2.9. Key range

Records can be retrieved from object stores and indexes using either keys or key ranges. A key range is a continuous interval over some data type used for keys.

A key range has an associated lower bound (null or a key).

A key range has an associated upper bound (null or a key).

A key range has an associated lower open flag. Unless otherwise stated it is false.

A key range has an associated upper open flag. Unless otherwise stated it is false.

A key range may have a lower bound equal to its upper bound. A key range must not have a lower bound greater than its upper bound.

A key range containing only key has both lower bound and upper bound equal to key.

A key is in a key range range if both of the following conditions are fulfilled:

• The range’s lower bound is null, or it is less than key, or it is both equal to key and the range’s lower open flag is false.

• The range’s upper bound is null, or it is greater than key, or it is both equal to key and the range’s upper open flag is false.

• If a key range‘s lower open flag is false, the lower bound key of the key range is included in the range itself.

• If a key range‘s lower open flag is true, the lower bound key of the key range is excluded from the range itself.

• If a key range‘s upper open flag is false, the upper bound key of the key range is included in the range itself.

• If a key range‘s upper open flag is true, the upper bound key of the key range is excluded from the range itself.

An unbounded key range is a key range that has both lower bound and upper bound equal to null. All keys are in an unbounded key range.

To convert a value to a key range with value and optional null disallowed flag, run these steps:

1. If value is a key range, return value.

2. If value is undefined or is null, then throw a “[DataError](https://heycam.github.io/webidl/#dataerror)“ [DOMException](https://heycam.github.io/webidl/#idl-DOMException) if null disallowed flag is true, or return an unbounded key range otherwise.

3. Let key be the result of running convert a value to a key with value. Rethrow any exceptions.

4. If key is invalid, throw a “[DataError](https://heycam.github.io/webidl/#dataerror)“ [DOMException](https://heycam.github.io/webidl/#idl-DOMException).

5. Return a key range containing only key.