Indexed Database API

This document defines APIs for a database of records holding simple values and hierarchical objects. Each record consists of a key and some value. Moreover, the database maintains indexes over records it stores. An application developer directly uses an API to locate records either by their key or by using an index. A query language can be layered on this API. An indexed database can be implemented using a persistent B-tree data structure.

Indexed Database API

Introduction

User agents need to store large numbers of objects locally in order to satisfy off-line data requirements of Web applications. [[WEBSTORAGE]] is useful for storing pairs of keys and their corresponding values. However, it does not provide in-order retrieval of keys, efficient searching over values, or storage of duplicate values for a key.

This specification provides a concrete API to perform advanced key-value data management that is at the heart of most sophisticated query processors. It does so by using transactional databases to store keys and their corresponding values (one or more per key), and providing a means of traversing keys in a deterministic order. This is often implemented through the use of persistent B-tree data structures that are considered efficient for insertion and deletion as well as in-order traversal of very large numbers of data records.

TODO: Add examples using the sync and the async APIs.

This specification defines one class of products:

Conforming user agent

A user agent MUST behave as described in this specification in order to be considered conformant.

User agents MAY implement algorithms given in this specification in any way desired, so long as the end result is indistinguishable from the result that would be obtained by the specification's algorithms.

A conforming Indexed Database API user agent MUST also be a conforming implementation of the IDL fragments of this specification, as described in the “Web IDL” specification. [[!WEBIDL]]

This specification uses both the terms "conforming user agent(s)" and "user agent(s)" to refer to this product class.

Dependencies

This specification relies on several other underlying specifications.

DOM-LEVEL-3-EVENTS: The terms default action and propagation path are defined by the Document Object Model (DOM) Level 3 Events Specification [[!DOM-LEVEL-3-EVENTS]].
HTML5: The terms and algorithms document base URL, event handler attributes, event handler event type, Function, origin, same origin, structured clone, structured clone algorithm, task, task source, and queue a task are defined by the HTML 5 specification [[!HTML5]].
WebIDL: Many of the interface definitions and all of the IDL in this spec depends on [[!WEBIDL]].
WebWorkers: The term Worker is defined by the WebWorkers specification [[!WEBWORKERS]].