Summary

Switch the collection-level change-stream updateLookup path from the Express executor to
SbeSingleDocumentLookupExecutor in change_stream_add_post_image_stage_fn.cpp. Database and
cluster streams keep Express (their lookup namespace varies per event); both fall back to the routed
Aggregation executor when the document is not local.

Details

• Executor selection keys on ChangeStream::getChangeStreamType(nss) == kCollection.
• Only the collection-level SBE path buffers more than one event (gated on internalChangeStreamUpdateLookupMaxBatchSize, default 1); db/cluster and the unoptimized path stay batch-of-one.

Depends on

SERVER-129528.