I would like to retrieve the following information:
select names from database where names like 'Jon';
but for MongoDB in Java. Essentially, it should return all names that contain the word Jon in them, like Jonathan, Jong etc etc. I know that there is the $in operator in MongoDB, but how do I do the same in Java, using the Java driver? I've been trying to look for it everywhere but am getting nothing. I've tried: query = new BasicDBObject("names", new BasicDBObject("$in", "Jon"));, and query = new BasicDBObject("names", new BasicDBObject("$in", Jon));
But neither of them worked :( Please help!
The MongoDB Java driver equivalent of that SELECT statement would be:
BasicDBObject fields = new BasicDBObject().append("name", 1); // SELECT name
BasicDBObject query = new BasicDBObject().append("name", "Jon"); // WHERE name = "Jon"
DBCursor results = yourCollection.find(query, fields); // FROM yourCollection
When you want to search for a part of a string, you can use the $regex operator:
query = new BasicDBObject("name", new BasicDBObject("$regex", "Jon"));
This will get you all objects where the name matches the regular expression Jon, which is everything which includes the string "Jon" anywhere.
Check the Mongo-Java official site, plus a nice library for mapping mongo objects
The $in operator in MongoDB resembles the IN operator in SQL. For instance, it can be used for executing SQL-like queries as
SELECT * FROM table WHERE id IN {1, 4, 6, 7, 9}
This is why it doesn't work for you. Use Regular expressions, as the others have already suggested.
Related
What I am trying to accomplish here is pretty simple. I am trying to update a single document in MongoDB collection. When I look up the document using any field, such as "name", the update query succeeds. Here is the query:
mongoDB.getCollection("restaurants").updateOne(
new BasicDBObject("name", "Morris Park Bake Shop"),
new BasicDBObject("$set", new BasicDBObject("zipcode", "10462"))
);
If I try to lookup the document with the ObjectId, it never works as it doesn't match any document.
mongoDB.getCollection("restaurants").updateOne(
new BasicDBObject("_id", "56110fe1f882142d842b2a63"),
new BasicDBObject("$set", new BasicDBObject("zipcode", "10462"))
);
Is it possible to make this query work with Object IDs?
I agree that my question is a bit similar to How to query documents using "_id" field in Java mongodb driver? however I am not getting any errors while trying to update a document. It just doesn't match anything.
You're currently trying to update based on a string, not an ObjectId.
Make sure to initialise a new ObjectId from the string when building your query:
mongoDB.getCollection("restaurants").updateOne(
new BasicDBObject("_id", new ObjectId("56110fe1f882142d842b2a63")),
new BasicDBObject("$set", new BasicDBObject("zipcode", "10462"))
);
#sheilak's answer is the best one but,
You could use {"_id", {"$oid","56110fe1f882142d842b2a63"}} as the filter for the update query if you want it to be in the string format
Convert the string to objectid:
from bson.objectid import ObjectId
db.collection.find_one({"_id":ObjectId('5a61bfadef860e4bf266edb2')})
{u'_id': ObjectId('5a61bfadef860e4bf266edb2'), ...
How do I create a new Query instance having the property of not matching any document, analogous to the MatchAllDocsQuery, but opposite?
A Boolean query without any clause returns no documents.
Query blank = new BooleanQuery();
For newer versions of Lucene you can use the Builder with the same result.
Query blank = new BooleanQuery.Builder().build();
I'm relatively new to MongoDB and I'm currently working with java towards a "find by most tags matching" solution to information within a collection.
I'm stuck now trying to translate a MongoDB shell operation to the JAVA driver version (this sintaxis is part of the definitions needed )
$cond:[{$eq: ["$tags", 200]}, 1, 0]
What would be a correct JAVA implementation for the sentence above?
Thank you in advance
Whatever the $cond object where in your aggregation operation, to build it to should do something like this:
BasicDBList eqList = new BasicDBList();
eqList.add("$tags");
eqList.add(200);
DBObject eqObject = BasicDBObjectBuilder.start()
.add("$eq", eqList)
.get();
BasicDBList condList = new BasicDBList();
condList.add(eqObject);
condList.add(1);
condList.add(0);
DBObject condObject = BasicDBObjectBuilder.start()
.add("$cond", condList)
.get();
I'm confusing about your aggregation operation, could you give more details?
I'm learning the Hibernate Search Query DSL, and I'm not sure how to construct queries using boolean arguments such as AND or OR.
For example, let's say that I want to return all person records that have a firstName value of "bill" or "bob".
Following the hibernate docs, one example uses the bool() method w/ two subqueries, such as:
QueryBuilder b = fts.getSearchFactory().buildQueryBuilder().forEntity(Person.class).get();
Query luceneQuery = b.bool()
.should(b.keyword().onField("firstName").matching("bill").createQuery())
.should(b.keyword().onField("firstName").matching("bob").createQuery())
.createQuery();
logger.debug("query 1:{}", luceneQuery.toString());
This ultimately produces the lucene query that I want, but is this the proper way to use boolean logic with hibernate search? Is "should()" the equivalent of "OR" (similarly, does "must()" correspond to "AND")?.
Also, writing a query this way feels cumbersome. For example, what if I had a collection of firstNames to match against? Is this type of query a good match for the DSL in the first place?
Yes your example is correct. The boolean operators are called should instead of OR because of the names they have in the Lucene API and documentation, and because it is more appropriate: it is not only influencing a boolean decision, but it also affects scoring of the result.
For example if you search for cars "of brand Fiat" OR "blue", the cars branded Fiat AND blue will also be returned and having an higher score than those which are blue but not Fiat.
It might feel cumbersome because it's programmatic and provides many detailed options. A simpler alternative is to use a simple string for your query and use the QueryParser to create the query. Generally the parser is useful to parse user input, the programmatic one is easier to deal with well defined fields; for example if you have the collection you mentioned it's easy to build it in a for loop.
You can also use BooleanQuery. I would prefer this beacuse You can use this in loop of a list.
org.hibernate.search.FullTextQuery hibque = null;
org.apache.lucene.search.BooleanQuery bquery = new BooleanQuery();
QueryBuilder qb = fulltextsession.getSearchFactory().buildQueryBuilder()
.forEntity(entity.getClass()).get();
for (String keyword : list) {
bquery.add(qb.keyword().wildcard().onField(entityColumn).matching(keyword)
.createQuery() , BooleanClause.Occur.SHOULD);
}
if (!filterColumn.equals("") && !filterValue.equals("")) {
bquery.add(qb.keyword().wildcard().onField(column).matching(value).createQuery()
, BooleanClause.Occur.MUST);
}
hibque = fulltextsession.createFullTextQuery(bquery, entity.getClass());
int num = hibque.getResultSize();
To answer you secondary question:
For example, what if I had a collection of firstNames to match against?
I'm not an expert, but according to (the third example from the end of) 5.1.2.1. Keyword queries in Hibernate Search Documentation, you should be able to build the query like so:
Collection<String> namesCollection = getNames(); // Contains "billy" and "bob", for example
StringBuilder names = new StringBuilder(100);
for(String name : namesCollection) {
names.append(name).append(" "); // Never mind the space at the end of the resulting string.
}
QueryBuilder b = fts.getSearchFactory().buildQueryBuilder().forEntity(Person.class).get();
Query luceneQuery = b.bool()
.should(
// Searches for multiple possible values in the same field
b.keyword().onField("firstName").matching( sb.toString() ).createQuery()
)
.must(b.keyword().onField("lastName").matching("thornton").createQuery())
.createQuery();
and, have as a result, Persons with (firstName preferably "billy" or "bob") AND (lastName = "thornton"), although I don't think it will give the good ol' Billy Bob Thornton a higher score ;-).
I was looking for the same issue and have a somewhat different issue than presented. I was looking for an actual OR junction. The should case didn't work for me, as results that didn't pass any of the two expressions, but with a lower score. I wanted to completely omit these results. You can however create an actual boolean OR expression, using a separate boolean expression for which you disable scoring:
val booleanQuery = cb.bool();
val packSizeSubQuery = cb.bool();
packSizes.stream().map(packSize -> cb.phrase()
.onField(LUCENE_FIELD_PACK_SIZES)
.sentence(packSize.name())
.createQuery())
.forEach(packSizeSubQuery::should);
booleanQuery.must(packSizeSubQuery.createQuery()).disableScoring();
fullTextEntityManager.createFullTextQuery(booleanQuery.createQuery(), Product.class)
return persistenceQuery.getResultList();
Title asks it all... I want to do a multi field - phrase search in Lucene.. How to do it ?
for example :
I have fields as String s[] = {"title","author","content"};
I want to search harry potter across all fields.. How do I do it ?
Can someone please provide an example snippet ?
Use MultiFieldQueryParser, its a QueryParser which constructs queries to search multiple fields..
Other way is to use Create a BooleanQuery consisting of TermQurey (in your case phrase query).
Third way is to include the content of other fields into your default content field.
Add
Generally speaking, querying on multiple fields isn’t the best practice for user-entered queries. More commonly, all words you want searched are indexed into a contents or keywords field by combining various fields.
Update
Usage:
Query query = MultiFieldQueryParser.parse(Version.LUCENE_30, new String[] {"harry potter","harry potter","harry potter"}, new String[] {"title","author","content"},new SimpleAnalyzer());
IndexSearcher searcher = new IndexSearcher(...);
Hits hits = searcher.search(query);
The MultiFieldQueryParser will resolve the query in this way: (See javadoc)
Parses a query which searches on the
fields specified. If x fields are
specified, this effectively
constructs:
(field1:query1) (field2:query2)
(field3:query3)...(fieldx:queryx)
Hope this helps.
intensified googling revealed this :
http://lucene.472066.n3.nabble.com/Phrase-query-on-multiple-fields-td2292312.html.
Since it is latest and best, I'll go with his approach I guess.. Nevertheless, it might help someone who is looking for something like I am...
You need to use MultiFieldQueryParser with escaped string. I have tested it with Lucene 8.8.1 and it's working like magic.
String queryStr = "harry potter";
queryStr = "\"" + queryStr.trim() + "\"";
Query query = new MultiFieldQueryParser(new String[]{"title","author","content"}, new StandardAnalyzer()).parse(queryStr);
System.out.println(query);
It will print.
(title:"harry potter") (author:"harry potter") (content:"harry potter")