Answer
$merge writes aggregation results into a target collection, supporting upserts and replacements useful for ETL workflows.
Quick Answer
$merge writes aggregation pipeline results to a collection (either inserting or merging into existing documents). More flexible than $out (which replaces the whole collection). You can specify what to do when a matching document exists: replace, merge, keep existing, fail, or run a custom pipeline. Use for building materialized views or pre-aggregated reports.
S
SugharaIQ Editorial Team
Verified Answer
This answer has been peer-reviewed by industry experts holding senior engineering roles to ensure technical accuracy and relevance for modern interview standards.
Want to bookmark, take notes, or join discussions?
Sign in to access all features and personalize your learning experience.
Source: SugharaIQ