creating a compound index in c#

Question

I want to create a compound index where one key should be in ascending, the second key in descending order.

How can I do this?

I have a string containing the property names the user selected.

collection.EnsureIndex(IndexKeys.Descending(selectedProperties[0]),
                IndexKeys.Ascending(selectedProperties[1])),
IndexOptions.......

does not work

score 14 · Answer 1 · answered Oct 02 '16 at 16:46

14

In v2.x of the driver they completely changed the API so currently the way to create a compound index asynchronously (which is prefered) is:

await collection.Indexes.CreateOneAsync(
    Builders<Hamster>.IndexKeys.Ascending(_ => _.Name).Descending(_ => _.Age),
    new CreateIndexOptions { Background = true });

And synchronously:

collection.Indexes.CreateOne(
    Builders<Hamster>.IndexKeys.Ascending(_ => _.Name).Descending(_ => _.Age),
    new CreateIndexOptions { Sparse = true });

answered Oct 02 '16 at 16:46

i3arnon

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1

How to create more than one indexes in v2.3 ( Indexes.CreateMany())? – Sri Chatala May 09 '17 at 21:20
what exactly the "Background=true" option does here? – Venkatesh Dharavath Jan 15 '21 at 17:15

score 11 · Answer 2 · answered Feb 16 '13 at 01:09

11

Here's one way:

var keys = new IndexKeysBuilder();

keys.Ascending(keyName1);
keys.Descending(keyName2);

var options = new IndexOptionsBuilder();
options.SetSparse(true);
options.SetUnique(false);
collection.EnsureIndex(keys, options);

answered Feb 16 '13 at 01:09

WiredPrairie

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score 6 · Answer 3 · answered Jul 12 '14 at 14:07

EnsureIndex is now obsolete, so CreateIndex should be used instead. There are also static builder classes the support fluent usage: IndexKeys and IndexOptions.

So the cleanest option is:

collection.CreateIndex(
    IndexKeys.Ascending(keyName1).Descending(keyName2),
    IndexOptions.SetSparse(true).SetUnique(false));

And for a generic type-safe option:

collection.CreateIndex(
    IndexKeys<Document>.Ascending(d => d.Property1).Descending(d => d.Property2),
    IndexOptions.SetSparse(true).SetUnique(false));

score -1 · Answer 4 · edited Jul 29 '20 at 01:41

-1

CreateIndex with

var indexModel = new CreateIndexModel<T>(keys.Ascending(x => x.Property1).Ascending(x=>x.Property2));
                
collection.Indexes.CreateOne(indexModel);

edited Jul 29 '20 at 01:41

Sasha Kondrashov

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answered Jul 28 '20 at 21:37

aadreja

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thank you for your answer, aadreja. could you please add some text to explain why this is the best answer, or how it works? – Sasha Kondrashov Jul 29 '20 at 00:03
@SashaKondrashov - collection.CreateIndex with index keys is obsolete (http://mongodb.github.io/mongo-csharp-driver/2.9/apidocs/html/M_MongoDB_Driver_IMongoIndexManager_1_CreateOne_2.htm). – aadreja Jul 29 '20 at 11:12

creating a compound index in c#

4 Answers4