How to fix Prepared statement does not exist in PostgreSQL

Understanding Prepared Statement Lifecycle: When you prepare a statement in PostgreSQL, it is stored on that specific server connection with a name (S_1, S_2, etc.) or as an unnamed statement. The connection pooler's role is critical—in transaction mode, PgBouncer acts as a multiplexer, sending multiple logical transactions across fewer physical connections. When a transaction ends, PgBouncer sends RESET ALL to reset the physical connection, which deallocates all prepared statements. Your application driver, however, may cache the statement name expecting to reuse it on what it thinks is the same connection. The next transaction through the pooler gets a different physical connection or the same one after reset, and the statement no longer exists.

Prepared Statement Protocol Details: PostgreSQL supports two parameter passing methods: text and binary. Connection poolers like PgBouncer may have issues with binary protocol handling due to buffering differences. The error "caused by pgbouncer being upset over the use of plaintext parameters to prepared statements" suggests Pgbouncer has stricter validation in some configurations.

Alternatives to Prepared Statements: If disabling prepared statements causes performance concerns, consider: (1) using connection pooling directly in your application rather than PgBouncer, (2) using a different pooling strategy like PgPool with more forgiving prepared statement handling, or (3) caching query results in application memory instead of relying on server-side prepared statements. For most applications not executing thousands of queries per second, the performance difference is negligible.