Update SQL statements in docs for Synapse Admins (#12536)

changelog.d/12536.doc

+Update SQL statements and replace use of old table `user_stats_historical` in docs for Synapse Admins.

docs/usage/administration/useful_sql_for_admins.md

 ## Some useful SQL queries for Synapse Admins
 
 ## Size of full matrix db
-`SELECT pg_size_pretty( pg_database_size( 'matrix' ) );`
+```sql
+SELECT pg_size_pretty( pg_database_size( 'matrix' ) );
+```
+
 ### Result example:
 ``` 
 pg_size_pretty 
@@ -9,39 +12,19 @@ pg_size_pretty
  6420 MB
 (1 row)
 ```
-## Show top 20 larger rooms by state events count
-```sql
-SELECT r.name, s.room_id, s.current_state_events
-  FROM room_stats_current s
-  LEFT JOIN room_stats_state r USING (room_id)
-  ORDER BY current_state_events DESC
-  LIMIT 20;
-```
-
-and by state_group_events count:
-```sql
-SELECT rss.name, s.room_id, count(s.room_id) FROM state_groups_state s
-LEFT JOIN room_stats_state rss USING (room_id)
-GROUP BY s.room_id, rss.name        
-ORDER BY count(s.room_id) DESC
-LIMIT 20;
-```
-plus same, but with join removed for performance reasons:
-```sql
-SELECT s.room_id, count(s.room_id) FROM state_groups_state s
-GROUP BY s.room_id        
-ORDER BY count(s.room_id) DESC
-LIMIT 20;
-```
 
 ## Show top 20 larger tables by row count
 ```sql
-SELECT relname, n_live_tup as rows
-  FROM pg_stat_user_tables 
+SELECT relname, n_live_tup AS "rows"
+  FROM pg_stat_user_tables
   ORDER BY n_live_tup DESC
   LIMIT 20;
 ```
-This query is quick, but may be very approximate, for exact number of rows use `SELECT COUNT(*) FROM <table_name>`.
+This query is quick, but may be very approximate, for exact number of rows use:
+```sql
+SELECT COUNT(*) FROM <table_name>;
+```
+
 ### Result example:
 ```
 state_groups_state - 161687170
@@ -66,46 +49,19 @@ device_lists_stream - 326903
 user_directory_search - 316433
 ```
 
-## Show top 20 rooms by new events count in last 1 day:
-```sql
-SELECT e.room_id, r.name, COUNT(e.event_id) cnt FROM events e
-LEFT JOIN room_stats_state r USING (room_id)
-WHERE e.origin_server_ts >= DATE_PART('epoch', NOW() - INTERVAL '1 day') * 1000 GROUP BY e.room_id, r.name ORDER BY cnt DESC LIMIT 20;
-```
-
-## Show top 20 users on homeserver by sent events (messages) at last month:
-```sql
-SELECT user_id, SUM(total_events) 
-   FROM user_stats_historical
-   WHERE TO_TIMESTAMP(end_ts/1000) AT TIME ZONE 'UTC' > date_trunc('day', now() - interval '1 month')
-   GROUP BY user_id
-   ORDER BY SUM(total_events) DESC 
-   LIMIT 20;
-```
-
-## Show last 100 messages from needed user, with room names:
-```sql
-SELECT e.room_id, r.name, e.event_id, e.type, e.content, j.json FROM events e
-  LEFT JOIN event_json j USING (room_id)
-  LEFT JOIN room_stats_state r USING (room_id)
-  WHERE sender = '@LOGIN:example.com'
-  AND e.type = 'm.room.message'
-  ORDER BY stream_ordering DESC
-  LIMIT 100;
-```
-
 ## Show top 20 larger tables by storage size
 ```sql
 SELECT nspname || '.' || relname AS "relation",
-    pg_size_pretty(pg_total_relation_size(C.oid)) AS "total_size"
-  FROM pg_class C
-  LEFT JOIN pg_namespace N ON (N.oid = C.relnamespace)
+    pg_size_pretty(pg_total_relation_size(c.oid)) AS "total_size"
+  FROM pg_class c
+  LEFT JOIN pg_namespace n ON (n.oid = c.relnamespace)
   WHERE nspname NOT IN ('pg_catalog', 'information_schema')
-    AND C.relkind <> 'i'
+    AND c.relkind <> 'i'
     AND nspname !~ '^pg_toast'
-  ORDER BY pg_total_relation_size(C.oid) DESC
+  ORDER BY pg_total_relation_size(c.oid) DESC
   LIMIT 20;
 ```
+
 ### Result example:
 ```
 public.state_groups_state - 27 GB
@@ -130,8 +86,93 @@ public.device_lists_remote_cache - 124 MB
 public.state_group_edges - 122 MB
 ```
 
+## Show top 20 larger rooms by state events count
+You get the same information when you use the
+[admin API](../../admin_api/rooms.md#list-room-api)
+and set parameter `order_by=state_events`.
+
+```sql
+SELECT r.name, s.room_id, s.current_state_events
+  FROM room_stats_current s
+  LEFT JOIN room_stats_state r USING (room_id)
+  ORDER BY current_state_events DESC
+  LIMIT 20;
+```
+
+and by state_group_events count:
+```sql
+SELECT rss.name, s.room_id, COUNT(s.room_id)
+  FROM state_groups_state s
+  LEFT JOIN room_stats_state rss USING (room_id)
+  GROUP BY s.room_id, rss.name
+  ORDER BY COUNT(s.room_id) DESC
+  LIMIT 20;
+```
+
+plus same, but with join removed for performance reasons:
+```sql
+SELECT s.room_id, COUNT(s.room_id)
+  FROM state_groups_state s
+  GROUP BY s.room_id 
+  ORDER BY COUNT(s.room_id) DESC
+  LIMIT 20;
+```
+
+## Show top 20 rooms by new events count in last 1 day:
+```sql
+SELECT e.room_id, r.name, COUNT(e.event_id) cnt
+  FROM events e
+  LEFT JOIN room_stats_state r USING (room_id)
+  WHERE e.origin_server_ts >= DATE_PART('epoch', NOW() - INTERVAL '1 day') * 1000
+  GROUP BY e.room_id, r.name 
+  ORDER BY cnt DESC
+  LIMIT 20;
+```
+
+## Show top 20 users on homeserver by sent events (messages) at last month:
+Caution. This query does not use any indexes, can be slow and create load on the database.
+```sql
+SELECT COUNT(*), sender
+  FROM events
+  WHERE (type = 'm.room.encrypted' OR type = 'm.room.message')
+    AND origin_server_ts >= DATE_PART('epoch', NOW() - INTERVAL '1 month') * 1000
+  GROUP BY sender
+  ORDER BY COUNT(*) DESC
+  LIMIT 20;
+```
+
+## Show last 100 messages from needed user, with room names:
+```sql
+SELECT e.room_id, r.name, e.event_id, e.type, e.content, j.json
+  FROM events e
+  LEFT JOIN event_json j USING (room_id)
+  LEFT JOIN room_stats_state r USING (room_id)
+  WHERE sender = '@LOGIN:example.com'
+    AND e.type = 'm.room.message'
+  ORDER BY stream_ordering DESC
+  LIMIT 100;
+```
+
 ## Show rooms with names, sorted by events in this rooms
-`echo "select event_json.room_id,room_stats_state.name from event_json,room_stats_state where room_stats_state.room_id=event_json.room_id" | psql synapse | sort | uniq -c | sort -n`
+
+**Sort and order with bash**
+```bash
+echo "SELECT event_json.room_id, room_stats_state.name FROM event_json, room_stats_state \
+WHERE room_stats_state.room_id = event_json.room_id" | psql -d synapse -h localhost -U synapse_user -t \
+| sort | uniq -c | sort -n
+```
+Documentation for `psql` command line parameters: https://www.postgresql.org/docs/current/app-psql.html
+
+**Sort and order with SQL**
+```sql
+SELECT COUNT(*), event_json.room_id, room_stats_state.name
+  FROM event_json, room_stats_state
+  WHERE room_stats_state.room_id = event_json.room_id
+  GROUP BY event_json.room_id, room_stats_state.name
+  ORDER BY COUNT(*) DESC
+  LIMIT 50;
+```
+
 ### Result example:
 ```
    9459  !FPUfgzXYWTKgIrwKxW:matrix.org              | This Week in Matrix
@@ -145,12 +186,22 @@ public.state_group_edges - 122 MB
 ```
 
 ## Lookup room state info by list of room_id
+You get the same information when you use the
+[admin API](../../admin_api/rooms.md#room-details-api).
 ```sql
-SELECT rss.room_id, rss.name, rss.canonical_alias, rss.topic, rss.encryption, rsc.joined_members, rsc.local_users_in_room, rss.join_rules
-FROM room_stats_state rss
-LEFT JOIN room_stats_current rsc USING (room_id)
-WHERE room_id IN (WHERE room_id IN (
- '!OGEhHVWSdvArJzumhm:matrix.org',
- '!YTvKGNlinIzlkMTVRl:matrix.org'
-)
-```
\ No newline at end of file
+SELECT rss.room_id, rss.name, rss.canonical_alias, rss.topic, rss.encryption,
+    rsc.joined_members, rsc.local_users_in_room, rss.join_rules
+  FROM room_stats_state rss
+  LEFT JOIN room_stats_current rsc USING (room_id)
+  WHERE room_id IN ( WHERE room_id IN (
+    '!OGEhHVWSdvArJzumhm:matrix.org',
+    '!YTvKGNlinIzlkMTVRl:matrix.org' 
+  );
+```
+
+## Show users and devices that have not been online for a while
+```sql
+SELECT user_id, device_id, user_agent, TO_TIMESTAMP(last_seen / 1000) AS "last_seen"
+  FROM devices
+  WHERE last_seen < DATE_PART('epoch', NOW() - INTERVAL '3 month') * 1000;
+```