In IndexedDB, indexes provide a way to efficiently query and retrieve data based on specific keys or ranges of keys within an object store. They are similar to indexes in relational databases, allowing for faster data access by pre-sorting and organizing data based on specified criteria.
Here's a breakdown of the concept of indexes in IndexedDB :* Efficient Data Retrieval : Indexes improve the performance of data retrieval operations by creating a sorted data structure based on specific keys or properties of the stored objects. This allows for faster lookups, especially when searching for data by keys other than the primary key.
* Creating Indexes : Indexes are created on specific properties or keys of objects within an object store. When creating an index, developers specify the name of the index, the key path (property) to index, and optionally, whether the index should enforce uniqueness for the indexed values.
* Types of Indexes : IndexedDB supports two types of indexes:
* Single-Entry Indexes : These indexes map each unique key or property value to one or more corresponding records. They are useful for ensuring uniqueness or performing exact-match queries.
* Multi-Entry Indexes : These indexes allow multiple records to be associated with the same index key or property value. They are useful for querying data based on ranges, partial matches, or for properties with array values.
Usage : Once created, indexes can be used to perform efficient queries and data retrieval operations within the object store. Queries using indexes can be performed using methods such as
get(), getAll(), getAllKeys(), openCursor(), and
openKeyCursor().
* Transaction Scope : Like other operations in IndexedDB, index operations are performed within the scope of a transaction. This ensures that index updates are atomic and consistent with other database operations.
* Updating Indexes : Indexes are automatically updated whenever data within the associated object store is added, modified, or deleted. IndexedDB handles index updates transparently, ensuring that indexes remain consistent with the underlying data.
