regex - How to find all documents having an identical values in two fields with MongoDB? - 


given new documents , querys: {     "_id" : objectid("55803fd1cc0c9aa090e608be"),     "song_name" : "mickey good",     "time" : "3.56",     "artist" : "mickey" }   {     "_id" : objectid("55803fd1cc0c9aa090e608bf"),     "song_name" : "love nothing",     "time" : "5.56",     "artist" : "jimmy" }

i need find songs have title identical artist name. have tried: db.mycollection.find( { $where: "this.artist == /this.song_name/" } );

but did not work out. please help`

if understand well, need find songs title contains name of artist. don't need regular expression that1. simple test using indexof suffice. given sample data:

> db.test.find({$where:       "this.song_name.tolowercase().indexof(this.artist.tolowercase()) > -1" })  { "_id" : objectid("557ccec684ee2ba0375f4fcf"),   "song_name" : "mickey good",   "time" : "3.56",   "artist" : "mickey" }

if need find songs title is equal artist name (you don't have such document in sample data), write:

> db.test.find({$where:       "this.song_name.tolowercase() == this.artist.tolowercase()" })  { "_id" : objectid("557cd12284ee2ba0375f4fd1"),   "song_name" : "the monkeys",   "artist" : "the monkeys" }

please note in either cases, i've normalized strings using tolowercase(). depending use case, might need more sophisticated that. example, if need match "you , me" "you+me".

1using regular expression here might harmful if artist name contains meta-characters or quantifiers. example, given artist name "you+me", + here interpreted 1 or more occurrence of preceding character. so, matching "youme", "youuuuume" but not raw string "you+me".


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