# Supported database features (/docs/orm/contract-authoring/capabilities)

The contract records which database features your packages support, so Prisma ORM can reject an unsupported one early with a clear error.

Location: ORM > Contract authoring > Supported database features

Your [contract](/guides/contract-authoring-the-data-contract), the `contract.prisma` file that replaced `schema.prisma`, describes your data. [`npx prisma contract emit`](/guides/orm-contract-emit) writes `contract.json` and `contract.d.ts` beside it. The `capabilities` section of `contract.json` lists the database features you can use, under keys such as `sql.lateral`. Prisma ORM writes that section, and you never edit it. If you use a feature that is not listed, Prisma ORM raises an error instead of sending the query to the database.

## Where the `capabilities` section comes from

The keys come from your database package (`@prisma/orm-postgres`, `@prisma/orm-sqlite`, or `@prisma/orm-mongo`) and any extension packages listed in `prisma.config.ts`. `npx prisma contract emit` never connects to your database: it reads those packages and writes what they report, in groups:

```json title="src/prisma/contract.json (excerpt)"
{
  "capabilities": {
    "postgres": { "distinctOn": true, "pgvector.cosine": true },
    "sql": { "lateral": true, "scalarList": true }
  }
}
```

Error messages and the table below name a key group first, `postgres.pgvector.cosine`. The `sql` group holds keys that more than one SQL database may support, and SQLite reports `false` for some of them. Keys under `postgres` belong to PostgreSQL only. Extension packages add keys of their own, and `pgvector.cosine` comes from the pgvector package. Install it with `npm install @prisma/orm-extension-pgvector`, list it in `prisma.config.ts`, and run `npx prisma contract emit` again:

```typescript title="prisma.config.ts"
import "dotenv/config";
import { definePrismaConfig } from "prisma/config";
import pgvector from "@prisma/orm-extension-pgvector/control";
import { defineConfig as ormConfig } from "@prisma/orm-postgres/config";

export default definePrismaConfig({
  orm: ormConfig({
    contract: "./src/prisma/contract.prisma",
    extensions: [pgvector],
    db: { connection: process.env['DATABASE_URL']! },
  }),
});
```

pgvector is also a PostgreSQL server extension, and the package ships a migration that installs it. Apply it with `npx prisma db migrate`, see [Using extensions](/guides/extensions-using-extensions). Run `npx prisma contract emit` after every change to the contract or to the extension list.

## What the `capabilities` section controls

**When the contract is built.** If your contract uses a feature your database package does not support, `npx prisma contract emit` fails. SQLite has no `scalarList` key, so a list field such as `tags String[]` fails on SQLite:

```text
Field "User.tags" is a scalar list, but target "sqlite" does not support
scalar lists (the adapter does not report the "scalarList" capability).
Remove the list or author it against a target that supports scalar lists.
```

In that message, both words mean your database package, and the message's `"scalarList"` is the `sql.scalarList` key. Do one of the two: remove the list field, or move to a database that supports list fields. To move to PostgreSQL, change the `@prisma/orm-sqlite/config` import and the connection string in `prisma.config.ts`, and create the new database.

**When you call a method on the [SQL query builder](/guides/reference-2-reference-sql-query-builder) or on the ORM client.** A method that needs a feature throws an error whose `code` is `ORM.CAPABILITY_MISSING`, and the message names the method and the key:

```text
distinctOn() requires capability postgres.distinctOn
```

That message means the method is not available on the database package you chose, so rewrite the query without it, or move to a database that supports the feature. If the key comes from an extension package, install that package and list it in `prisma.config.ts`. You do not have to run the query to get the error, so a test that only builds the query still fails. Your own code can read the same list through `db`, the client you create once in `src/prisma/db.ts`, which `npx prisma orm init` writes. A value such as `db.contract.capabilities.sql?.lateral` is `true` or `false`, or `undefined` if the whole group is missing. For a key with a dot in it, write `db.contract.capabilities.postgres?.["pgvector.cosine"]`:

```typescript
if (db.contract.capabilities.sql?.lateral) {
  // run the lateral join here, or fall back to a second query
}
```

## Example keys

A few of the keys your database package and extension packages supply:

| Key                        | What it covers                            |
| -------------------------- | ----------------------------------------- |
| `sql.lateral`              | Lateral joins (`lateralJoin()`)           |
| `sql.returning`            | `RETURNING` clauses on writes             |
| `sql.scalarList`           | List fields such as `tags String[]`       |
| `postgres.distinctOn`      | `DISTINCT ON` queries (`distinctOn()`)    |
| `postgres.pgvector.cosine` | Cosine distance from the pgvector package |

PostgreSQL reports `true` for all three `sql` keys above, while SQLite reports `false` for `sql.lateral`, `true` for `sql.returning`, and has no `sql.scalarList` key at all. This table is a sample, not the full list, so open `src/prisma/contract.json` in your project to see every key you have. The MongoDB packages report no keys, so neither check applies on MongoDB. The [ORM reference](/guides/reference-2-reference) lists the methods each database has.

## The `capabilities` section and `prisma db verify`

[`npx prisma db verify`](/guides/orm-db-verify) checks the live database against the contract's tables and columns, not against this section: the keys say what your packages support, recorded when you run `npx prisma contract emit`.

## Prompt your coding agent

Projects created with `npm create prisma@latest` include the [Prisma ORM skills](/guides/tools-skills#available-skills-for-prisma-orm-8) for your coding agent. In an existing project, run `npx prisma skills sync` to add them. The `prisma-8` skill covers this material, so ask your agent to:

- "Which keys in the `capabilities` section does our code rely on, and which package provides each?"
- "Add pgvector to the project and confirm its key shows up in the emitted contract."

## Next steps

- See where the `capabilities` block is, and what `contract.d.ts` holds, in [contract.json and contract.d.ts](/guides/contract-authoring-the-contract-artifact).
- Add extension packages, and the keys they bring, in the [CLI configuration](/guides/introduction-6-configuration).

## Related pages

- [`Author in PSL`](/guides/contract-authoring-psl-syntax): Write the Prisma ORM contract in the Prisma schema language you already know, plus the Prisma ORM 8 additions.
- [`Author in TypeScript`](/guides/contract-authoring-typescript-schema-builder): Define the Prisma ORM contract with a typed builder in TypeScript instead of a schema file. Same models, same `contract.json` and `contract.d.ts`, no separate language.
- [`contract.json and contract.d.ts`](/guides/contract-authoring-the-contract-artifact): contract.json and contract.d.ts are the two files every other part of Prisma ORM reads. Here is what is inside them.
- [`Editor support`](/guides/contract-authoring-editor-support): What the Prisma VS Code extension does for a Prisma ORM contract, and what to do when it stops accepting the file.
- [`The data contract`](/guides/contract-authoring-the-data-contract): The data contract is the one description of your data model and how it is stored. Prisma ORM types your queries, plans your migrations, and checks your database against it.

## Related pages

- [Authentication & Tools](./authentication-tools-index.md)
- [Build](./build-index.md)
- [Changelog](../changelog.md)
- [Concepts](./concepts-index.md)
- [Console commands](./console-commands-index.md)
- [Contract Authoring](./contract-authoring-index.md)
- [Core Concepts](./core-concepts-index.md)
- [Data Modeling](./data-modeling-index.md)
- [Database](./database-index.md)
- [DB commands](./db-commands-index.md)

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