Sharding Reference

Sharding Methods in `mongosh`

Name	Description
`convertShardKeyToHashed()`	Returns the hashed value for the input.
`db.checkMetadataConsistency()`	Checks the cluster or database for inconsistent sharding metadata. New in version 7.0.
`db.collection.checkMetadataConsistency()`	Checks the collection for inconsistent sharding metadata. New in version 7.0.
`sh.abortMoveCollection()`	Stops an in-progress `moveCollection` operation. New in version 8.0.
`sh.abortReshardCollection()`	Aborts a resharding operation. New in version 5.0.
`sh.addShard()`	Adds a shard to a sharded cluster.
`sh.addShardTag()`	This method aliases to `sh.addShardToZone()`.
`sh.addShardToZone()`	Associates a shard to a zone. Supports configuring zones in sharded clusters.
`sh.addTagRange()`	This method aliases to `sh.updateZoneKeyRange()`.
`sh.balancerCollectionStatus()`	Returns information on whether the chunks of a sharded collection are balanced.
`sh.checkMetadataConsistency()`	Checks the cluster for inconsistent sharding metadata. New in version 7.0.
`sh.commitReshardCollection()`	Forces a resharding operation to block writes and complete. New in version 5.0.
`sh.disableAutoMerger()`	Disables automatic chunk merges for a namespace. New in version 7.0.
`sh.disableAutoSplit()`	Disables auto-splitting for the sharded cluster. Starting in MongoDB 6.0.3, automatic chunk splitting is not performed. This is because of balancing policy improvements. Auto-splitting commands still exist, but do not perform an operation.
`sh.disableBalancing()`	Disable balancing on a single collection in a sharded database. Does not affect balancing of other collections in a sharded cluster.
`sh.enableAutoMerger()`	Enables automatic chunk merges for a namespace. New in version 7.0.
`sh.enableAutoSplit()`	Enables auto-splitting for the sharded cluster. Starting in MongoDB 6.0.3, automatic chunk splitting is not performed. This is because of balancing policy improvements. Auto-splitting commands still exist, but do not perform an operation.
`sh.enableBalancing()`	Activates the sharded collection balancer process if previously disabled using `sh.disableBalancing()`.
`sh.enableSharding()`	Creates a database.
`sh.getBalancerState()`	Returns a boolean to report if the balancer is currently enabled.
`sh.getShardedDataDistribution()`	Returns data distribution information for sharded collections. `sh.getShardedDataDistribution()` is a shell helper method for the `$shardedDataDistribution` aggregation pipeline stage.
`sh.help()`	Returns help text for the `sh` methods.
`sh.isBalancerRunning()`	Returns a document describing the status of the balancer.
`sh.isConfigShardEnabled()`	Returns whether a cluster has a config shard. If it does, `sh.isConfigShardEnabled()` also returns host and tag information.
`sh.listShards()`	Returns an array of documents describing the shards in a sharded cluster.
`sh.moveChunk()`	Migrates a chunk in a sharded cluster.
`sh.moveCollection()`	Moves a single unsharded collection to a different shard.
`sh.moveRange()`	Move ranges between shards.
`sh.removeRangeFromZone()`	Removes an association between a range of shard keys and a zone. Supports configuring zones in sharded clusters.
`sh.removeShardTag()`	This method aliases to `sh.removeShardFromZone()`.
`sh.removeShardFromZone()`	Removes the association between a shard and a zone. Use to manage zone sharding.
`sh.removeTagRange()`	This method aliases to `sh.removeRangeFromZone()`.
`sh.reshardCollection()`	Initiates a resharding operation to change the shard key for a collection, changing the distribution of your data. New in version 5.0.
`sh.setBalancerState()`	Enables or disables the balancer which migrates chunks between shards.
`sh.shardAndDistributeCollection()`	Shards a collection and immediately redistributes the data using the provided shard key. New in version 8.0.
`sh.shardCollection()`	Enables sharding for a collection.
`sh.splitAt()`	Divides an existing chunk into two chunks using a specific value of the shard key as the dividing point.
`sh.splitFind()`	Divides an existing chunk that contains a document matching a query into two approximately equal chunks.
`sh.startAutoMerger()`	Enables the AutoMerger. New in version 7.0.
`sh.startBalancer()`	Enables the balancer and waits for balancing to start.
`sh.status()`	Reports on the status of a sharded cluster, as `db.printShardingStatus()`.
`sh.stopAutoMerger()`	Disables the AutoMerger. New in version 7.0.
`sh.stopBalancer()`	Disables the balancer and waits for any in progress balancing rounds to complete.
`sh.unshardCollection()`	Unshards an existing sharded collection and moves the collection data onto a single shard. When you unshard a collection, the collection cannot be partitioned across multiple shards and the shard key is removed. New in version 8.0.
`sh.updateZoneKeyRange()`	Associates a range of shard keys to a zone. Supports configuring zones in sharded clusters.
`sh.waitForBalancer()`	Internal. Waits for the balancer state to change.
`sh.waitForBalancerOff()`	Internal. Waits until the balancer stops running.
`sh.waitForPingChange()`	Internal. Waits for a change in ping state from one of the `mongos` in the sharded cluster.

Sharding Database Commands

The following database commands support sharded clusters.

Name	Description
`abortMoveCollection`	Stops an in-progress `moveCollection` operation. New in version 8.0.
`abortReshardCollection`	Aborts a resharding operation. New in version 5.0.
`addShard`	Adds a shard to a sharded cluster.
`addShardToZone`	Associates a shard with a zone. Supports configuring zones in sharded clusters.
`balancerCollectionStatus`	Returns information on whether the chunks of a sharded collection are balanced.
`balancerStart`	Starts a balancer thread.
`balancerStatus`	Returns information on the balancer status.
`balancerStop`	Stops the balancer thread.
`clearJumboFlag`	Clears the `jumbo` flag for a chunk.
`cleanupReshardCollection`	Cleans up a failed resharding operation. New in version 5.0.
`commitReshardCollection`	Forces a resharding operation to block writes and complete. New in version 5.0.
`enableSharding`	Enables sharding on a specific database.
`flushRouterConfig`	Forces a `mongod` / `mongos` instance to update its cached routing metadata.
`getShardMap`	Internal command that reports on the state of a sharded cluster.
`isdbgrid`	Verifies that a process is a `mongos`.
`listShards`	Returns a list of configured shards.
`moveChunk`	Internal command that migrates chunks between shards.
`moveCollection`	Moves a single unsharded collection to a different shard.
`movePrimary`	Reassigns the primary shard when removing a shard from a sharded cluster.
`moveRange`	Command that migrates ranges between shards.
`mergeChunks`	Provides the ability to combine chunks on a single shard.
`removeShard`	Starts the process of removing a shard from a sharded cluster.
`removeShardFromZone`	Removes the association between a shard and a zone. Supports configuring zones in sharded clusters.
`reshardCollection`	Initiates a resharding operation to change the shard key for a collection, changing the distribution of your data. New in version 5.0.
`shardCollection`	Enables the sharding functionality for a collection, allowing the collection to be sharded.
`shardingState`	Reports whether the `mongod` is a member of a sharded cluster.
`split`	Creates a new chunk.
`unsetSharding`	Removed in MongoDB 5.0. Internal command that affects connections between instances in a MongoDB deployment.
`updateZoneKeyRange`	Adds or removes the association between a range of sharded data and a zone. Supports configuring zones in sharded clusters.

Reference Documentation

Operational Restrictions: Requirement for deploying a sharded cluster
Troubleshoot Sharded Clusters: Common strategies for troubleshooting sharded cluster deployments.
Config Database: Complete documentation of the content of the local database that MongoDB uses to store sharded cluster metadata.

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Resharding for Adding and Removing Shards

Config Database

Sharding Reference

Sharding Methods in mongosh

Sharding Database Commands

Reference Documentation

Sharding Methods in `mongosh`