Add docs for system.user_processes

docs/en/operations/system-tables/user_processes.md

@@ -0,0 +1,28 @@
+---
+slug: /en/operations/system-tables/user_processes
+---
+# user_processes
+
+This system table is used for implementing the `SHOW USER PROCESSES` query.
+
+Columns:
+
+- `user` ([String](../../sql-reference/data-types/string.md)) — User name.
+- `memory_usage` ([Int64](../../sql-reference/data-types/int-uint#int-ranges)) – Sum of RAM used by all processes of the user. It might not include some types of dedicated memory. See the [max_memory_usage](../../operations/settings/query-complexity.md#settings_max_memory_usage) setting.
+- `peak_memory_usage` ([Int64](../../sql-reference/data-types/int-uint#int-ranges)) — The peak of memory usage of the user. It can be reset when no queries are run for the user.
+- `ProfileEvents` ([Map(String, UInt64)](../../sql-reference/data-types/map)) – Summary of ProfileEvents that measure different metrics for the user. The description of them could be found in the table [system.events](../../operations/system-tables/events.md#system_tables-events)
+
+```sql
+SELECT * FROM system.user_processes LIMIT 10 FORMAT Vertical;
+```
+
+```response
+Row 1:
+──────
+user:              default
+memory_usage:      9832
+peak_memory_usage: 9832
+ProfileEvents:     {'Query':5,'SelectQuery':5,'QueriesWithSubqueries':38,'SelectQueriesWithSubqueries':38,'QueryTimeMicroseconds':842048,'SelectQueryTimeMicroseconds':842048,'ReadBufferFromFileDescriptorRead':6,'ReadBufferFromFileDescriptorReadBytes':234,'IOBufferAllocs':3,'IOBufferAllocBytes':98493,'ArenaAllocChunks':283,'ArenaAllocBytes':1482752,'FunctionExecute':670,'TableFunctionExecute':16,'DiskReadElapsedMicroseconds':19,'NetworkSendElapsedMicroseconds':684,'NetworkSendBytes':139498,'SelectedRows':6076,'SelectedBytes':685802,'ContextLock':1140,'RWLockAcquiredReadLocks':193,'RWLockReadersWaitMilliseconds':4,'RealTimeMicroseconds':1585163,'UserTimeMicroseconds':889767,'SystemTimeMicroseconds':13630,'SoftPageFaults':1947,'OSCPUWaitMicroseconds':6,'OSCPUVirtualTimeMicroseconds':903251,'OSReadChars':28631,'OSWriteChars':28888,'QueryProfilerRuns':3,'LogTrace':79,'LogDebug':24}
+
+1 row in set. Elapsed: 0.010 sec.
+```