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// SPDX-FileCopyrightText: 2021 Lutris Engineering, Inc
// SPDX-License-Identifier: BlueOak-1.0.0 OR BSD-2-Clause-Patent
// SPDX-FileContributor: Piper McCorkle <piper@lutris.engineering>
/**
The four indices used in the underlying data store. The names refer
to the serialization order, and by extension the sort order.
These indices are the same as are used in Datomic, and are described
in [Datomic's documentation] in great detail.
[Datomic's documentation]: https://docs.datomic.com/on-prem/query/indexes.html
*/
#[derive(Clone, Copy, Debug, PartialEq)]
pub enum Index {
/**
Entity-Attribute-Value-T index
Provides information on an entity-by-entity basis.
*/
EAVT,
/**
Attribute-Entity-Value-T index
Provides access to all instances of each attribute.
*/
AEVT,
/**
Attribute-Value-Entity-T index
Provides efficient access to unique entities
*/
AVET,
/**
Value-Attribute-Entity-T index
Also known as the reverse index. Provides relationship access in
reverse. For example, if a page has its owner as an attribute
but not vice versa, this index allows a query to walk backwards
from owner to page.
*/
VAET,
}
impl Index {
/// Map the [Index] to its byte representation
pub const fn byte(&self) -> u8 {
match self {
Self::EAVT => 0,
Self::AEVT => 1,
Self::AVET => 2,
Self::VAET => 3,
}
}
/// Map byte representation to an [Index]
pub fn from_byte(b: u8) -> Self {
match b {
0 => Self::EAVT,
1 => Self::AEVT,
2 => Self::AVET,
3 => Self::VAET,
_ => panic!("invalid index"),
}
}
}