sh.updateZoneKeyRange()
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Definition
sh.updateZoneKeyRange(namespace, minimum, maximum, zone)
New in version 3.4.
Associates a range of shard key values with a zone.
Starting in MongoDB 4.0.2, you can run
updateZoneKeyRange
database command and its helperssh.updateZoneKeyRange()
andsh.addTagRange()
on an unsharded collection or a non-existing collection.Important
mongo Shell Method
This page documents a
mongo
method. This is not the documentation for database commands or language-specific drivers, such as Node.js. To use the database command, see theupdateZoneKeyRange
command.For MongoDB API drivers, refer to the language-specific MongoDB driver documentation.
sh.updateZoneKeyRange()
takes the following arguments:ParameterTypeDescriptionnamespace
stringThe namespace of the sharded collection associate with the
zone
.The collection must be sharded for the operation to succeed.
minimum
documentThe inclusive lower bound of the range of shard key values.
Specify each field of the shard key in the form of
<fieldname> : <value>
. The value must be of the same BSON type or types as the shard key.maximum
documentThe exclusive upper bound of the range of shard key values.
Specify each field of the shard key in the form of
<fieldname> : <value>
. The value must be of the same BSON type or types as the shard key.zone
stringThe name of the zone to associate with the range of shard key values bounded byminimum
andmaximum
.Only issue
sh.updateZoneKeyRange()
when connected to amongos
instance.
Behavior
You cannot create a range of shard key values whose lower and upper boundaries
overlap with an existing range for the sharded collection. For example, given
an existing range of 1
to 10
, you cannot create a new range of 5
to 20
, as the new range would overlap with the existing range.
A zone can have multiple ranges of data associated with it, but a range can at most be associated with a single zone.
See the zone manual page for more information on zones in sharded clusters.
Initial Chunk Distribution for Empty or Non-Existing Collections
If you are considering performing zone sharding
on an empty or non-existent collection, use
sh.updateZoneKeyRange()
to create the zones and zone ranges
before sharding the collection (since 4.0.2). Starting in version
4.0.3, creating zones and zone ranges on empty or non-existing
collections allows MongoDB to optimize the initial chunk creation and
distribution process when sharding the collection. This optimized
process supports faster setup of zoned sharding with less balancer
overhead than creating zones after sharding. The balancer performs all chunk management after the optimized
initial chunk creation and distribution.
For an example of defining zones and zone ranges for initial chunk distribution, see Pre-Define Zones and Zone Ranges for an Empty or Non-Existing Collection.
Initial Chunk Distribution with Compound Hashed Shard Keys
Starting in version 4.4, MongoDB supports sharding collections on compound hashed indexes. MongoDB can perform optimized initial chunk creation and distribution when sharding the empty or non-existing collection on a compound hashed shard key.
If the hashed field is the prefix of the shard key (i.e. the first field in the shard key), all of the following must be true for MongoDB to perform initial chunk creation and distribution:
The collection has a single zone range with
MinKey
for all lower-bound fields andMaxKey
for all upper-bound fields.sh.shardCollection()
specifies the presplitHashedZones: true option.
If the hashed field is not the prefix of the shard key (i.e. the shard key has one or more non-hashed leading fields), all of the following must be true for MongoDB to perform initial chunk creation and distribution:
The collection has one zone range for each combination of distinct prefix field values (i.e. all fields preceding the hashed field).
For the lower-bound of each zone range, specify
MinKey
for the hashed field and all subsequent fields.For each zone range, at least one upper-bound prefix field must differ from its lower-bound counterpart.
sh.shardCollection()
specifies the presplitHashedZones: true option.
For a more complete example of defining zones and zone ranges for initial chunk distribution on a compound hashed shard key, see Pre-Define Zones and Zone Ranges for an Empty or Non-Existing Collection.
Balancer
After associating a range to a zone, the balancer must first run in order to migrate any chunks whose ranges are covered by the zone to shards inside of that zone. Until balancing completes, some chunks may reside on the wrong shard given the configured zones for the sharded cluster. See Balancer for more information.
See the sharded cluster balancer manual page for more information on how migrations work in a sharded cluster.
Bounds
Zone ranges are always inclusive of the lower boundary and exclusive of the upper boundary.
Dropped Collections
Dropping a collection deletes its associated zone/tag ranges.
In earlier versions, MongoDB does not remove the tag associations for a dropped collection, and if you later create a new collection with the same name, the old tag associations will apply to the new collection.
Security
For sharded clusters running with authentication, you must authenticate as either:
a user whose privileges include the specified actions on various collections in the
config
database:or, alternatively,
a user whose privileges include
enableSharding
on the cluster resource (available starting in version 4.2.2, 4.0.14, 3.6.16).
The clusterAdmin
or clusterManager
built-in roles have
the appropriate permissions for issuing sh.updateZoneKeyRange()
. See
the documentation page for Role-Based Access Control
for more information.
Examples
Given a sharded collection exampledb.collection
with a shard key of { a
: 1 }
, the following operation creates a range with a lower bound of 1
and an upper bound of 10
on the alpha
zone:
sh.updateZoneKeyRange( "exampledb.collection", { a : 1 }, { a : 10 }, "alpha" )
The following operation removes the previously created range by passing
null
to the zone
field.
sh.updateZoneKeyRange( "exampledb.collection", { a : 1 }, { a : 10 }, null )
The min
and max
must match exactly the bounds of the target range.
The following operation attempts to remove the previously created range, but
specifies { a : 0 }
as the min
bound:
sh.updateZoneKeyRange( "exampledb.collection", { a : 0 }, { a : 10 }, null )
While the range of { a : 0 }
and { a : 10 }
encompasses the existing
range, it is not an exact match and therefore updateZoneKeyRange
does not remove anything.
Compound Shard Key
Given a sharded collection exampledb.collection
with a shard key of { a
: 1, b : 1 }
, the following operation creates a range covering the lower
bound of { a: 1, b : 1 }
and an upper bound of { a : 10, b : 10}
and associates it
with the alpha
zone:
sh.updateZoneKeyRange( "exampledb.collection", { a : 1, b : 1 }, { a : 10, b : 10 }, "alpha" )
Pre-Define Zones and Zone Ranges for an Empty or Non-Existing Collection
Starting in version 4.2, creating zones and zone ranges on empty or non-existing collections allows MongoDB to optimize the initial chunk creation and distribution process when sharding the collection. This optimized process supports faster setup of zoned sharding with less balancer overhead than creating zones after sharding. The balancer performs all chunk management after the optimized initial chunk creation and distribution. See Initial Chunk Distribution with Compound Hashed Shard Keys for more information.
The sections below contain examples for three different shard key types.
Consider the following examples, which explore pre-defining zones or zone ranges for three different shard key types:
Single or Compound Shard Keys
Note
This example only applies to single-field or compound shard keys without a hashed field.
For example, { "zip" : 1 }
or
{ "zip" : 1, "account" : 1}
Create the Zones
Use sh.addShardToZone()
to create the zones:
sh.addShardToZone("shardA", "DC1") sh.addShardToZone("shardB", "DC2")
Create the Zone Ranges
Use sh.updateZoneKeyRange()
to create the ranges
for the empty contacts
collection in the exampledb
database:
sh.updateZoneKeyRange( "exampledb.contacts", { zip: 10001 }, { zip: 10090 }, "DC1" ); sh.updateZoneKeyRange( "exampledb.contacts", { zip: 90001 }, { zip: 96054 }, "DC2" );
Optional: Enable Sharding for the Database
Skip this step if you already enabled sharding on the database.
Use sh.enableSharding()
to enable sharding for the
database:
sh.enableSharding("exampledb")
Shard the Collection
Note
If the collection does not exist, the sharding operation creates the collection.
If the collection is empty and no index exists to support the shard key, the sharding operation creates the index.
Use sh.shardCollection()
to shard the collection contacts
:
sh.shardCollection("exampledb.contacts", { zip: 1 } );
Review the Created Chunks and Distribution
To see the created chunks and distribution, run the
sh.status()
operation:
sh.status()
The method returns:
--- Sharding Status --- sharding version: { "_id" : 1, "minCompatibleVersion" : 5, "currentVersion" : 6, "clusterId" : ObjectId("5b80c06d35a961fd0ae1986d") } shards: { "_id" : "shardA", "host" : "shardA/mongodb0.example.net:27018,mongodb1.example.net:27018,mongodb2.example.net:27018", "state" : 1, "tags" : [ "DC1" ] } { "_id" : "shardB", "host" : "shardB/mongodb3.example.net:27018,mongodb4.example.net:27018,mongodb5.example.net:27018", "state" : 1, "tags" : [ "DC2" ] } active mongoses: "4.2.0" : 2 autosplit: Currently enabled: yes balancer: Currently enabled: yes Currently running: no Failed balancer rounds in last 5 attempts: 0 Migration Results for the last 24 hours: No recent migrations databases: { "_id" : "config", "primary" : "config", "partitioned" : true } { "_id" : "exampledb", "primary" : "shardA", "partitioned" : true, "version" : { "uuid" : UUID("6c351bcf-acd2-4fd9-82d8-9f6bd7321558"), "lastMod" : 1 } } exampledb.contacts shard key: { "zip" : 1 } unique: false balancing: true chunks: shardA 3 shardB 2 { "zip" : { "$minKey" : 1 } } -->> { "zip" : 10001 } on : shardA Timestamp(1, 0) { "zip" : 10001 } -->> { "zip" : 10090 } on : shardA Timestamp(1, 1) { "zip" : 10090 } -->> { "zip" : 90001 } on : shardB Timestamp(1, 2) { "zip" : 90001 } -->> { "zip" : 96054 } on : shardB Timestamp(1, 3) { "zip" : 96054 } -->> { "zip" : { "$maxKey" : 1 } } on : shardA Timestamp(1, 4) tag: DC1 { "zip" : 10001 } -->> { "zip" : 10090 } tag: DC2 { "zip" : 90001 } -->> { "zip" : 96054 }
For the collection, sharding operation created 5 chunks (two chunks that correspond to the zone ranges and the other three to cover all other values) across shardA and shardB.
Compound Hashed Shard Key with Hashed Prefix
Note
This example only applies to compound hashed shard keys where the hashed field is the prefix of the shard key (i.e. the first field in the shard key is hashed).
For example, { "_id" : "hashed", "facility" : 1 }
Starting in version 4.4, MongoDB supports sharding collections on compound hashed indexes. When sharding on a compound hashed shard key, MongoDB can perform optimized initial chunk creation and distribution on the empty or non-existing collection only if the defined zone ranges meet additional requirements.
Consider an empty collection examples.metrics
which will store
analytics from one of two manufacturing facilities. The
planned shard key is { "_id" : "hashed", "facility" : 1}
,
where the hashed field is the shard key prefix.
Create the Zones
The planned shard key is { "_id" : "hashed", "facility" : 1 }
.
Since the hashed field is the prefix (i.e. the first field in the
shard key), create a single zone using
sh.addShardToZone()
:
sh.addShardToZone("shardA", "FacilityAlpha") sh.addShardToZone("shardB", "FacilityAlpha")
Create the Zone Ranges
Initial chunk distribution on a compound hashed shard key with a
hashed prefix requires a single zone range with MinKey
for all
lower-bound fields and MaxKey
for all upper-bound fields.
Use sh.updateZoneKeyRange()
to create a single range:
sh.updateZoneKeyRange( "examples.metrics", { "_id" : MinKey, "facility" : MinKey }, { "_id" : MaxKey, "facility" : MaxKey }, "FacilityAlpha" );
Optional: Enable Sharding for the Database
Skip this step if you already enabled sharding on the database.
Use sh.enableSharding()
to enable sharding for the
database:
sh.enableSharding("examples")
Shard the Collection
Note
If the collection does not exist, the sharding operation creates the collection.
If the collection is empty and no index exists to support the shard key, the sharding operation creates the index.
Use sh.shardCollection()
with
presplitHashedZones: true to shard the
collection and perform initial chunk creation and distribution:
sh.shardCollection( "examples.metrics", { "_id" : "hashed", "facility" : 1 }, false, { presplitHashedZones: true } )
Review the Created Chunks and Distribution
To see the created chunks and distribution, run the
sh.status()
operation:
sh.status()
The output resembles the following (content omitted for readability):
--- Sharding Status --- databases: { "_id" : "config", "primary" : "config", "partitioned" : true } { "_id" : "examples", "primary" : "shardA", "partitioned" : true, "version" : { "uuid" : UUID("245f8abf-a363-48b0-8208-2a5b577bbb4e"), "lastMod" : 1 } } examples.metrics shard key: { "_id" : "hashed", "facility" : 1 } unique: false balancing: true chunks: shardA 2 shardB 2 { "_id" : { "$minKey" : 1 }, "facility" : { "$minKey" : 1 } } -->> { "_id" : NumberLong("-4611686018427387902"), "facility" : { "$minKey" : 1 } } on : shardA Timestamp(1, 0) { "_id" : NumberLong("-4611686018427387902"), "facility" : { "$minKey" : 1 } } -->> { "_id" : NumberLong(0), "facility" : { "$minKey" : 1 } } on : shardA Timestamp(1, 1) { "_id" : NumberLong(0), "facility" : { "$minKey" : 1 } } -->> { "_id" : NumberLong("4611686018427387902"), "facility" : { "$minKey" : 1 } } on : shardB Timestamp(1, 2) { "_id" : NumberLong("4611686018427387902"), "facility" : { "$minKey" : 1 } } -->> { "_id" : { "$maxKey" : 1 }, "facility" : { "$maxKey" : 1 } } on : shardB Timestamp(1, 3) tag: FacilityAlpha { "_id" : { "$minKey" : 1 }, "facility" : { "$minKey" : 1 } } -->> { "_id" : { "$maxKey" : 1 }, "facility" : { "$maxKey" : 1 } }
The sharding operation produced 4 chunks in total. Two chunks
correspond to the absolute lower and upper bounds. One zone was
created on shardA
and shardB
corresponding to
FacilityAlpha
. The zone was subdivided into 2 chunks using the
hashed field.
Compound Hashed Shard Key with Non-Prefix Hashed Field
Note
This example only applies to compound hashed shard keys where the hashed field is not the prefix of the shard key (i.e. the first field in the shard key is not hashed).
For example, { "facility" : 1, "_id" : "hashed" }
Starting in version 4.4, MongoDB supports sharding collections on compound hashed indexes. When sharding on a compound hashed shard key, MongoDB can perform optimized initial chunk creation and distribution on the empty or non-existing collection only if the defined zone ranges meet additional requirements.
Consider an empty collection examples.metrics
which will store
analytics from one of two manufacturing facilities. The planned
shard key is { "facility" : 1, "_id" : "hashed" }
, where
the hashed field is not the shard key prefix.
The
facility
field stores the name of the facility:"FacilityAlpha"
or"FacilityBaker"
. The collection requires zone ranges onfacility
to help isolate data for each facility to specific shards.The
_id
field compensates for the low-cardinality of thefacility
field. Hashing compensates for the monotonically-increasing nature of the_id
field.
Create the Zones
Use the sh.addShardToZone()
command to create the
zones.
sh.addShardToZone("shardA", "FacilityAlpha") sh.addShardToZone("shardB", "FacilityBaker")
Create the Zone Ranges
The planned shard key is {"facility" : 1, "_id" : "hashed"}
. The
facility
field has two possible values: FacilityAlpha
and
FacilityBaker
.
Initial chunk distribution on a compound hashed shard key where the
hashed field is not the prefix requires one zone range for each
combination of distinct prefix field values (i.e. all fields
preceding the hashed field). Since facility
has two distinct
prefix values, the collection requires exactly two zone ranges
that cover those values.
The lower bound range specifies
MinKey
for all non-prefix fields.The upper-bound range has at least one prefix field that differs from its lower-bound counterpart.
Use sh.updateZoneKeyRange()
to create the range for
"facility": "FacilityAlpha"
:
sh.updateZoneKeyRange( "examples.metrics", { "facility": "FacilityAlpha", "_id" : MinKey }, { "facility": "FacilityBaker", "_id" : MinKey }, "FacilityAlpha" );
Since zone range upper bounds are exclusive, this range only covers documents with the distinct shard key prefix value
"facilty" : "FacilityAlpha"
and all possible values of_id
.
Use sh.updateZoneKeyRange()
to create the range for
"facility": "FacilityBaker"
:
sh.updateZoneKeyRange( "examples.metrics", { "facility": "FacilityBaker", "_id" : MinKey }, { "facility": MaxKey, "_id" : MinKey }, "FacilityBaker" );
While the upper bound of this range can technically capture other values of
facility
, the initial chunk distribution logic relies on the assumption that no other distinct values forfacility
exist. Since the collection only contains documents wherefacility
isFacilityAlpha
orFacilityBaker
, this range only covers documents with the distinct shard key prefix value"facility" : "FacilityBaker"
and all possible values of_id
.
Optional: Enable Sharding for the Database
Skip this step if you already enabled sharding on the database.
Use sh.enableSharding()
to enable sharding for the
database:
sh.enableSharding("examples")
Shard the Collection
Note
If the collection does not exist, the sharding operation creates the collection.
If the collection is empty and no index exists to support the shard key, the sharding operation creates the index.
Use sh.shardCollection()
with
presplitHashedZones: true to shard the
collection and perform initial chunk creation and distribution:
sh.shardCollection( "examples.metrics", { "facility" : 1, "_id" : "hashed"}, false, { presplitHashedZones: true } )
Review the Created Chunks and Distribution
To see the created chunks and distribution, run the
sh.status()
operation:
sh.status()
The output resembles the following (content omitted for readability):
--- Sharding Status --- databases: { "_id" : "config", "primary" : "config", "partitioned" : true } { "_id" : "examples", "primary" : "shardA", "partitioned" : true, "version" : { "uuid" : UUID("6c351bcf-acd2-4fd9-82d8-9f6bd7321558"), "lastMod" : 1 } } examples.metrics shard key: { "facility" : 1, "_id" : "hashed" } unique: false balancing: true chunks: shardA 3 shardB 3 { "facility" : { "$minKey" : 1 }, "_id" : { "$minKey" : 1 } } -->> { "facility" : "FacilityAlpha", "_id" : { "$minKey" : 1 } } on : shard1 Timestamp(1, 0) { "facility" : "FacilityAlpha", "_id" : { "$minKey" : 1 } } -->> { "facility" : "FacilityAlpha", "_id" : NumberLong(0) } on : shard1 Timestamp(1, 1) { "facility" : "FacilityAlpha", "_id" : NumberLong(0) } -->> { "facility" : "FacilityBaker", "_id" : { "$minKey" : 1 } } on : shard1 Timestamp(1, 2) { "facility" : "FacilityBaker", "_id" : { "$minKey" : 1 } } -->> { "facility" : "FacilityBaker", "_id" : NumberLong(0) } on : shard2 Timestamp(1, 3) { "facility" : "FacilityBaker", "_id" : NumberLong(0) } -->> { "facility" : { "$maxKey" : 1 }, "_id" : { "$minKey" : 1 } } on : shard2 Timestamp(1, 4) { "facility" : { "$maxKey" : 1 }, "_id" : { "$minKey" : 1 } } -->> { "facility" : { "$maxKey" : 1 }, "_id" : { "$maxKey" : 1 } } on : shard2 Timestamp(1, 5) tag: FacilityAlpha { "facility" : "FacilityAlpha", "_id" : { "$minKey" : 1 } } -->> { "facility" : "FacilityBaker", "_id" : { "$minKey" : 1 } } tag: FacilityBaker { "facility" : "FacilityBaker", "_id" : { "$minKey" : 1 } } -->> { "facility" : { "$maxKey" : 1 }, "_id" : { "$minKey" : 1 } }
The sharding operation produced 6 chunks in total. Two chunks
correspond to the absolute lower and upper bounds. Two zones were
created, one on shardA
and one on shardB
, corresponding to
FacilityAlpha
and FacilityBaker
. Each of these zones has been
further subdivided into 2 chunks using the hashed field.