> For the complete documentation index, see [llms.txt](https://docs.lingoql.com/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.lingoql.com/sub0/creating-database-models/indexing.md).

# Indexing

Sub0 uses declarative indexing. Set `indexable` or `fts` on a field, and Sub0 handles the database-specific index behavior.

***

### Standard indexes

To create a standard database index on a field, set `indexable` to `true`.

```json
{
  "email": {
    "type": "String",
    "indexable": true
  }
}
```

* Improves lookup performance for equality and range queries
* Supported across MongoDB, MySQL/MariaDB, and PostgreSQL
* Indexes are created automatically during model provisioning

***

### Full-text search

To enable full-text search on a field, set `fts` to `true`.

```json
{
  "content": {
    "type": "String",
    "fts": true
  }
}
```

* Enables text search across large string fields
* Optimized per database engine
* Can be combined with `indexable` when appropriate

***

### Combine indexing options

A field can be both indexed and searchable:

```json
{
  "title": {
    "type": "String",
    "indexable": true,
    "fts": true
  }
}
```

Use this for fields that are:

* Frequently filtered
* Frequently searched
* Central to query performance

***

### Index nested fields

Indexes can be applied to fields inside `JSON_OBJECT` structures.

```json
{
  "profile": {
    "type": "JSON_OBJECT",
    "properties": {
      "username": {
        "type": "String",
        "indexable": true
      }
    }
  }
}
```

Nested indexing behavior is handled automatically by Sub0.

***

### What Sub0 handles automatically

* Index creation and updates
* Database-specific index syntax
* Compatibility across supported databases
* Safe index application during provisioning

***

### Best practices

* Index fields used in filters, joins, or lookups
* Avoid indexing fields that are rarely queried or constantly updated unless necessary
* Use `fts` only for meaningful text search use cases

***

### Summary

* Use `indexable` for standard indexes
* Use `fts` for full-text search
* Declare indexes once — Sub0 handles the rest

Next, see [Anatomy of Models](/sub0/creating-database-models/anatomy-of-models.md) for the full field property reference.


---

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