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 unset.

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

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 if both of the following conditions are fulfilled:

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

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

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

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

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

• If the upper open flag of a key range is set, 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.

The steps to convert a value to a key range with value and optional null disallowed flag are as follows:

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

2. If value is undefined or is null, then throw a “[DataError](https://www.w3.org/TR/WebIDL-1/#dataerror)“ [DOMException](https://www.w3.org/TR/WebIDL-1/#idl-DOMException) if null disallowed flag is set, or return an unbounded key range otherwise.

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

4. If key is invalid, throw a “[DataError](https://www.w3.org/TR/WebIDL-1/#dataerror)“ [DOMException](https://www.w3.org/TR/WebIDL-1/#idl-DOMException).

5. Return a key range containing only key.