Diversified sampler aggregation

Diversified sampler aggregation #

Like sampler, but the sample is diversified by a field — up to one (or few) documents per value — so rare categories survive the sampling. A plain sampler can be flooded by the most common value (every sampled type being t-shirt); the diversified variant guarantees representation for every distinct value first.

How it works #

The sampler walks the matching documents in two passes. First it caps each distinct value of the diversify field at max_docs_per_value (default 1) — extra documents with an already-full value are dropped. Documents missing the diversify field share one common group. The survivors are then sorted and truncated to the overall shard_size (default 100).