## PostgreSQL 18.3

CREATE TABLE t(c1 int,c2 int);

postgres=# EXPLAIN(VERBOSE) SELECT c1, c2 FROM t ORDER BY c1,c2;
QUERY PLAN
------------------------------------------------------------------
Sort (cost=158.51..164.16 rows=2260 width=8)
Output: c1, c2
Sort Key: t.c1, t.c2
-> Seq Scan on public.t (cost=0.00..32.60 rows=2260 width=8)
Output: c1, c2
Query Identifier: -4675081474881745094
(6 rows)

postgres=# EXPLAIN(VERBOSE) SELECT c2, c1 FROM t ORDER BY c1,c2;
QUERY PLAN
------------------------------------------------------------------
Sort (cost=158.51..164.16 rows=2260 width=8)
Output: c2, c1
Sort Key: t.c1, t.c2
-> Seq Scan on public.t (cost=0.00..32.60 rows=2260 width=8)
Output: c2, c1
Query Identifier: -3269814016130981549
(6 rows)

postgres=# EXPLAIN(VERBOSE) SELECT c1 FROM t ORDER BY c1,c2;
QUERY PLAN
------------------------------------------------------------------
Sort (cost=158.51..164.16 rows=2260 width=8)
Output: c1, c2
Sort Key: t.c1, t.c2
-> Seq Scan on public.t (cost=0.00..32.60 rows=2260 width=8)
Output: c1, c2
Query Identifier: -4675081474881745094
(6 rows)

postgres=# EXPLAIN(VERBOSE) SELECT c2 FROM t ORDER BY c1,c2;
QUERY PLAN
------------------------------------------------------------------
Sort (cost=158.51..164.16 rows=2260 width=8)
Output: c2, c1
Sort Key: t.c1, t.c2
-> Seq Scan on public.t (cost=0.00..32.60 rows=2260 width=8)
Output: c2, c1
Query Identifier: -3269814016130981549
(6 rows)

## PostreSQL 19dev(d841ca2d149666b8) with Patch

CREATE TABLE t(c1 int,c2 int);

postgres=# EXPLAIN(VERBOSE) SELECT c1, c2 FROM t ORDER BY c1,c2;
QUERY PLAN
------------------------------------------------------------------
Sort (cost=158.51..164.16 rows=2260 width=8)
Output: c1, c2
Sort Key: t.c1, t.c2
-> Seq Scan on public.t (cost=0.00..32.60 rows=2260 width=8)
Output: c1, c2
Query Identifier: 3650220897747797500
(6 rows)

postgres=# EXPLAIN(VERBOSE) SELECT c2, c1 FROM t ORDER BY c1,c2;
QUERY PLAN
------------------------------------------------------------------
Sort (cost=158.51..164.16 rows=2260 width=8)
Output: c2, c1
Sort Key: t.c1, t.c2
-> Seq Scan on public.t (cost=0.00..32.60 rows=2260 width=8)
Output: c2, c1
Query Identifier: -3038222286574995023
(6 rows)

postgres=# EXPLAIN(VERBOSE) SELECT c1 FROM t ORDER BY c1,c2;
QUERY PLAN
------------------------------------------------------------------
Sort (cost=158.51..164.16 rows=2260 width=8)
Output: c1, c2
Sort Key: t.c1, t.c2
-> Seq Scan on public.t (cost=0.00..32.60 rows=2260 width=8)
Output: c1, c2
Query Identifier: -8371868852328991336
(6 rows)

postgres=# EXPLAIN(VERBOSE) SELECT c2 FROM t ORDER BY c1,c2;
QUERY PLAN
------------------------------------------------------------------
Sort (cost=158.51..164.16 rows=2260 width=8)
Output: c2, c1
Sort Key: t.c1, t.c2
-> Seq Scan on public.t (cost=0.00..32.60 rows=2260 width=8)
Output: c2, c1
Query Identifier: -8689818593596346321
(6 rows)