Client packets

value	name	description
0	Hello	Client handshake start
1	Query	Query request
2	Data	Block with data
3	Cancel	Cancel query
4	Ping	Ping request
5	TableStatus	Table status request

The Data can be compressed.

Hello

For example, we are Go Client v1.10 that supports 54451 protocol version and want to connect to default database with default user and secret password.

field	type	value	description
client_name	String	"Go Client"	Client implementation name
version_major	UVarInt	1	Client major version
version_minor	UVarInt	10	Client minor version
protocol_version	UVarInt	54451	TCP Protocol version
database	String	"default"	Database name
username	String	"default"	Username
password	String	"secret"	Password

Protocol version

Protocol version is TCP protocol version of client.

Usually it is equal to the latest compatible server revision, but should not be confused with it.

Defaults

All values should be explicitly set, there are no defaults on server side. On client side, use "default" database, "default" username and "" (blank string) password as defaults.

Query

field	type	value	description
query_id	String	1ff-a123	Query ID, can be UUIDv4
client_info	ClientInfo	See type	Data about client
settings	Settings	See type	List of settings
secret	String	secret	Inter-server secret
stage	UVarInt	2	Execute until query stage
compression	UVarInt	0	Disabled=0, enabled=1
body	String	SELECT 1	Query text

Client info

field	type	description
query_kind	byte	None=0, Initial=1, Secondary=2
initial_user	String	Initial user
initial_query_id	String	Initial query id
initial_address	String	Initial address
initial_time	Int64	Initial time
interface	byte	TCP=1, HTTP=2
os_user	String	OS User
client_hostname	String	Client Hostname
client_name	String	Client Name
version_major	UVarInt	Client major version
version_minor	UVarInt	Client minor version
protocol_version	UVarInt	Client protocol version
quota_key	String	Quota key
distributed_depth	UVarInt	Distributed depth
version_patch	UVarInt	Client patch version
otel	Bool	Trace fields are present
trace_id	FixedString(16)	Trace ID
span_id	FixedString(8)	Span ID
trace_state	String	Tracing state
trace_flags	Byte	Tracing flags

Settings

field	type	value	description
key	String	send_logs_level	Key of setting
value	String	trace	Value of setting
important	Bool	true	Can be ignored or not

Encoded as list, blank key and value denotes end of list.

Stage

value	name	description
0	FetchColumns	Only fetch column types
1	WithMergeableState	Until mergeable state
2	Complete	Until full completeness (should be default)

Data

field	type	description
info	BlockInfo	Encoded block info
columns	UVarInt	Columns count
rows	UVarInt	Rows count
columns	[]Column	Columns with data

Column

field	type	value	description
name	String	foo	Column name
type	String	DateTime64(9)	Column type
data	bytes	~	Column data

Cancel

No packet body. Server should cancel query.

Ping

No packet body. Server should respond with pong.