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What are the keys and indexes

FindEntity and FindEntities methods can be used to search any row(s) with any condition(s). But they are slow, because they iterate the rows one by one. To address this problem keys and indexes were introduced.

  1. A key consists of 1-n fields and can be used to look up row(s) quickly. It also can be used in rows validation
  2. An index has a reference to a single field and can be used for effective range scan
Different row(s) retrieval methods efficiency comparison
Method Underlying structure Time complexity Comments
meta.GetEntity(int index)
Retrieve a single row using provided physical row's index
 list O(1) fastest method
meta.GetEntity(BGId Id)
Retrieve a single row using provided row's ID
 hashtable O(1)
GetEntity(string name)
Retrieve a single row using provided row's name
 hashtable O(1)
key.GetEntityByKey(params object[] keys)
key.GetEntitiesByKey(params object[] keys)
Retrieve a first row/all rows with provided keys values
 hashtable O(1)
index.FindEntitiesByIndex(indexOperator)
Retrieve all rows with index field value within provided range
 b-tree O(log n) if index field data is not skewed
meta.FindEntity(predicate)
meta.FindEntities(predicate)
Retrieve a first row/all rows using provided filter (any conditions supported)
 N/A O(n), full-scan
Keys

Following fields can be added to a key: bool, int, long, decimal, bool?, int?, long?, string, text, enum, relationSingle.

You can access the matching row(s) directly without searching, using BGKey class. Available options:

  1. Use generated methods (recommended)
  2. Use basic API. To access the key, use BGMetaEntity.GetKey({keyName}) method. To get a row(s), use BGKey.GetEntityByKey or BGKey.GetEntitiesByKey methods
  3. If you use Visual Scripting assets, you can use generated unit/node if it's supported

Keys make row(s) access faster, but uses extra memory and may slow down write (update) operations, so do not use keys for data, which is updated frequently.

Indexes

Indexes enables row(s) range scan fast operations, but uses extra memory and may slow down write (update) operations. Currently only single field index is supported. Available options to use an index:

  1. Use generated methods (recommended)
  2. Use basic API. To access the index use BGMetaEntity.GetIndex({indexName}) method. To query rows use index.FindEntitiesByIndex method

Indexes also provide methods for finding max/min values. Obtain a reference to an index (via generated property _{IndexName}) and call GetMax/GetMin methods

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