Prisma: prepared statement "s0" already exists

What it means in plain English

Prisma uses named prepared statements. PgBouncer, and Supabase's Supavisor pooler, do not always keep those statements on the same connection. Prisma's PgBouncer guide shows this error when Migrate runs through the pooler:

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

Likely causes

• DATABASE_URL is the pooled Supabase string (often port 6543), and prisma migrate or prisma db push uses it.
• The runtime client and the CLI share one URL.
• ?pgbouncer=true is missing on an older pooler, or it was added to the direct URL as well.

How to fix it, step by step

1. Keep two URLs. Prisma's example is DATABASE_URL for the pooler, with ?pgbouncer=true, and DIRECT_URL for a direct Postgres connection.
2. Point Prisma CLI at the direct URL in prisma.config.ts (datasource.url). Prisma says Migrate does not support going through PgBouncer, and CLI commands should use that direct string.
3. Point Prisma Client at the pooled URL through the driver adapter. Prisma's Supabase note says Supavisor behaves like PgBouncer and that you can add ?pgbouncer=true to the pooled string from the Supabase database settings.
4. For a PgBouncer at version 1.21.0 or newer, Prisma says you generally do not need pgbouncer=true, and that the pooler should be in transaction mode. The "s0 already exists" error on Migrate is still fixed by using the direct URL for CLI commands.

How to check it worked

• prisma migrate deploy or prisma db push completes using the direct host.
• The running app still connects with the pooled host, and the s0 error is gone from the deploy log.

Sources

• https://www.prisma.io/docs/orm/prisma-client/setup-and-configuration/databases-connections/pgbouncer (opens in a new tab)