indexed-struct

A Rust derive macro for creating indexed data structure with efficient query capabilities

Usage

use indexed_struct::IndexedStruct;

#[derive(IndexedStruct)]
struct Cat {
    #[indexed_struct(unique, index = "hash")]
    name: String,

    #[indexed_struct(index = "btree")]
    age: u16,

    birthday: u64,  // Not indexed
}

fn main() {
    let mut store: CatStore<usize> = CatStore::new();

    // Insert a record with primary key 1
    store.insert(1, Cat {
        name: "Fluffy".to_string(),
        age: 3,
        birthday: 1000,
    }).unwrap();

    // Query by primary key
    let cat = store.query(&1);

    // Query by indexed field
    let cat_by_name = store.query_name(&"Fluffy".to_string());

    // Query by non-unique indexed field (returns iterator)
    let cats_by_age = store.query_age(&3);
}

The generated struct will look like this:

#[derive(Default)]
struct CatStore<KeyType> {
    rows: HashMap<KeyType, Cat>,
    index_name: HashMap<String, KeyType>,
    index_age: BTreeMap<u16,HashSet<KeyType>>,
}

Macro Attributes

Struct Attributes

The IndexedStruct derive macro supports the following attributes on the struct itself:

• #[indexed_struct(name = CustomName)]: Customize the name of the generated storage struct. By default, it appends "Store" to the original struct name.
• #[indexed_struct(key_type = KeyType)]: Customize the default key type used for the primary key. By default, no default is provided and you must specify it when using the store.

Example with struct attributes:

use indexed_struct::IndexedStruct;

#[derive(IndexedStruct)]
#[indexed_struct(name = Pets, key_type = u32)]
struct Pet {
    #[indexed_struct(unique, index = "hash")]
    name: String,
    #[indexed_struct(index = "btree")]
    age: u16,
}

// This will generate a Pets<u32> struct with u32 as the default key type

Generated Methods

The macro generates various methods for efficient data access:

• insert, remove: Basic CRUD operations
• query_{field}: Query by indexed field values
• contain_{field}: Check if indexed field value exists
• update_{field}: Update specific field values
• iter_by_{field}: Iterate ordered by indexed field
• rows_by_{field}: Get rows by indexed field

Field Attributes

Index Types:

• none: No index: Linear search through all records O(n)
• hash: Hash map index for O(1) average lookup time using hashbrown HashMap
• btree: B-tree index for O(log n) lookup time with ordered iteration using std BTreeMap