PG16 - Add reindex database/system tests (#7167)

In PG16, REINDEX DATABASE/SYSTEM name is optional.
We already don't propagate these commands automatically.
Testing here with run_command_on_workers.

Relevant PG commit:
https://github.com/postgres/postgres/commit/2cbc3c1

src/test/regress/expected/pg16.out

@@ -916,6 +916,28 @@ SELECT result FROM run_command_on_workers
  REINDEX
 (2 rows)
 
+-- REINDEX DATABASE/SYSTEM name is optional
+-- We already don't propagate these commands automatically
+-- Testing here with run_command_on_workers
+-- Relevant PG commit: https://github.com/postgres/postgres/commit/2cbc3c1
+REINDEX DATABASE;
+SELECT result FROM run_command_on_workers
+($$REINDEX DATABASE$$);
+ result
+---------------------------------------------------------------------
+ REINDEX
+ REINDEX
+(2 rows)
+
+REINDEX SYSTEM;
+SELECT result FROM run_command_on_workers
+($$REINDEX SYSTEM$$);
+ result
+---------------------------------------------------------------------
+ REINDEX
+ REINDEX
+(2 rows)
+
 --
 -- random_normal() to provide normally-distributed random numbers
 -- adding here the same tests as the ones with random() in aggregate_support.sql

src/test/regress/sql/pg16.sql

@@ -530,6 +530,19 @@ REINDEX SYSTEM;
 SELECT result FROM run_command_on_workers
 ($$REINDEX SYSTEM$$);
 
+-- REINDEX DATABASE/SYSTEM name is optional
+-- We already don't propagate these commands automatically
+-- Testing here with run_command_on_workers
+-- Relevant PG commit: https://github.com/postgres/postgres/commit/2cbc3c1
+
+REINDEX DATABASE;
+SELECT result FROM run_command_on_workers
+($$REINDEX DATABASE$$);
+
+REINDEX SYSTEM;
+SELECT result FROM run_command_on_workers
+($$REINDEX SYSTEM$$);
+
 --
 -- random_normal() to provide normally-distributed random numbers
 -- adding here the same tests as the ones with random() in aggregate_support.sql