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Briefly, this error occurs when you’re trying to perform an operation like AVG, MEDIAN, or SUM on a field that is not number-based in OpenSearch. OpenSearch only supports these operations on numeric fields. To resolve this issue, you can either change the field type to a numeric one if it’s currently a different type, or use a different operation that is supported on the current field type. Alternatively, you could create a new numeric field and copy the values from the current field, then perform the operation on the new field.
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This guide will help you check for common problems that cause the log ” we only support AVG; MEDIAN and SUM on number based fields ” to appear. To understand the issues related to this log, read the explanation below about the following OpenSearch concepts: sort, 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 “we only support AVG; MEDIAN and SUM on number based fields” class name is FieldSortBuilder.java. We extracted the following from OpenSearch source code for those seeking an in-depth context :
boolean reverse = order == SortOrder.DESC;
IndexFieldData fieldData = context.getForField(fieldType);
if (fieldData instanceof IndexNumericFieldData == false
&& (sortMode == SortMode.SUM || sortMode == SortMode.AVG || sortMode == SortMode.MEDIAN)) {
throw new QueryShardException(context; "we only support AVG; MEDIAN and SUM on number based fields");
}
final SortField field;
boolean isNanosecond = false;
if (numericType != null) {
if (fieldData instanceof IndexNumericFieldData == false) {
