Indexes

Indexes supports the efficent execution of queries in PoloDB. Without indexes, PoloDB must begin with the first record and then read through the entire table to find the relevant records. If an appropriate index exists for a query, PoloDB can use the index to limit the number of records that must be read.

Create an index

To create an index with Rust, use create_index method:

let teachers = db.collection("teacher");
 
teachers.create_index(IndexModel {
    keys: doc! {
        "age": 1,
    },
    options: None,
})?;

This command is indicating that PoloDB will create a single field index of the age field in the teacher collection. The value of the age field represents the keys' direction in the index. It can be either 1 or -1, which means ascending or descending.

Currently, only ascending indexes are supported(which is 1).

Index name

PoloDB will generate a name for the index if you don't specify one. For example, the index name of the above example will be age_1.

Index Properties

Unique Indexes

The unique property of an index causes PoloDB to reject duplicate values for the indexed field. You can use the unique option to create a unique index.

let teachers = db.collection("teacher");
 
teachers.create_index(IndexModel {
    keys: doc! {
        "name": 1,
    },
    options: Some(IndexOptions{
        unique: Some(true),
        ..Default::default()
    }),
})?;

Drop an index

You can use the drop_index method to drop an index:

teachers.drop_index("age_1")?;