I serialized a BooleanQuery constructed using TermQuery's into a string. Now I am trying to de-serialize the string back into a BooleanQuery on a different node in a distributed system. So while de-serializing, I have multiple fields and I do not want to use an analyzer
Eg : I am trying to parse the below string without analyzing
+contents:maxItemsPerBlock +path:/lucene-5.1.0/core/src/java/org/apache/lucene/codecs/blocktree/Stats.java
QueryParser in lucene requires an analyzer, but I want the above field values to be treated as terms. I am looking for a query parser which does something like the below since I do not want to parse the strings and construct the query myself.
TermQuery q1 = new TermQuery(new Term("contents", "maxItemsPerBlock"));
TermQuery q2 = new TermQuery(new Term("path", "/lucene-5.1.0/core/src/java/org/apache/lucene/codecs/blocktree/Stats.java"));
BooleanQuery q = new BooleanQuery();
q.add(q1, BooleanClause.Occur.MUST);
q.add(q2, BooleanClause.Occur.MUST);
Also when I tried using a whitespace analyzer with a QueryParser, I got an "IllegalArgumentException : field must not be null" error. Below is the sample code
Analyzer analyzer = new WhitespaceAnalyzer();
String field = "contents";
QueryParser parser = new QueryParser(null, analyzer);
Query query = parser.parse("+contents:maxItemsPerBlock +path:/home/rchallapalli/Desktop/lucene-5.1.0/core/src/java/org/apache/lucene/codecs/blocktree/Stats.java");
java.lang.IllegalArgumentException: field must not be null
at org.apache.lucene.search.MultiTermQuery.<init>(MultiTermQuery.java:233)
at org.apache.lucene.search.AutomatonQuery.<init>(AutomatonQuery.java:99)
at org.apache.lucene.search.AutomatonQuery.<init>(AutomatonQuery.java:81)
at org.apache.lucene.search.RegexpQuery.<init>(RegexpQuery.java:108)
at org.apache.lucene.search.RegexpQuery.<init>(RegexpQuery.java:93)
at org.apache.lucene.queryparser.classic.QueryParserBase.newRegexpQuery(QueryParserBase.java:572)
at org.apache.lucene.queryparser.classic.QueryParserBase.getRegexpQuery(QueryParserBase.java:774)
at org.apache.lucene.queryparser.classic.QueryParserBase.handleBareTokenQuery(QueryParserBase.java:844)
at org.apache.lucene.queryparser.classic.QueryParser.Term(QueryParser.java:348)
at org.apache.lucene.queryparser.classic.QueryParser.Clause(QueryParser.java:247)
at org.apache.lucene.queryparser.classic.QueryParser.Query(QueryParser.java:202)
at org.apache.lucene.queryparser.classic.QueryParser.TopLevelQuery(QueryParser.java:160)
at org.apache.lucene.queryparser.classic.QueryParserBase.parse(QueryParserBase.java:117)
Considering the text you offer in your question. Maybe WhitespaceAnalyzer which splits tokens at whitespace is a choice.
Before you serialize the BooleanQuery constructed by TermQuery, the term in TermQuery is actually what you want to match in the Lucene Index.
// code in Scala
val parser = new QueryParser(version, "", new WhitespaceAnalyzer((version)))
val parsedQuery = parser.parse(searchString)
I tried the following two cases: single-value field and multi-valued field, all work.
+contents:maxItemsPerBlock +path:/lucene-5.1.0/core/src/java/org/apache/lucene/codecs/blocktree/Stats.java
+(contents:maxItemsPerBlock contents:minItemsPerBlock) +path:/lucene-5.1.0/core/src/java/org/apache/lucene/codecs/blocktree/Stats.java
Besides, in our system the serialization and deserialization when it comes to Query passing between nodes are based on
java's ObjectInputStream and ObjectOutputStream. So you may try in that way so you don't have to consider the Analyzer thing.
Related
There are two queries,one is created by QueryParser:
QueryParser parser = new QueryParser(field, analyzer);
Query query1 = parser.parse("Lucene");
the other is term query:
Query query2=new TermQuery(new Term("title", "Lucene"));
what is the difference between query1 and query2?
This is the definition of Term from lucene docs.
A Term represents a word from text. This is the unit of search. It is composed of two elements, the text of the word, as a string, and the name of the field that the text occurred in.
So in your case the query will be created to search the word "Lucene" in the field "title".
To explain the difference between the two let me take a difference example,
consider the following
Query query2 = new TermQuery(new Term("title", "Apache Lucene"));
In this case the query will search for the exact word "Apache Lucene" in the field title.
In the other case
As an example, let's assume a Lucene index contains two fields, "title" and "body".
QueryParser parser = new QueryParser("title", "StandardAnalyzer");
Query query1 = parser.parse("title:Apache body:Lucene");
Query query2 = parser.parse("title:Apache Lucene");
Query query3 = parser.parse("title:\"Apache Lucene\"");
couple of things.
"title" is the field that QueryParser will search if you don't prefix it with a field.(as given in the constructor).
parser.parse("title:Apache body:Lucene"); -> in this case the final query will look like this. query2 = title:Apache body:Lucene.
parser.parse("body:Apache Lucene"); -> in this case the final query will also look like this. query2 = body:Apache title:Lucene. but for a different reason.
So the parser will search "Apache" in body field and "Lucene" in title field. Since The field is only valid for the term that it directly precedes,(http://lucene.apache.org/core/2_9_4/queryparsersyntax.html)
So since we do not specify any field for lucene , the default field which is "title" will be used.
query2 = parser.parse("title:\"Apache Lucene\""); in this case we are explicitly telling that we want to search for "Apache Lucene" in field "title". This is phrase query and is similar to Term query if analyzed correctly.
So to summarize the term query will not analyze the term and search as it is. while Query parser parses the input based on some conditions described above.
The QueryParser parses the string and constructs a BooleanQuery (afaik) consisting of BooleanClauses and analyzes the terms along the way.
The TermQuery does NOT do analysis, and takes the term as-is. This is the main difference.
So the query1 and query2 might be equivalent (in a sense, that they provide the same search results) if the field is the same, and the QueryParser's analyzer is not changing the term.
How do I get search hit like below mentioned scenario using lucene search?
Example:
Hi Hello world
In above example, if I enter "Hello wo",or "Hel",or "Hello" I need to get a hit.
that means if entered phrase or character exits in search string I need to get hit
Here is my code to get hits:
QueryParser parser = null;
Query query = null;
Analyzer analyzer = new StandardAnalyzer(Version.LUCENE_CURRENT, new HashSet());
BooleanQuery.setMaxClauseCount(32767);
parser = new QueryParser("fieldname", analyzer);
parser.setAllowLeadingWildcard(true);
query = parser.parse("searchString");
TopDocs topResultDocs = searcher.search(query, null, 20);
The simplest way, would just be to create a prefix query by adding a wildcard (*) to the end of the search string, like:
query = parser.parse("hel*")
Alternatively, you might also use an ngram filter in your analyzer to split tokens into smaller chunks.
I have the following issue using Lucene.NET 3.0.3.
My project analyze Documents using StandardAnalyzer with StopWord-List (combined german and english words).
While searching I create my searchterm by hand and parse it using MultiFieldQueryParser. The Parser is initialized with the same analyzer as indexing documents.
The parsed search query initialized a BooleanQuery. The BooleanQuery and a TopScoreDocCollector search in the Lucene index with IndexSearcher.
My code looks like:
using (StandardAnalyzer analyzer = new StandardAnalyzer(Lucene.Net.Util.Version.LUCENE_30, roxConnectionTools.getServiceInstance<ISearchIndexService>().GetStopWordList()))
{
...
MultiFieldQueryParser parser = new MultiFieldQueryParser(Lucene.Net.Util.Version.LUCENE_30, searchFields, analyzer);
parser.MultiTermRewriteMethod = MultiTermQuery.SCORING_BOOLEAN_QUERY_REWRITE;
parser.AllowLeadingWildcard = true;
...
Query searchQuery = parser.Parse(searchStringBuilder.ToString().Trim);
...
BooleanQuery boolQuery = new BooleanQuery();
boolQuery.Add(searchQuery, Occur.MUST);
...
TopScoreDocCollector scoreCollector = TopScoreDocCollector.Create(SearchServiceTools.MAX_SCORE_COLLECTOR_SIZE, true);
...
searcher.Search(boolQuery, scoreCollector);
ScoreDoc[] scoreDocs = scoreCollector.TopDocs().ScoreDocs;
}
If I index a document field with value "Test- und Produktivumgebung" I can´t find this document by searching this term.
I get results if I correct the search term to "Test- Produktivumgebung".
The word "und" is in my StopWord-List.
My search query looks like the following:
Manually generated search query: (+*Test* +*und* +*Produktivumgebung*)
Parsed search query: +(title:*Test*) +(title:*und*) +(title:*Produktivumgebung*)
Why I can´t find the document searching for "Test- und Produktivumgebung"?
Wildcard Queries are not analyzed (See this question, for an example). Since you are (if I understand correctly), interpreting the query "Test- und Produktivumgebung" to (+*Test* +*und* +*Produktivumgebung*), the analyzer is not used for any of those wildcard queries, and stop words will not be eliminated.
If you eliminate the step that performs that translation, the query "Test- und Produktivumgebung" should be parsed to a phrase query and analyzed, and should work just fine. Another reason to eliminate that step, is that applying a leading wildcard to every term will cause your performance to become very poor. That's why leading wildcards must be manually enabled, because it is generally a bad idea to use them.
Suppose I have a search using criteria such as a list countries. A user can select a set of countries to search across and combine this set with other criteria.
In SQL I'd do this in my where clause i.e. WHERE (country = 'brazil' OR country = 'france' OR country = 'china) AND (other search criteria).
It isn't clear how to do this in Lucene. Query.combine seems to have promise but that would increase in complexity very quickly if I have multiple sets of "OR" terms to work through.
Is Lucene capable in this regard? Or should I just hit my regular DB with these types of criteria and filter my Lucene results?
Digging deeper, it looks like you can nest boolean queries to accomplish this. I'll update with an answer if this technique works and if it is performant.
Using the standard query parser(and you can take a look at the relevant documentation), you can use syntax similar to a DB query, such as:
(country:brazil OR country:france OR country:china) AND (other search criteria)
Or, to simplify a bit:
country:(brazil OR france OR china) AND (other search criteria)
Alternatively, Lucene also supports queries written using +/-, rather than AND/OR syntax. I find that syntax more expressive for a Lucene query. The equivalent in this form would be:
+country:(brazil france china) +(other search criteria)
If manually constructing queries, you can indeed nest BooleanQueries to create a similar structure, using the correct BooleanClauses to establish the And/Or logic you've specified:
Query countryQuery = new BooleanQuery();
countryQuery.add(new TermQuery(new Term("country","brazil")),BooleanClause.Occur.SHOULD);
countryQuery.add(new TermQuery(new Term("country","france")),BooleanClause.Occur.SHOULD);
countryQuery.add(new TermQuery(new Term("country","china")),BooleanClause.Occur.SHOULD);
Query otherStuffQuery = //Set up the other query here,
//or get it from a query parser, or something
Query rootQuery = new BooleanQuery();
rootQuery.add(countryQuery, BooleanClause.Occur.MUST);
rootQuery.add(otherStuffQuery, BooleanClause.Occur.MUST);
Two ways.
Let the Lucene formulate the query. To accomplish that, send in the query string in the following format.
Query: "country(brazil france china)"
An inbuilt QueryParser parses the above string to a BooleanQuery with an OR operator.
QueryParser qp = new QueryParser(Version.LUCENE_41, "country", new StandardAnalyzer(Version.LUCENE_41));
Query q = qp.parse(s);
If you want to formulate the query yourself,
BooleanQuery bq = new BooleanQuery();
//
TermQuery tq = new TermQuery(new Term("country", "brazil"));
bq.add(tq, Occur.SHOULD); // SHOULD ==> OR operator
//
tq = new TermQuery(new Term("country", "france"));
bq.add(tq, Occur.SHOULD);
//
tq = new TermQuery(new Term("country", "china"));
bq.add(tq, Occur.SHOULD);
Unless you add hundreds of subqueries, Lucene will meet your expectations performance-wise.
I've got an index where I need to get all documents with a standard search, still ranked by relevance, even if a document isn't a hit.
My first idea is to add a field that is always matched, but that might deform the relevance score.
Use a BooleanQuery to combine your original query with a MatchAllDocsQuery. You can mitigate the effect this has on scoring by setting the boost on the MatchAllDocsQuery to zero before you combine it with your main query. This way you don't have to add an otherwise bogus field to the index.
For example:
// Parse a query by the user.
QueryParser qp = new QueryParser(Version.LUCENE_35, "text", new StandardAnalyzer());
Query standardQuery = qp.parse("User query may go here");
// Make a query that matches everything, but has no boost.
MatchAllDocsQuery matchAllDocsQuery = new MatchAllDocsQuery();
matchAllDocsQuery.setBoost(0f);
// Combine the queries.
BooleanQuery boolQuery = new BooleanQuery();
boolQuery.add(standardQuery, BooleanClause.Occur.SHOULD);
boolQuery.add(matchAllDocsQuery, BooleanClause.Occur.SHOULD);
// Now just pass it to the searcher.
This should give you hits from standardQuery followed by the rest of the documents in the index.