postgres=# create extension pg_duckdb;
WARNING:  To actually execute queries using DuckDB you need to run "SET duckdb.execution TO true;"
CREATE EXTENSION
postgres=# SET duckdb.execution TO true;
SET
postgres=# SELECT COUNT(*) FROM t;
 count 
-------
  1000
(1 row)

postgres=# PREPARE test_stmt AS SELECT COUNT(*) FROM t;
PREPARE
postgres=# EXECUTE test_stmt;
 count 
-------
     0
(1 row)