Aggregation on non-indexed fields

[Sundar_V]

Hello,

We are having in one ES 5.4, with 3 nodes and in total 80 shard.

We have 800 million documents in these shards. When we are aggregating on certain fields, we see that it is very slow.

The fields we are aggregating are count and millisecond.

"count": {
  "type": "long",
  "doc_values": true
},
"millisecond": {
  "type": "scaled_float",
  "scaling_factor": 100,
  "doc_values": true
},

We are not searching these fields, only aggregating. Should these be indexed?

From an old thread, it seems that indexing is not needed. https://github.com/elastic/elasticsearch/issues/9762#issuecomment-75062924

Is that still valid with the new ES 5.x?

Thanks
Sundar.

[ddorian43]

Yep. Agg uses doc_values. You can try profile the query.