如何在不使用模式匹配的情况下使用Java API使用“喜欢”查询mongodb？

Question

Currently I am using java to connect to MONGODB, I want to write this sql query in mongodb using java driver:

select * from tableA where name like("%ab%")

is their any solution to perform the same task through java, the query in mongodb is very simple i know, the query is

db.collection.find({name:/ab/})

but how to perform same task in java

Current I am using pattern matching to perform the task and code is

DBObject A = QueryBuilder.start("name").is(Pattern.compile("ab", 
                                           Pattern.CASE_INSENSITIVE)).get();

but it makes query very slow I think , does a solution exist that does not use pattern matching?

Answer 1

Can use Regular Expressions. Take a look at the following:

http://www.mongodb.org/display/DOCS/Advanced+Queries#AdvancedQueries-RegularExpressions

Make sure you understand the potential performance impacts!

Answer 2

Why do you fear the regular expressions? Once the expression is compiled they are very fast, and if the expression is "ab" the result is similar to a function that search a substring in a string.

However to do what you need you have 2 possibilities:

1. The first one, using regular expression, as you mention in your question. And I believe this is the best solution .
2. The second one, using the $where queries .

With $where queries you can specify expression like these

db.foo.find({"$where" : "this.x + this.y == 10"})
db.foo.find({"$where" : "function() { return this.x + this.y == 10; }"})

and so you can use the JavaScript .indexOf() on string fields.

Answer 3

Code snippet using the $regex clause (as mentioned by mikeycgto )

String searchString = "ab";
DBCollection coll = db.getCollection("yourCollection");
query.put("name", 
  new BasicDBObject("$regex", String.format(".*((?i)%s).*", searchString)) );
DBCursor cur = coll.find(query);
while (cur.hasNext()) {
  DBObject dbObj = cur.next();
  // your code to read the DBObject ..       
}

As long as you are not opening and closing the connection per method call, the query should be fast.

Answer 4

DBObject A = QueryBuilder.start("name").is(Pattern.compile("ab", 
                                       Pattern.CASE_INSENSITIVE)).get();

I think this is one of the possible solution, you need to create index to achieve those.