Set up docs MCP| 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’re 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 shouldn’t 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.