version
------------------------------------------------------------------------------------------------------------------
 PostgreSQL 13.4 (Debian 13.4-1.pgdg100+1) on x86_64-pc-linux-gnu, compiled by gcc (Debian 8.3.0-6) 8.3.0, 64-bit
(1 row)

CREATE TYPE
CREATE TABLE
CREATE INDEX
INSERT 0 1000
INSERT 0 1000
INSERT 0 1000
INSERT 0 1
VACUUM
                                                                     QUERY PLAN
-----------------------------------------------------------------------------------------------------------------------------------------------------
 Index Only Scan using table_test_enum_val_idx on public.table_test_enum  (cost=0.12..4.14 rows=1 width=4) (actual time=0.014..0.016 rows=1 loops=1)
   Output: val
   Heap Fetches: 0
 Planning Time: 0.436 ms
 Execution Time: 0.048 ms
(5 rows)

PREPARE
PREPARE
PREPARE
                                                   QUERY PLAN
-----------------------------------------------------------------------------------------------------------------
 Seq Scan on public.table_test_enum  (cost=0.00..66.52 rows=1 width=4) (actual time=1.131..1.133 rows=1 loops=1)
   Output: val
   Filter: ((table_test_enum.dat IS NULL) AND (table_test_enum.val = ('Ole'::cstring)::type_table_test_enum))
   Rows Removed by Filter: 3000
 Planning Time: 0.261 ms
 Execution Time: 1.162 ms
(6 rows)

                                                                     QUERY PLAN
-----------------------------------------------------------------------------------------------------------------------------------------------------
 Index Only Scan using table_test_enum_val_idx on public.table_test_enum  (cost=0.12..4.14 rows=1 width=4) (actual time=0.023..0.026 rows=1 loops=1)
   Output: val
   Heap Fetches: 0
 Planning Time: 0.256 ms
 Execution Time: 0.054 ms
(5 rows)

                                                                     QUERY PLAN
-----------------------------------------------------------------------------------------------------------------------------------------------------
 Index Only Scan using table_test_enum_val_idx on public.table_test_enum  (cost=0.12..4.14 rows=1 width=4) (actual time=0.019..0.023 rows=1 loops=1)
   Output: val
   Heap Fetches: 0
 Planning Time: 0.259 ms
 Execution Time: 0.051 ms
(5 rows)

DEALLOCATE
DEALLOCATE
DEALLOCATE
DROP TABLE
DROP TYPE