Once CLOUD-140680 is also completed, $search, $vectorSearch, and $searchMeta explain queries with verbosity “executionStats” and “allPlansExecution” will now act like other stages and return documents instead of always returning EOF. “nReturned” and “executionTimeMillisEstimate” will now be populated for these stages.

Description of Linked Ticket

Summary

When users call explain("executionStats") on a pipeline with $search, they are not getting metrics and timings on how long subsequent aggregations stages took. Search does not return any documents during explain no matter what the mode is, this project should change that to bring it in line with other stages.

Motivation

$search not implementing explain harms diagnosis of failing and slow running queries. As search adoption increases we need to provide more tools to allow users to debug their own pipelines.

Documentation

Product Description
Scope
Technical Design
Docs Update