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Configure Prisma Client with PgBouncer

An external connection pooler like PgBouncer holds a connection pool to the database, and proxies incoming client connections by sitting between Prisma Client and the database. This reduces the number of processes a database has to handle at any given time.

Usually, this works transparently, but some connection poolers only support a limited set of functionality. One common feature that external connection poolers do not support are named prepared statements, which Prisma ORM uses. For these cases, Prisma ORM can be configured to behave differently.

PgBouncer​

Set PgBouncer to transaction mode​

For Prisma Client to work reliably, PgBouncer must run in Transaction mode.

Transaction mode offers a connection for every transaction – a requirement for the Prisma Client to work with PgBouncer.

Add pgbouncer=true for PgBouncer versions below 1.21.0​

warning

We recommend not setting pgbouncer=true in the database connection string if you're using PgBouncer 1.21.0 or later.

To use Prisma Client with PgBouncer, add the ?pgbouncer=true flag to the PostgreSQL connection URL:

postgresql://USER:PASSWORD@HOST:PORT/DATABASE?pgbouncer=true
info

PORT specified for PgBouncer pooling is sometimes different from the default 5432 port. Check your database provider docs for the correct port number.

Configure max_prepared_statements in PgBouncer to be greater than zero​

Prisma uses prepared statements, and setting max_prepared_statements to a value greater than 0 enables PgBouncer to use those prepared statements.

info

PORT specified for PgBouncer pooling is sometimes different from the default 5432 port. Check your database provider docs for the correct port number.

Prisma Migrate and PgBouncer workaround​

Prisma Migrate uses database transactions to check out the current state of the database and the migrations table. However, the Schema Engine is designed to use a single connection to the database, and does not support connection pooling with PgBouncer. If you attempt to run Prisma Migrate commands in any environment that uses PgBouncer for connection pooling, you might see the following error:

Error: undefined: Database error
Error querying the database: db error: ERROR: prepared statement "s0" already exists

To work around this issue, you must connect directly to the database rather than going through PgBouncer. To achieve this, you can use the directUrl field in your datasource block.

For example, consider the following datasource block:

datasource db {
  provider  = "postgresql"
  url       = "postgres://USER:PASSWORD@HOST:PORT/DATABASE?pgbouncer=true"
  directUrl = "postgres://USER:PASSWORD@HOST:PORT/DATABASE"
}

The block above uses a PgBouncer connection string as the primary URL using url, allowing Prisma Client to take advantage of the PgBouncer connection pooler.

It also provides a connection string directly to the database, without PgBouncer, using the directUrl field. This connection string will be used when commands that require a single connection to the database, such as prisma migrate dev or prisma db push, are invoked.

PgBouncer with different database providers​

There are sometimes minor differences in how to connect directly to a Postgres database that depend on the provider hosting the database.

Below are links to information on how to set up these connections with providers who have setup steps not covered here in our documentation:

Supabase Supavisor​

Supabase's Supavisor behaves similarly to PgBouncer. You can add ?pgbouncer=true to your connection pooled connection string available via your Supabase database settings.

Other external connection poolers​

Although Prisma ORM does not have explicit support for other connection poolers, if the limitations are similar to the ones of PgBouncer you can usually also use pgbouncer=true in your connection string to put Prisma ORM in a mode that works with them as well.