Improve cleanup phases in regression tests of pg_stat_statements

As shaped, two DROP ROLE queries included in "user_activity" were
showing in the reports for "wal".  The intention is to keep each test
isolated and independent, so this is incorrect.  This commit adds some
calls to pg_stat_statements_reset() to clean up the statistics once each
test finishes, so as there are no risks of overlap in the reports for
individial scenarios.

The addition in "user_activity" fixes the output of "wal".  The new
resets done in "level_tracking" and "utility" are added for consistency
with the rest, though they do not affect the stats generated in the
other tests.

Oversight in d0028e3.

Reported-by: Andrei Zubkov
Discussion: https://postgr.es/m/7beb722dd016bf54f1c78bfd6d44a684e28da624.camel@moonset.ru

Author: michaelpq

contrib/pg_stat_statements/expected/level_tracking.out

@@ -202,3 +202,9 @@ SELECT calls, rows, query FROM pg_stat_statements ORDER BY query COLLATE "C";
 -------+------+-------
 (0 rows)
 
+SELECT pg_stat_statements_reset();
+ pg_stat_statements_reset 
+--------------------------
+ 
+(1 row)
+

contrib/pg_stat_statements/expected/user_activity.out

@@ -197,3 +197,9 @@ SELECT query, calls, rows FROM pg_stat_statements ORDER BY query COLLATE "C";
 --
 DROP ROLE regress_stats_user1;
 DROP ROLE regress_stats_user2;
+SELECT pg_stat_statements_reset();
+ pg_stat_statements_reset 
+--------------------------
+ 
+(1 row)
+

contrib/pg_stat_statements/expected/utility.out

@@ -554,3 +554,9 @@ SELECT calls, rows, query FROM pg_stat_statements ORDER BY query COLLATE "C";
      1 |    0 | SET work_mem = '2MB'
 (7 rows)
 
+SELECT pg_stat_statements_reset();
+ pg_stat_statements_reset 
+--------------------------
+ 
+(1 row)
+

contrib/pg_stat_statements/expected/wal.out

@@ -13,17 +13,14 @@ wal_bytes > 0 as wal_bytes_generated,
 wal_records > 0 as wal_records_generated,
 wal_records >= rows as wal_records_ge_rows
 FROM pg_stat_statements ORDER BY query COLLATE "C";
-                                    query                                     | calls | rows | wal_bytes_generated | wal_records_generated | wal_records_ge_rows 
-------------------------------------------------------------------------------+-------+------+---------------------+-----------------------+---------------------
- DELETE FROM pgss_wal_tab WHERE a > $1                                        |     1 |    1 | t                   | t                     | t
- DROP ROLE regress_stats_user1                                                |     1 |    0 | t                   | t                     | t
- DROP ROLE regress_stats_user2                                                |     1 |    0 | t                   | t                     | t
- INSERT INTO pgss_wal_tab VALUES(generate_series($1, $2), $3)                 |     1 |   10 | t                   | t                     | t
- SELECT pg_stat_statements_reset(0,0,0)                                       |     1 |    1 | f                   | f                     | f
- SELECT query, calls, rows FROM pg_stat_statements ORDER BY query COLLATE "C" |     1 |    1 | f                   | f                     | f
- SET pg_stat_statements.track_utility = FALSE                                 |     1 |    0 | f                   | f                     | t
- UPDATE pgss_wal_tab SET b = $1 WHERE a > $2                                  |     1 |    3 | t                   | t                     | t
-(8 rows)
+                            query                             | calls | rows | wal_bytes_generated | wal_records_generated | wal_records_ge_rows 
+--------------------------------------------------------------+-------+------+---------------------+-----------------------+---------------------
+ DELETE FROM pgss_wal_tab WHERE a > $1                        |     1 |    1 | t                   | t                     | t
+ INSERT INTO pgss_wal_tab VALUES(generate_series($1, $2), $3) |     1 |   10 | t                   | t                     | t
+ SELECT pg_stat_statements_reset()                            |     1 |    1 | f                   | f                     | f
+ SET pg_stat_statements.track_utility = FALSE                 |     1 |    0 | f                   | f                     | t
+ UPDATE pgss_wal_tab SET b = $1 WHERE a > $2                  |     1 |    3 | t                   | t                     | t
+(5 rows)
 
 SELECT pg_stat_statements_reset();
  pg_stat_statements_reset 

contrib/pg_stat_statements/sql/level_tracking.sql

@@ -97,3 +97,4 @@ SELECT 1 AS "one";
 SELECT 1 + 1 AS "two";
 
 SELECT calls, rows, query FROM pg_stat_statements ORDER BY query COLLATE "C";
+SELECT pg_stat_statements_reset();

contrib/pg_stat_statements/sql/user_activity.sql

@@ -63,3 +63,4 @@ SELECT query, calls, rows FROM pg_stat_statements ORDER BY query COLLATE "C";
 --
 DROP ROLE regress_stats_user1;
 DROP ROLE regress_stats_user2;
+SELECT pg_stat_statements_reset();

contrib/pg_stat_statements/sql/utility.sql

@@ -276,3 +276,4 @@ SET enable_seqscan = on;
 RESET enable_seqscan;
 
 SELECT calls, rows, query FROM pg_stat_statements ORDER BY query COLLATE "C";
+SELECT pg_stat_statements_reset();