Sampler Aggregationedit
This functionality is experimental and may be changed or removed completely in a future release.
A filtering aggregation used to limit any sub aggregations' processing to a sample of the top-scoring documents.
Example use cases:
- Tightening the focus of analytics to high-relevance matches rather than the potentially very long tail of low-quality matches
-
Reducing the running cost of aggregations that can produce useful results using only samples e.g.
significant_terms
Example:
{
"query": {
"match": {
"text": "iphone"
}
},
"aggs": {
"sample": {
"sampler": {
"shard_size": 200
},
"aggs": {
"keywords": {
"significant_terms": {
"field": "text"
}
}
}
}
}
}Response:
{
...
"aggregations": {
"sample": {
"doc_count": 1000,
"keywords": {
"doc_count": 1000,
"buckets": [
...
{
"key": "bend",
"doc_count": 58,
"score": 37.982536582524276,
"bg_count": 103
},
....
}
| 1000 documents were sampled in total because we asked for a maximum of 200 from an index with 5 shards. The cost of performing the nested significant_terms aggregation was therefore limited rather than unbounded. |
shard_sizeedit
The shard_size parameter limits how many top-scoring documents are collected in the sample processed on each shard.
The default value is 100.
Limitationsedit
Cannot be nested under breadth_first aggregationsedit
Being a quality-based filter the sampler aggregation needs access to the relevance score produced for each document.
It therefore cannot be nested under a terms aggregation which has the collect_mode switched from the default depth_first mode to breadth_first as this discards scores.
In this situation an error will be thrown.