CODEWITHSUNDEEP
regexmongodb
stenci
stenci

Reputation: 8481

Unexpected result in mongodb query with regular expression

The first query below shows the full content of the collection and the following three queries return one item as expected.

Why does the last query return two items?

> db.log.find()
{ "_id" : 123, "user" : "stefano" }
{ "_id" : 456, "user" : "franco" }
> db.log.find({'user':/st/})
{ "_id" : 123, "user" : "stefano" }
> db.log.find({'user':/fr/})
{ "_id" : 456, "user" : "franco" }
> db.log.find({'user':/st*/})
{ "_id" : 123, "user" : "stefano" }
> db.log.find({'user':/fr*/})
{ "_id" : 123, "user" : "stefano" }
{ "_id" : 456, "user" : "franco" }

Upvotes: 0

Views: 83

Answers (1)

mgyongyosi
mgyongyosi

Reputation: 2667

Because in Regex the * is a quantifier (matches between zero and unlimited times). So the /fr*/ regex matches f literally and a r zero or unlimited times. (https://regex101.com/r/M8h249/1)

If you would like to create a regex which matches like a "starts with" then you can use the following: /^fr/.

Upvotes: 2

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