HTTP Response Headers

When a query is executed using the HTTP end-point the response has a number of headers applied that can be used later.

HTTP/2 200 
date: Tue, 29 Jun 2021 09:32:06 GMT
content-type: application/json; charset=UTF-8
x-clickhouse-query-id: c4f6aba2-480f-4f67-9d5d-5662e44b45dc
x-clickhouse-format: JSON
x-clickhouse-timezone: UTC
x-hdx-query-stats: exec_time=4271 rows_read=0 bytes_read=0 num_partitions=4 num_peers=2
traceparent: 00-9e94d8306114a074da5393950ff481ac-cace2fb519dc02bb-01

Header	Description	Example
x-clickhouse-query-id	Unique query identifier, supplied each time a query is executed.	c4f6aba2-480f-4f67-9d5d-5662e44b45dc
x-clickhouse-format	The format of the response Body.	JSON
x-clickhouse-timezone	The time zone applied to the data.	UTC
x-hdx-query-stats	Statistics and information covering how the query was executed and by how many resources	`exec_time=545 rows_read=48516556 bytes_read=194066224 num_partitions=18 num_peers=1`
traceparent	The traceId that can be used to look up the query trace within Tempo	00-9e94d8306114a074da5393950ff481ac-cace2fb519dc02bb-01

x-hdx-query-stats

The Query stats supply the following information.

Query_stat	Description
exec_time	Execution time of the query in milliseconds
rows_read	Number of rows read to supply to answer the query
bytes_read	Number of uncompressed bytes parsed to answer the query
num_partitions	Number of HDX partitions accessed to answer the query
num_peers	Number of query-peers accessed to answer the query