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DATAMONGO-2341 - Polishing.

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Inline MongoPersistentEntity.idPropertyIsShardKey() into UpdateContext. Move mapped shard key cache to QueryOperations level. Simplify conditionals. Tweak documentation.

Original pull request: #833.
This commit is contained in:
Mark Paluch
2020-02-17 10:11:26 +01:00
parent 6259cd2c3b
commit 22ca597fca
12 changed files with 143 additions and 122 deletions
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1
src/main/asciidoc/new-features.adoc
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@@ -8,6 +8,7 @@
* Support for <<mongo-template.aggregation-update,aggregation pipelines in update operations>>.
* Removal of `_id` flattening for composite Id's when using `MongoTemplate` aggregations.
* Apply pagination when using GridFS `find(Query)`.
* <<sharding,Sharding key derivation>> via `@Sharded`.
[[new-features.2-2-0]]
== What's New in Spring Data MongoDB 2.2

40
src/main/asciidoc/reference/sharding.adoc
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@@ -1,12 +1,13 @@
[[sharding]]
= Sharding
MongoDB supports large data sets via sharding, a method for distributing data across multiple machines. Please refer to the https://docs.mongodb.com/manual/sharding/[MongoDB Documentation] to learn how to set up a sharded cluster, its requirements and limitations.
MongoDB supports large data sets via sharding, a method for distributing data across multiple database servers.
Please refer to the https://docs.mongodb.com/manual/sharding/[MongoDB Documentation] to learn how to set up a sharded cluster, its requirements and limitations.
Spring Data MongoDB uses the `@Sharded` annotation to identify entities stored in sharded collections as shown below.
====
[source, java]
[source,java]
----
@Document("users")
@Sharded(shardKey = { "country", "userId" }) <1>
@@ -21,23 +22,24 @@ public class User {
String country;
}
----
<1> The properties of the shard key are mapped to the actual field names. See
<1> The properties of the shard key get mapped to the actual field names.
====
[[sharding.sharded-collections]]
== Sharded Collections
Spring Data MongoDB does not auto set up sharding for collections nor indexes required for it. The snippet below shows how to do so using the MongoDB client API.
Spring Data MongoDB does not auto set up sharding for collections nor indexes required for it.
The snippet below shows how to do so using the MongoDB client API.
====
[source, java]
[source,java]
----
MongoDatabase adminDB = template.getMongoDbFactory()
.getMongoDatabase("admin"); <1>
.getMongoDatabase("admin"); <1>
adminDB.runCommand(new Document("enableSharding", "db")); <2>
adminDB.runCommand(new Document("enableSharding", "db")); <2>
Document shardCmd = new Document("shardCollection", "db.users") <3>
Document shardCmd = new Document("shardCollection", "db.users") <3>
.append("key", new Document("country", 1).append("userid", 1)); <4>
adminDB.runCommand(shardCmd);
@@ -45,24 +47,28 @@ adminDB.runCommand(shardCmd);
<1> Sharding commands need to be run against the _admin_ database.
<2> Enable sharding for a specific database if necessary.
<3> Shard a collection within the database having sharding enabled.
<4> Set the shard key (Range based sharding in this case).
<4> Specify the shard key.
This example uses range based sharding.
====
[[sharding.shard-key]]
== Shard Key Handling
The shard key consists of a single or multiple properties present in every document within the target collection, and is used to distribute them across shards.
The shard key consists of a single or multiple properties that must exist in every document in the target collection.
It is used to distribute documents across shards.
Adding the `@Sharded` annotation to an entity enables Spring Data MongoDB to do best effort optimisations required for sharded scenarios when using repositories.
This means essentially adding required shard key information, if not already present, to `replaceOne` filter queries when upserting entities. This may require an additional server round trip to determine the actual value of the current shard key.
Adding the `@Sharded` annotation to an entity enables Spring Data MongoDB to apply best effort optimisations required for sharded scenarios.
This means essentially adding required shard key information, if not already present, to `replaceOne` filter queries when upserting entities.
This may require an additional server round trip to determine the actual value of the current shard key.
TIP: By setting `@Sharded(immutableKey = true)` no attempt will be made to check if an entities shard key changed.
TIP: By setting `@Sharded(immutableKey = true)` Spring Data does not attempt to check if an entity shard key was changed.
Please see the https://docs.mongodb.com/manual/reference/method/db.collection.replaceOne/#upsert[MongoDB Documentation] for further details and the list below for which operations are eligible for auto include the shard key.
Please see the https://docs.mongodb.com/manual/reference/method/db.collection.replaceOne/#upsert[MongoDB Documentation] for further details.
The following list contains which operations are eligible for shard key auto-inclusion:
* `Reactive/CrudRepository.save(...)`
* `Reactive/CrudRepository.saveAll(...)`
* `Reactive/MongoTemplate.save(...)`
* `(Reactive)CrudRepository.save(…)`
* `(Reactive)CrudRepository.saveAll(…)`
* `(Reactive)MongoTemplate.save(…)`