If you are using pg_bouncer, you can refer to this document:

The reuse of prepared statements has one downside. If the return or argument types of a prepared statement changes across executions then PostgreSQL currently throws an error such as:

ERROR: cached plan must not change result type You can avoid such errors by not having multiple clients that use the exact same query string in a prepared statement, but expecting different argument or result types. One of the most common ways of running into this issue is during a DDL migration where you add a new column or change a column type on an existing table. In those cases you can run RECONNECT on the PgBouncer admin console after doing the migration to force a re-prepare of the query and make the error go away.