Notes

[ric2b]

Relevant files?

• s/
  • s/shard_util
  • s/shard_id
  • s/shard_key_pattern
  • s/sharding_initialization
  • s/chunk_manager
  • s/chunk_manager_targeter
  • s/cluster_identity_loader
  • s/config
  • s/grid
• db/
  • db/s/
  • db/s/sharding_state
  • db/s/collection_sharding_state
  • db/catalog
  • db/catalog/index_create
  • db/catalog/index_key_validate
  • db/ops/insert
  • db/index/
  • db/geo/

[ric2b]

Important files

• s/
  • commands/
  • cluster_shard_collection_cmd.cpp/h
  • grid.cpp/h
  • shard_key_pattern.cpp/h
• db/
  • keypattern.cpp/h
  • keypattern_test.cpp
• base/
  • error_codes.err

[ric2b]

cluster_shard_collection_cmd -> shard_key_pattern -> keypattern

[ric2b]

shard_key_pattern.cpp -> add bool ShardKeyPattern::isGeoPattern() ?

[ric2b]

keypattern.cpp -> add static bool is GeoKeyPattern(const BSONObj& pattern)?

[ric2b]

Valid and non-valid index keys: \db\catalog\index_key_validate_test.cpp

[ric2b]

Files where enableSharding is mentioned but I don't know what they do: src/mongo/s/config.cpp src/mongo/s/config.h src/mongo/s/catalog/sharding_catalog_client.h src/mongo/s/catalog/sharding_catalog_client_impl.cpp src/mongo/s/catalog/sharding_catalog_client_impl.h

[ric2b]

s/grid.h

/**
 * Holds the global sharding context. Single instance exists for a running server. Exists on
 * both MongoD and MongoS.
 */

s/grid.h::catalogClient

/**
 * Returns a pointer to a ShardingCatalogClient to use for accessing catalog data stored on the
 * config servers.
*/

catalogClient::enableSharding

/**
 * Creates a new database or updates the sharding status for an existing one. Cannot be
 * used for the admin/config/local DBs, which should not be created or sharded manually
 * anyways.
 *
 * Returns Status::OK on success or any error code indicating the failure. These are some
 * of the known failures:
 *  - DatabaseDifferCase - database already exists, but with a different case
 *  - ShardNotFound - could not find a shard to place the DB on
 */

[ric2b]

s/commands/cluster_shard_collection.cpp

// The proposed shard key must be validated against the set of existing indexes.
// In particular, we must ensure the following constraints
//
// 1. All existing unique indexes, except those which start with the _id index,
//    must contain the proposed key as a prefix (uniqueness of the _id index is
//    ensured by the _id generation process or guaranteed by the user).
//
// 2. If the collection is not empty, there must exist at least one index that
//    is "useful" for the proposed key.  A "useful" index is defined as follows
//    Useful Index:
//         i. contains proposedKey as a prefix
//         ii. is not a sparse index, partial index, or index with a non-simple collation
//         iii. contains no null values
//         iv. is not multikey (maybe lift this restriction later)
//         v. if a hashed index, has default seed (lift this restriction later)
//
// 3. If the proposed shard key is specified as unique, there must exist a useful,
//    unique index exactly equal to the proposedKey (not just a prefix).
//
// After validating these constraint:
//
// 4. If there is no useful index, and the collection is non-empty, we
//    must fail.
//
// 5. If the collection is empty, and it's still possible to create an index
//    on the proposed key, we go ahead and do so.