Issue Summary

When requesting ~75 Confluence content elements by id (being pages, blogposts, embeds, databases, or whiteboards), we receive this error:

{
   "statusCode": 400,
   "message": "com.atlassian.confluence.api.service.exceptions.scale.SSStatusCodeException: CQL was parsed but the search manager was unable to execute the search. Error message: com.atlassian.confluence.api.service.exceptions.scale.SSStatusCodeException: There was an illegal request passed to XP-Search Aggregator API : HTTP/1.1 400 Bad Request"
}

This happens intermittently with more or fewer content IDs in the request. 

Steps to Reproduce

1. Send a request to https://developer.atlassian.com/cloud/confluence/rest/v1/api-group-search/#api-wiki-rest-api-search-get
2. Search for multiple IDs, example:

   https://<SITE>.atlassian.net/wiki/rest/api/search?cql=type in ('page','blogpost','whiteboard','embed','database') and id in (32773, 33021, 33154, 33165, 33186, 33195, 131078, 131084, 131090, 131096, (MORE_IDS), 21266451, 21987329, 22020103, 22020123, 22020130, 22020133, 22020136, 22020145)&limit=250 

3. The error is intermittent, but if it fails, it will look like this at the UI:
   
4. In the API response:

   {
      "statusCode": 400,
      "message": "com.Atlassian.confluence.api.service.exceptions.scale.SSStatusCodeException: CQL was parsed but the search manager was unable to execute the search. Error message: com.atlassian.confluence.api.service.exceptions.scale.SSStatusCodeException: There was an illegal request passed to XP-Search Aggregator API : HTTP/1.1 400 Bad Request"
   } 

5. Note that sometimes making the same request, it responds correctly. 

It appears that this error began last week. 

Expected Results

The API should return the corresponding content IDs or should give an error message with more information/clarification on the root cause. 

Actual Results

The exception below is thrown:

{    "statusCode": 400,    "message": "com.Atlassian.confluence.api.service.exceptions.scale.SSStatusCodeException: CQL was parsed but the search manager was unable to execute the search. Error message: com.atlassian.confluence.api.service.exceptions.scale.SSStatusCodeException: There was an illegal request passed to XP-Search Aggregator API : HTTP/1.1 400 Bad Request" }  

Workaround

Currently, there is no known workaround for this behavior. A workaround will be added here when available