Parameter index on type dense_vector deprecation log

Elastic Stack Elasticsearch
1

I have a dynamic template with the mapping like this
"mapping": { "type": "dense_vector", "dims": 42, "index": false }

And I receive this deprecation log:
Parameter [index] has no effect on type [dense_vector] and will be removed in future

I'm using Elasticsearch 7.17 and planning to migrate to 8.13. The documentation on version 8.13 does mention the use of indexing on type dense_vector (ref). It also mentions that we can disable indexing by setting index to false (ref). So I wonder whether I should ignore it or not because the log level is critical but it seems to be a legit function and removing it may trade off some of the performance.

Please help me explain why there is that deprecation log and whether I should keep the setting or not. Many thanks.

2

You can add dense_vector fields with index: false but please note that the vectors have to be indexed in order to perform approximate knn search. This is why we enable indexing for default for dense_vector fields. If you index these with index: false in 7.x and want to use this functionality when you upgrade to 8.x you will have to reindex to a new index with index: true to use it.

If index is set to false you can still use brute force knn.

3

So does this mean that I can ignore the deprecation log? Why is it there anyway?

4

I think your confusion stems from the fact that you're using an older version and vector search is quickly evolving. Support for indexing vectors was added in 8.0.0.