How to Fix MongoDB Error Code – 61 – ShardKeyNotFound

MongoDB is a popular NoSQL database that offers high scalability and flexibility. However, like any other software, it can encounter errors that need to be resolved. One such error is the MongoDB Error Code – 61 – ShardKeyNotFound. In this article, we will explore what this error means and how to fix it.

Understanding MongoDB Error Code – 61 – ShardKeyNotFound

The ShardKeyNotFound error occurs when MongoDB cannot find the shard key in a sharded collection. The shard key is a field or a combination of fields that determines how data is distributed across shards in a sharded cluster. When executing a query, MongoDB uses the shard key to determine which shard(s) to search for the requested data.

If the shard key is not found, MongoDB cannot route the query to the appropriate shard(s), resulting in the ShardKeyNotFound error. This error typically occurs when querying a sharded collection without specifying the shard key or when the shard key value is missing or incorrect.

Fixing the ShardKeyNotFound Error

To fix the ShardKeyNotFound error, you need to ensure that the shard key is present and correctly specified in your queries. Here are some steps to follow:

1. Verify the Shard Key

First, verify that the shard key is correctly defined for the sharded collection. You can use the sh.status() command in the MongoDB shell to check the shard key configuration. Ensure that the shard key field(s) exist and are correctly specified.

sh.status()

2. Check Query Syntax

Review your query syntax to ensure that you are specifying the shard key correctly. The shard key should be included in the query predicate to allow MongoDB to route the query to the appropriate shard(s). For example:

db.collection.find({ shardKeyField: "value" })

Replace collection with the name of your sharded collection and shardKeyField with the actual shard key field name.

3. Verify Shard Key Value

Double-check that the shard key value exists and is correct. If the shard key value is missing or incorrect, MongoDB will not be able to find the appropriate shard(s) and will throw the ShardKeyNotFound error. Ensure that the shard key value is present and matches the data in your sharded collection.

4. Resharding

If you have recently modified the shard key or added new shards to your cluster, you may need to perform a resharding operation. Resharding redistributes the data across shards based on the new shard key configuration. You can use the sh.shardCollection() command to initiate the resharding process.

sh.shardCollection("database.collection", { shardKeyField: 1 })

Replace database.collection with the name of your sharded collection and shardKeyField with the actual shard key field name.

Summary

The MongoDB Error Code – 61 – ShardKeyNotFound occurs when MongoDB cannot find the shard key in a sharded collection. To fix this error, verify the shard key configuration, check query syntax, ensure the shard key value is correct, and perform resharding if necessary.

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