Add stats_reset column to pg_stat_database_conflicts.

This commit adds a stats_reset column to pg_stat_database_conflicts,
allowing users to see when the statistics in this view were last reset.
This makes the view consistent with pg_stat_database and other statistics
views.

Catalog version bumped.

Author: Shihao Zhong <zhong950419@gmail.com>
Reviewed-by: Sami Imseih <samimseih@gmail.com>
Reviewed-by: Kirill Reshke <reshkekirill@gmail.com>
Reviewed-by: Chao Li <li.evan.chao@gmail.com>
Reviewed-by: Fujii Masao <masao.fujii@gmail.com>
Discussion: https://postgr.es/m/CAGRkXqS98OebEWjax99_LVAECsxCB8i=BfsdAL34i-5QHfwyOQ@mail.gmail.com

doc/src/sgml/monitoring.sgml

@@ -4036,6 +4036,15 @@ description | Waiting for a newly initialized WAL file to reach durable storage
        on the primary
       </para></entry>
      </row>
+
+     <row>
+      <entry role="catalog_table_entry"><para role="column_definition">
+       <structfield>stats_reset</structfield> <type>timestamp with time zone</type>
+      </para>
+      <para>
+       Time at which these statistics were last reset
+      </para></entry>
+     </row>
     </tbody>
    </tgroup>
   </table>

src/backend/catalog/system_views.sql

@@ -1163,7 +1163,8 @@ CREATE VIEW pg_stat_database_conflicts AS
             pg_stat_get_db_conflict_snapshot(D.oid) AS confl_snapshot,
             pg_stat_get_db_conflict_bufferpin(D.oid) AS confl_bufferpin,
             pg_stat_get_db_conflict_startup_deadlock(D.oid) AS confl_deadlock,
-            pg_stat_get_db_conflict_logicalslot(D.oid) AS confl_active_logicalslot
+            pg_stat_get_db_conflict_logicalslot(D.oid) AS confl_active_logicalslot,
+            pg_stat_get_db_stat_reset_time(D.oid) AS stats_reset
     FROM pg_database D;
 
 CREATE VIEW pg_stat_user_functions AS

src/include/catalog/catversion.h

@@ -57,6 +57,6 @@
  */
 
 /*							yyyymmddN */
-#define CATALOG_VERSION_NO	202603101
+#define CATALOG_VERSION_NO	202603131
 
 #endif

src/test/regress/expected/rules.out

@@ -1921,7 +1921,8 @@ pg_stat_database_conflicts| SELECT oid AS datid,
     pg_stat_get_db_conflict_snapshot(oid) AS confl_snapshot,
     pg_stat_get_db_conflict_bufferpin(oid) AS confl_bufferpin,
     pg_stat_get_db_conflict_startup_deadlock(oid) AS confl_deadlock,
-    pg_stat_get_db_conflict_logicalslot(oid) AS confl_active_logicalslot
+    pg_stat_get_db_conflict_logicalslot(oid) AS confl_active_logicalslot,
+    pg_stat_get_db_stat_reset_time(oid) AS stats_reset
    FROM pg_database d;
 pg_stat_gssapi| SELECT pid,
     gss_auth AS gss_authenticated,

src/test/regress/expected/stats.out

@@ -1131,8 +1131,10 @@ SELECT stats_reset > :'wal_reset_ts'::timestamptz FROM pg_stat_wal;
 SELECT pg_stat_reset_shared('unknown');
 ERROR:  unrecognized reset target: "unknown"
 HINT:  Target must be "archiver", "bgwriter", "checkpointer", "io", "recovery_prefetch", "slru", or "wal".
--- Test that reset works for pg_stat_database
--- Since pg_stat_database stats_reset starts out as NULL, reset it once first so we have something to compare it to
+-- Test that reset works for pg_stat_database and pg_stat_database_conflicts
+-- Since pg_stat_database stats_reset starts out as NULL, reset it once first so that we
+-- have a baseline for comparison. The same for pg_stat_database_conflicts as it shares
+-- the same stats_reset as pg_stat_database.
 SELECT pg_stat_reset();
  pg_stat_reset 
 ---------------
@@ -1140,6 +1142,13 @@ SELECT pg_stat_reset();
 (1 row)
 
 SELECT stats_reset AS db_reset_ts FROM pg_stat_database WHERE datname = (SELECT current_database()) \gset
+SELECT stats_reset AS dbc_reset_ts FROM pg_stat_database_conflicts WHERE datname = (SELECT current_database()) \gset
+SELECT :'db_reset_ts'::timestamptz = :'dbc_reset_ts'::timestamptz;
+ ?column? 
+----------
+ t
+(1 row)
+
 SELECT pg_stat_reset();
  pg_stat_reset 
 ---------------
@@ -1152,6 +1161,12 @@ SELECT stats_reset > :'db_reset_ts'::timestamptz FROM pg_stat_database WHERE dat
  t
 (1 row)
 
+SELECT stats_reset > :'dbc_reset_ts'::timestamptz FROM pg_stat_database_conflicts WHERE datname = (SELECT current_database());
+ ?column? 
+----------
+ t
+(1 row)
+
 ----
 -- pg_stat_get_snapshot_timestamp behavior
 ----

src/test/regress/sql/stats.sql

@@ -523,13 +523,18 @@ SELECT stats_reset > :'wal_reset_ts'::timestamptz FROM pg_stat_wal;
 -- Test error case for reset_shared with unknown stats type
 SELECT pg_stat_reset_shared('unknown');
 
--- Test that reset works for pg_stat_database
+-- Test that reset works for pg_stat_database and pg_stat_database_conflicts
 
--- Since pg_stat_database stats_reset starts out as NULL, reset it once first so we have something to compare it to
+-- Since pg_stat_database stats_reset starts out as NULL, reset it once first so that we
+-- have a baseline for comparison. The same for pg_stat_database_conflicts as it shares
+-- the same stats_reset as pg_stat_database.
 SELECT pg_stat_reset();
 SELECT stats_reset AS db_reset_ts FROM pg_stat_database WHERE datname = (SELECT current_database()) \gset
+SELECT stats_reset AS dbc_reset_ts FROM pg_stat_database_conflicts WHERE datname = (SELECT current_database()) \gset
+SELECT :'db_reset_ts'::timestamptz = :'dbc_reset_ts'::timestamptz;
 SELECT pg_stat_reset();
 SELECT stats_reset > :'db_reset_ts'::timestamptz FROM pg_stat_database WHERE datname = (SELECT current_database());
+SELECT stats_reset > :'dbc_reset_ts'::timestamptz FROM pg_stat_database_conflicts WHERE datname = (SELECT current_database());
 
 
 ----