[druid-user] merge multi-value field on rollout/compaction

Hi folks,
Need you help

Is there any way to ask druid to merge multi value dimension field on rollout?

I want to add a field to my druid table , but I don’t want to increase the cardinality the current rows.


I’m not exactly clear on what you want to do, but maybe this will be helpful.

If you currently have a multi-valued dimension (MVD), and want to add a value into it, I think it should be possible using reindexing.
(Compaction or rollup affect metrics, not dimensions, and an MVD can’t be a metric afaik.)

What I think you could do is use a transform on the dimension, with array_concat to add the new value to the existing MVD (array).