Question 115948 in Mongodb Question posted in
The official documentation can be found here.

How to create a text index in MongoDb using MongoDb driver if it is not exist

Note: other answers are for older versions.

version : 2.18

I am using MongoDb.Driver with C# and want to create an Index only if it does not exist.
There is no method to check the existence of an Index and I can not create Index either. All the answers and docs are very old :

protected readonly IMongoDatabase _database;

protected readonly IMongoCollection<Product> _collection;

public ProductConfiguration(IMongoDatabase mongoDatabase)
{
    _database = mongoDatabase;
    _collection = _database.GetCollection<Product>(typeof(Product).Name);
}

public void CreateProductIndex()
{
    _collection.Indexes // no method to check the existence of an Index
}
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3

Answers


  1. 0 
    // no method to check the existence of an Index

    that’s not true, there is a method List that shows indexes for the current collection.

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  2. 0

    You don’t need to check if index is already created or not. If index is already created then database will ignore your new index creation request.

    _collection.Indexes.CreateOne("{ title : 1 }");

    You can still check the details of the index by following code:

    var indexList = _collection.Indexes.List().ToList< BsonDocument>();

indexList.ForEach(ix => Console.WriteLine(ix));`
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  3. 0

    I created an extension method for IMongoCollection to check, wether an index for a given name already exists in that collection:

    public static bool HasIndex<T>(this IMongoCollection<T> mongoCollection, string indexName)
{
    var indexes = mongoCollection.Indexes.List().ToList();
    var indexNames = indexes
        .SelectMany(i => i.Elements)
        .Where(e => string.Equals(e.Name, "name", StringComparison.CurrentCultureIgnoreCase))
        .Select(n => n.Value.ToString()).ToList();

    return indexNames.Contains(indexName);
}

    So whenever you want to check if an index exists in a specific collection of a mongo database you can check it via this example:

    var database = _mongoClient.GetDatabase("Database");
var examples = database.GetCollection<Example>("Examples");

var hasIndex = examples.HasIndex("ExampleIndex");
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