docs: missing documentation for system.processes system table

[sundy-li]

What's Missing

The system.processes system table is implemented in the Databend source code but has no documentation page in the docs.

Source File

/workspace/databend/src/query/storages/system/src/processes_table.rs

The table is registered as system.processes (see const NAME: &'static str = "system.processes").

What It Does

system.processes exposes information about currently running queries and connections on the Databend cluster. It includes the following columns:

Column	Type	Description
node	String	The cluster node where the process is running
id	String	Process/query ID
type	String	Process type
host	String	Client host address
user	String	User running the query
command	String	SQL command being executed
database	String	Current database
extra_info	String	Additional process information
memory_usage	Int64	Memory used by the process (bytes)
data_read_bytes	Int64	Bytes read
data_write_bytes	Int64	Bytes written
scan_progress_read_rows	Int64	Rows scanned so far
scan_progress_read_bytes	Int64	Bytes scanned so far
mysql_connection_id	UInt32	MySQL protocol connection ID
time	UInt64	Elapsed time (seconds)
created_time	Timestamp	When the process started
status	String	Current process status
current_query_id	String	Current query ID

This table is distributed at the warehouse level (DISTRIBUTION_LEVEL = DistributionLevel::Warehouse), meaning it aggregates process information across all nodes in the warehouse.

Suggested Doc Location

/docs/en/sql-reference/00-sql-reference/31-system-tables/system-processes.md

This should follow the same format as other system table docs such as system-query-log.md and system-settings.md.