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A user reported that the same query that takes ~900ms when querying an index pattern only takes ~50ms when only querying indices that have matches. The query is a date range query and we confirmed that the `can_match` phase works as expected. I was able to reproduce this issue locally with a single node: with 900 1-shard indices, a query to an index pattern that matches all indices runs in ~90ms while a query to the only index that has matches runs in 0-1ms. This ended up not being related to the `can_match` phase but to the cost of resolving aliases when querying an index pattern that matches lots of indices. In that case, we first resolve the index pattern to a list of concrete indices and then for each concrete index, we check whether it was matched through an alias, meaning we might have to apply alias filters. Unfortunately this second per-index operation runs in linear time with the number of matched concrete indices, which means that alias resolution runs in O(num_indices^2) overall. So queries get exponentially slower as an index pattern matches more indices. I reorganized alias resolution into a one-step operation that runs in linear time with the number of matches indices, and then a per-index operation that runs in linear time with the number of aliases of this index. This makes alias resolution run is O(num_indices * num_aliases_per_index) overall instead. When testing the scenario described above, the `took` went down from ~90ms to ~10ms. It is still more than the 0-1ms latency that one gets when only querying the single index that has data, but still much better than what we had before. Closes #40248 |
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Elasticsearch REST API JSON specification
This repository contains a collection of JSON files which describe the Elasticsearch HTTP API.
Their purpose is to formalize and standardize the API, to facilitate development of libraries and integrations.
Example for the "Create Index" API:
{
"indices.create": {
"documentation": "http://www.elastic.co/guide/en/elasticsearch/reference/master/indices-create-index.html",
"methods": ["PUT", "POST"],
"url": {
"path": "/{index}",
"paths": ["/{index}"],
"parts": {
"index": {
"type" : "string",
"required" : true,
"description" : "The name of the index"
}
},
"params": {
"timeout": {
"type" : "time",
"description" : "Explicit operation timeout"
}
}
},
"body": {
"description" : "The configuration for the index (`settings` and `mappings`)"
}
}
}
The specification contains:
- The name of the API (
indices.create), which usually corresponds to the client calls - Link to the documentation at http://elastic.co
- List of HTTP methods for the endpoint
- URL specification: path, parts, parameters
- Whether body is allowed for the endpoint or not and its description
The methods and url.paths elements list all possible HTTP methods and URLs for the endpoint;
it is the responsibility of the developer to use this information for a sensible API on the target platform.
License
This software is licensed under the Apache License, version 2 ("ALv2").