IDbCommand currentBatch;
public PostgresClientBatchingBatcher(ConnectionManager connectionManager, IInterceptor interceptor)
: base(connectionManager, interceptor)
{
batchSize = Factory.Settings.AdoBatchSize;
}
private string NextParam()
{
return ":p" + m_ParameterCounter++;
}
public override void AddToBatch(IExpectation expectation)
{
if(expectation.CanBeBatched && !(CurrentCommand.CommandText.StartsWith("INSERT INTO") && CurrentCommand.CommandText.Contains("VALUES")))
{
//NonBatching behavior
IDbCommand cmd = CurrentCommand;
LogCommand(CurrentCommand);
int rowCount = ExecuteNonQuery(cmd);
expectation.VerifyOutcomeNonBatched(rowCount, cmd);
currentBatch = null;
return;
}
totalExpectedRowsAffected += expectation.ExpectedRowCount;
log.Info("Adding to batch");
int len = CurrentCommand.CommandText.Length;
int idx = CurrentCommand.CommandText.IndexOf("VALUES");
int endidx = idx + "VALUES".Length + 2;
if (currentBatch == null)
{
// begin new batch.
currentBatch = new NpgsqlCommand();
sbBatchCommand = new StringBuilder();
m_ParameterCounter = 0;
string preCommand = CurrentCommand.CommandText.Substring(0, endidx);
sbBatchCommand.Append(preCommand);
}
else
{
//only append Values
sbBatchCommand.Append(", (");
}
//append values from CurrentCommand to sbBatchCommand
string values = CurrentCommand.CommandText.Substring(endidx, len - endidx - 1);
//get all values
string[] split = values.Split(',');
ArrayList paramName = new ArrayList(split.Length);
for (int i = 0; i < split.Length; i++ )
{
if (i != 0)
sbBatchCommand.Append(", ");
string param = null;
if (split[i].StartsWith(":")) //first named parameter
{
param = NextParam();
paramName.Add(param);
}
else if(split[i].StartsWith(" :")) //other named parameter
{
param = NextParam();
paramName.Add(param);
}
else if (split[i].StartsWith(" ")) //other fix parameter
{
param = split[i].Substring(1, split[i].Length-1);
}
else
{
param = split[i]; //first fix parameter
}
sbBatchCommand.Append(param);
}
sbBatchCommand.Append(")");
//rename & copy parameters from CurrentCommand to currentBatch
int iParam = 0;
foreach (NpgsqlParameter param in CurrentCommand.Parameters)
{
param.ParameterName = (string)paramName[iParam++];
NpgsqlParameter newParam = /*Clone()*/new NpgsqlParameter(param.ParameterName, param.NpgsqlDbType, param.Size, param.SourceColumn, param.Direction, param.IsNullable, param.Precision, param.Scale, param.SourceVersion, param.Value);
currentBatch.Parameters.Add(newParam);
}
countOfCommands++;
//check for flush
if (countOfCommands >= batchSize)
{
DoExecuteBatch(currentBatch);
}
}
protected override void DoExecuteBatch(IDbCommand ps)
{
if (currentBatch != null)
{
//Batch command now needs its terminator
sbBatchCommand.Append(";");
countOfCommands = 0;
log.Info("Executing batch");
CheckReaders();
//set prepared batchCommandText
string commandText = sbBatchCommand.ToString();
currentBatch.CommandText = commandText;
LogCommand(currentBatch);
Prepare(currentBatch);
int rowsAffected = 0;
try
{
rowsAffected = currentBatch.ExecuteNonQuery();
}
catch (Exception e)
{
if(Debugger.IsAttached)
Debugger.Break();
throw;
}
Expectations.VerifyOutcomeBatched(totalExpectedRowsAffected, rowsAffected);
totalExpectedRowsAffected = 0;
currentBatch = null;
sbBatchCommand = null;
m_ParameterCounter = 0;
}
}
protected override int CountOfStatementsInCurrentBatch
{
get { return countOfCommands; }
}
public override int BatchSize
{
get { return batchSize; }
set { batchSize = value; }
}
}
}
I also found that NHibernate is not doing batch inserts into PostgreSQL.
I identified two possible reasons:
1) Npgsql driver does not support batch inserts/updates (see forum)
2) NHibernate does not have *BatchingBatcher(Factory) for PostgreSQL(Npgsql). I tried using Devart dotConnect driver with NHibernate (I wrote custom driver for NHibernate) but it still did not worked.
I suppose this driver should also implement IEmbeddedBatcherFactoryProvider interface, but it seems not trivial for me (using one for Oracle did not worked ;) )
Did anybody managed to force Nhibarnate to do batch inserts to PostgreSQL or can confirm my conclusion?