prisma-driver-adapter-implementation

Prisma SQL Driver Adapter Implementation

Use this guide with the exact @prisma/driver-adapter-utils version installed by the target Prisma release. Driver adapters are a protocol boundary: type-compatible code can still corrupt values, leak connections, or break transactions.

When to Apply

Implementing SqlDriverAdapterFactory, SqlMigrationAwareDriverAdapterFactory, SqlDriverAdapter, or Transaction
Adding nested-transaction/savepoint support
Mapping driver values, column metadata, bind arguments, or database errors
Debugging P2039, transaction leaks, shadow-database failures, or adapter-specific query behavior

Contract snapshot

interface SqlDriverAdapterFactory extends AdapterInfo {
  connect(): Promise<SqlDriverAdapter>
}

interface SqlMigrationAwareDriverAdapterFactory extends SqlDriverAdapterFactory { connectToShadowDb(): Promise }

interface SqlDriverAdapter extends AdapterInfo { queryRaw(query: SqlQuery): Promise executeRaw(query: SqlQuery): Promise executeScript(script: string): Promise startTransaction(isolationLevel?: IsolationLevel): Promise getConnectionInfo?(): ConnectionInfo dispose(): Promise }

interface Transaction extends AdapterInfo { readonly options: { usePhantomQuery: boolean } queryRaw(query: SqlQuery): Promise executeRaw(query: SqlQuery): Promise commit(): Promise rollback(): Promise createSavepoint?(name: string): Promise rollbackToSavepoint?(name: string): Promise releaseSavepoint?(name: string): Promise }


`IsolationLevel` currently includes `READ UNCOMMITTED`, `READ COMMITTED`, `REPEATABLE READ`, `SNAPSHOT`, and `SERIALIZABLE`; validate what the concrete database supports.

## Priority rules

| Priority | Rule | Impact |
|----------|------|--------|
| CRITICAL | One dedicated connection per transaction | Prevents interleaving and leaks |
| CRITICAL | `commit`/`rollback` are lifecycle cleanup hooks | Prevents duplicate COMMIT/ROLLBACK |
| CRITICAL | Savepoints live on `Transaction`, not adapter-global depth | Makes nested scopes connection-local |
| CRITICAL | Preserve original database error code/message | Enables useful `P2039` fallback |
| HIGH | Map arguments and result metadata exactly | Prevents silent value corruption |
| HIGH | Shadow databases are isolated and always cleaned up | Makes Migrate safe |
| HIGH | Dispose only resources the adapter owns | Prevents shutting down caller-owned pools |

## Query implementation

`SqlQuery` contains `sql`, `args`, and parallel `argTypes`. Map each argument using both value and `ArgType`; do not discard type/arity information. Execute in the driver's array/tuple row mode so column order is stable.

```typescript
class ExampleQueryable {
  readonly provider = 'postgres' as const
  readonly adapterName = '@acme/adapter-example'

  constructor(protected readonly connection: DriverConnection) {}

  async queryRaw(query: SqlQuery): Promise<SqlResultSet> {
    try {
      const result = await this.connection.query({
        text: query.sql,
        values: query.args.map((value, index) =>
          mapArg(value, query.argTypes[index]),
        ),
        rowMode: 'array',
      })

      return {
        columnNames: result.fields.map((field) => field.name),
        columnTypes: result.fields.map(mapColumnType),
        rows: result.rows,
      }
    } catch (error) {
      throwAdapterError(error)
    }
  }

  async executeRaw(query: SqlQuery): Promise<number> {
    try {
      const result = await this.connection.execute(
        query.sql,
        query.args.map((value, index) => mapArg(value, query.argTypes[index])),
      )
      return result.rowsAffected ?? 0
    } catch (error) {
      throwAdapterError(error)
    }
  }
}

Result mapping

Return columnNames, columnTypes, and rows with identical lengths/order. Map driver metadata to ColumnTypeEnum deliberately:

signed integer widths to Int32/Int64; preserve 64-bit values without JS number truncation
decimal/numeric to Numeric using the representation expected by Prisma
binary to Uint8Array/Bytes
date-only, time-only, and timestamp to Date, Time, and DateTime
UUID, JSON, enum, arrays, and provider-specific unknown values to their explicit types
unsupported native types to DriverAdapterError({ kind: 'UnsupportedNativeDataType', type })

Test null, empty arrays, array element types, big integers, decimals, byte arrays, JSON, dates, and user-defined/unknown native types.

Script execution

executeScript must execute a migration script as the provider expects. Prefer the driver's native multi-statement/script facility or a real SQL parser. Naively splitting on ; breaks functions, triggers, quoted strings, and dialect-specific blocks.

Transaction protocol

startTransaction must acquire one dedicated connection, start the database transaction, apply the requested isolation level, and return a Transaction bound to that same connection. If setup fails, release it immediately.

async startTransaction(level?: IsolationLevel): Promise<Transaction> {
  const connection = await this.pool.acquire()
  try {
    const tx = new ExampleTransaction(connection, () => connection.release())
    await tx.executeRaw({ sql: 'BEGIN', args: [], argTypes: [] })
    if (level) {
      await tx.executeRaw({
        sql: `SET TRANSACTION ISOLATION LEVEL ${validateLevel(level)}`,
        args: [],
        argTypes: [],
      })
    }
    return tx
  } catch (error) {
    connection.release(error)
    throwAdapterError(error)
  }
}

Commit and rollback

Prisma coordinates the SQL COMMIT/ROLLBACK through executeRaw. The transaction object's commit() and rollback() methods are lifecycle hooks: detach listeners and release the dedicated connection exactly once. They must not issue a second SQL commit/rollback.

class ExampleTransaction extends ExampleQueryable implements Transaction {
  readonly options = { usePhantomQuery: false }
  #closed = false

  constructor(connection: DriverConnection, private readonly release: () => void) {
    super(connection)
  }

  async commit() { this.finish() }
  async rollback() { this.finish() }

  private finish() {
    if (this.#closed) return
    this.#closed = true
    this.release()
  }

  async createSavepoint(name: string) {
    await this.control(`SAVEPOINT ${safeSavepoint(name)}`)
  }

  async rollbackToSavepoint(name: string) {
    await this.control(`ROLLBACK TO SAVEPOINT ${safeSavepoint(name)}`)
  }

  async releaseSavepoint(name: string) {
    await this.control(`RELEASE SAVEPOINT ${safeSavepoint(name)}`)
  }

  private async control(sql: string) {
    await this.executeRaw({ sql, args: [], argTypes: [] })
  }
}

Implement the optional savepoint methods only where the provider supports them. Validate/quote savepoint identifiers. For providers whose savepoints are intentionally no-ops, document and test that limitation.

Never keep transaction depth on the shared adapter. Parallel transactions make adapter-global depth incorrect; nested state belongs to the returned transaction connection and Prisma's savepoint calls.

Error mapping

Wrap recognized driver failures in DriverAdapterError. Map known conditions to MappedError kinds such as constraint violations, authentication/reachability, missing table/column/database, timeouts, closed transactions, invalid input, value range, and write conflicts.

For database errors, preserve originalCode and originalMessage even when falling back to the provider-specific raw variant:

import {
  DriverAdapterError,
  type Error as DriverAdapterErrorObject,
  type MappedError,
} from '@prisma/driver-adapter-utils'

function convertDriverError(error: DatabaseError): DriverAdapterErrorObject {
  return {
    originalCode: String(error.code),
    originalMessage: error.message,
    ...mapKnownOrRaw(error),
  }
}

function mapKnownOrRaw(error: DatabaseError): MappedError {
  if (error.code === '23505') {
    return { kind: 'UniqueConstraintViolation', constraint: parsedConstraint(error) }
  }
  return {
    kind: 'postgres',
    code: String(error.code ?? 'N/A'),
    severity: error.severity ?? 'N/A',
    message: error.message,
    detail: error.detail,
    column: error.column,
    hint: error.hint,
  }
}

function throwAdapterError(error: unknown): never {
  if (!isDatabaseError(error)) throw error
  throw new DriverAdapterError(convertDriverError(error))
}

Prisma uses preserved original details when an unmapped driver error becomes P2039. Do not replace every unknown exception with a fabricated GenericJs id; rethrow genuinely unexpected non-driver errors so programming bugs remain visible.

Factory, ownership, and shadow database

connect() returns a fresh usable adapter connection/pool wrapper.
Track whether the factory created the pool. dispose() closes owned pools and only detaches listeners from caller-owned pools unless an explicit option transfers ownership.
Implement SqlMigrationAwareDriverAdapterFactory only when connectToShadowDb() can create an isolated shadow database, connect to it, and drop it during disposal/failure cleanup.
Never point the shadow adapter at the primary database. Quote generated identifiers and use cryptographically unique names.
getConnectionInfo() should accurately report schemaName, maxBindValues when applicable, and supportsRelationJoins.

Verification checklist

Typecheck against the exact target @prisma/driver-adapter-utils version
queryRaw preserves column order, types, nulls, and precision
executeRaw reports affected rows correctly
executeScript handles provider-specific multi-statement syntax
Concurrent interactive transactions use distinct dedicated connections
Success commits and releases once; failure rolls back and releases once
Nested transaction tests exercise create/rollback/release savepoint hooks
Unsupported isolation levels fail as InvalidIsolationLevel
Known constraints map to structured errors
Unmapped database errors retain original code/message and surface useful P2039
Dispose ownership is tested for internal and external pools
Shadow database creation, use, failure cleanup, and disposal are isolated
Run Prisma Client integration/E2E tests, not only adapter unit tests

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