MongoDB writing a query for search engine - regex

Question

I am trying to write a search script in MongoDB but can't figure out how to do it....The thing I wan't to do is as follows....
Lets I have a string array XD = {"the","new","world"}
Now i want to search string array XD in MongoDB document (using regex) and get the result document. For example..
{ _id: 1, _content: "there was a boy" }
{ _id: 2, _content: "there was a boy in a new world" }
{ _id: 3, _content: "a boy" }
{ _id: 4, _content: "there was a boy in world" }
now I want to get result in accordance to _content contains the string in string array XD
{ _id: 2, _content: "there was a boy in a new world", _times: 3 }
{ _id: 4, _content: "there was a boy in world", times: 2 }
{ _id: 1, _content: "there was a boy", times: 1 }
as first document (_id : 2 ) contains all three { "the" in there, "new" as new, "world" as world } so it got 3
second document (_id: 4) only two { "world" as world } so it got 2

Answer 1

Here is what you can do.
Create a Regex to be matched with _content
XD = ["the","new","world"];
regex = new RegExp(XD.join("|"), "g");
Store a JS function on the server, which matches the _content with XD and returns the counts matched
db.system.js.save(
{
_id: "findMatchCount",
value : function(str, regexStr) {
XD = ["the","new","world"];
var matches = str.match(regexStr);
return (matches !== null) ? matches.length : 0;
}
}
)
Use the function with mapReduce
db.test.mapReduce(
function(regex) {
emit(this._id, findMatchCount(this._content, regex));
},
function(key,values) {
return values;
},
{ "out": { "inline": 0 } }
);
This will produce the output as below:
{
"results" : [
{
"_id" : 1,
"value" : 1
},
{
"_id" : 2,
"value" : 1
},
{
"_id" : 3,
"value" : 1
},
{
"_id" : 4,
"value" : 1
}
],
"timeMillis" : 1,
"counts" : {
"input" : 4,
"emit" : 4,
"reduce" : 0,
"output" : 4
},
"ok" : 1
}
I am not sure how efficient this solution is but it works.
Hope this helps.