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Briefly, this error occurs when OpenSearch is trying to execute a nested aggregation but the path field, which is necessary to locate the nested documents, is missing. To resolve this issue, ensure that the path field is correctly specified in the nested aggregation query. The path should point to the nested field in the document. Also, verify that the field you’re trying to aggregate is indeed a nested type. If it’s not, you may need to reindex your data with the correct mapping or adjust your query to match the existing data structure.
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This guide will help you check for common problems that cause the log ” Missing [path] field for nested aggregation [” + aggregationName + “] ” to appear. To understand the issues related to this log, read the explanation below about the following OpenSearch concepts: aggregations, search.
Quick links
Overview
Search refers to the searching of documents in an index or multiple indices. The simple search is just a GET API request to the _search endpoint. The search query can either be provided in query string or through a request body.
Examples
When looking for any documents in this index, if search parameters are not provided, every document is a hit and by default 10 hits will be returned.
GET my_documents/_search
A JSON object is returned in response to a search query. A 200 response code means the request was completed successfully.
{
"took" : 1,
"timed_out" : false,
"_shards" : {
"total" : 2,
"successful" : 2,
"failed" : 0
},
"hits" : {
"total" : 2,
"max_score" : 1.0,
"hits" : [
...
]
}
}Notes and good things to know
- Distributed search is challenging and every shard of the index needs to be searched for hits, and then those hits are combined into a single sorted list as a final result.
- There are two phases of search: the query phase and the fetch phase.
- In the query phase, the query is executed on each shard locally and top hits are returned to the coordinating node. The coordinating node merges the results and creates a global sorted list.
- In the fetch phase, the coordinating node brings the actual documents for those hit IDs and returns them to the requesting client.
- A coordinating node needs enough memory and CPU in order to handle the fetch phase.
Log Context
Log “Missing [path] field for nested aggregation [” + aggregationName + “]” class name is NestedAggregationBuilder.java. We extracted the following from OpenSearch source code for those seeking an in-depth context :
}
} if (path == null) {
// "field" doesn't exist; so we fall back to the context of the ancestors
throw new ParsingException(parser.getTokenLocation(); "Missing [path] field for nested aggregation [" + aggregationName + "]");
} return new NestedAggregationBuilder(aggregationName; path);
}
