`client`: Add methods to Prisma Client

info

Prisma Client extensions are Generally Available from versions 4.16.0 and later. They were introduced in Preview in version 4.7.0. Make sure you enable the clientExtensions Preview feature flag if you are running on a version earlier than 4.16.0.

You can use the client Prisma Client extensions component to add top-level methods to Prisma Client.

Extend Prisma Client

Use the $extends client-level method to create an extended client. An extended client is a variant of the standard Prisma Client that is wrapped by one or more extensions. Use the client extension component to add top-level methods to Prisma Client.

To add a top-level method to Prisma Client, use the following structure:

const prisma = new PrismaClient().$extends({
  client?: { ... }
})

Example

The following example uses the client component to add two methods to Prisma Client:

• $log outputs a message.
• $totalQueries returns the number of queries executed by the current client instance. It uses the metrics feature to collect this information.

info

To use metrics in your project, you must enable the metrics feature flag in the generator block of your schema.prisma file. Learn more.

const prisma = new PrismaClient().$extends({
  client: {
    $log: (s: string) => console.log(s),
    async $totalQueries() {
      const index_prisma_client_queries_total = 0
      // Prisma.getExtensionContext(this) in the following block
      // returns the current client instance
      const metricsCounters = await (
        await Prisma.getExtensionContext(this).$metrics.json()
      ).counters

      return metricsCounters[index_prisma_client_queries_total].value
    },
  },
})

async function main() {
  prisma.$log('Hello world')
  const totalQueries = await prisma.$totalQueries()
  console.log(totalQueries)
}