TTL on timestamp fields are not accepted on older instances of Azure Cosmo DB for MongoDB

Kris Lemoine 25

We are using several Azure Cosmos DB for MongoDB (RU) instances running on server version 4.2.

We now want to create a TTL index on a timestamp field. When we create the index it gives the exception "The 'expireAfterSeconds' option is supported on '_ts' field only." We tried with updating the server to version 6.0, but still the same exception.

When we create a new instance, even in version 4.2, we are able to create the TTL index.

Our older instances don't allow the index on a timestamp field. Is there a way to update or enable this feature?

Oury Ba-MSFT 19,101 Reputation points Microsoft Employee

2024-07-23T02:02:42.3733333+00:00

@Kris Lemoine Thank you for reaching out.

Could you please try to create TTL using the command in this doc. The way indexes are created to be handled in any version should not be different.

https://learn.microsoft.com/en-us/azure/cosmos-db/mongodb/feature-support-32

https://learn.microsoft.com/en-us/azure/cosmos-db/mongodb/indexing

Azure Cosmos DB only supports a time-to-live (TTL) at the collection level (_ts) in version 3.2. Upgrade to versions 3.6+ to take advantage of other forms of TTL.

I will check internally if this is something that is enabled by our product group and will let you know shortly.

Regards,

Oury
Kris Lemoine 25 Reputation points

2024-07-23T06:27:45.2566667+00:00

It could be that the original version was 3.2 and that a previous update failed. The instances are already from the year 2020

The command we are using is

db.collection.createIndex({"ExpiryDate":1}, {expireAfterSeconds: 2592000})

MongoServerError[BadValue]: The 'expireAfterSeconds' option is supported on '_ts' field only.
Kris Lemoine 25 Reputation points

2024-07-23T06:33:28.94+00:00

@Oury Ba-MSFT any update?
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Jens Neubauer 80 Reputation points

2024-08-08T11:27:26.7266667+00:00

I'm having the same problem. My instance was created in 2020 and updated to 4.2 in February 2023. I've tried to update it all the way to 7.0, but I cannot create the TTL index on anything other than "_ts".

Accepted answer

Jens Neubauer 80 Reputation points

2024-08-08T11:54:25.42+00:00

I think I found the reason.

This page mentions the capability "EnableTtlOnCustomPath", but also states "This capability cannot be enabled on an Azure Cosmos DB for MongoDB accounts with continuous backup."

And of course continous backup cannot be disabled once it is enabled.

Edited to add: I was able to set the capability using Azure CLI and (after a while) was able to create a TTL index, even though the documentation says I shouldn't be able to...
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TTL on timestamp fields are not accepted on older instances of Azure Cosmo DB for MongoDB

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