Find entries via substring regex query in mongodb-go-driver

Question

I can't get the official go mongo driver to successfully return objects that are queried via a regex query.

I already know how to do it via the mongo shell and get my expected results. With this example i get all entries that contain "he" in their 'text' field:

db.getCollection('test').find({"text": /he/})

same with this one:

db.getCollection('test').find({"text": {$regex: /he/, $options: ''}})

This is my current code that doesn't work:

package main

import (
    "context"
    "fmt"
    "time"

    "go.mongodb.org/mongo-driver/bson"
    "go.mongodb.org/mongo-driver/bson/primitive"
    "go.mongodb.org/mongo-driver/mongo"
    "go.mongodb.org/mongo-driver/mongo/options"
)

func main() {
    ctx, cancel := context.WithTimeout(context.Background(), time.Duration(5*time.Second))
    defer cancel()
    client, err := mongo.NewClient(options.Client().ApplyURI("mongodb://localhost:27017"))
    if err != nil {
        fmt.Println(err)
        return
    }
    err = client.Connect(ctx)
    if err != nil {
        fmt.Println(err)
        return
    }
    db := client.Database("test")
    coll := db.Collection("test")

    filter := bson.D{{"text", primitive.Regex{Pattern: "/he/", Options: ""}}}
    ctx, cancel = context.WithTimeout(context.Background(), 5*time.Second)
    defer cancel()

    cur, err := coll.Find(ctx, filter)
    if err != nil {
        fmt.Println(err)
        return
    }

    i := 0
    for cur.Next(ctx) {
        i = i + 1
    }
    fmt.Println("Found", i, "elements")
}

Per example in the official mongo-go-driver repository, this should work.

My current entries in the collection just contain 2 fields, the id field and an extra text field. I currently have 3 entries. that look like this:

{
    "_id" : ObjectId("5c9cc7e9950198ceeefecbdd"),
    "text" : "hello world"
},
{
    "_id" : ObjectId("5c9cc7f6950198ceeefecbec"),
    "text" : "hello"
},
{
    "_id" : ObjectId("5c9cc804950198ceeefecbfa"),
    "text" : "test world"
}

My expected results with the code from above, should be the first 2 entries. Instead i get an empty cursor back.

Does anybode know, what i am doing wrong? Thanks for your help.

Answer 1

primitive.Regex struct accepts Pattern value without slashes, so it must be:

filter := bson.D{{"text", primitive.Regex{Pattern: "he", Options: ""}}}