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SHARD_MERGE

Short Description

Merging results from shards

Detailed Description​

SHARD_MERGE in a MongoDB explain plan is an execution stage that appears in sharded cluster environments.

In simple terms:

  • SHARD_MERGE happens when MongoDB needs to gather results from multiple shards (individual databases that hold parts of your data in a sharded cluster) and combine them into a single unified result set.
  • It’s responsible for merging and organizing data that comes from different shards according to your query’s requirements (such as sorting or pagination).

When do you see SHARD_MERGE?

  • When running queries in a sharded cluster that require data from more than one shard to be combined before returning results to the client.

Summary:

SHARD_MERGE means MongoDB is merging and assembling results from multiple shards in a sharded cluster to return to you as a single, complete result set. This is a crucial part of distributed query processing in sharded collections.

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