system.session_query_ids

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Description

• The currently running query is already visible when it selects from the table.
• Failed queries are recorded too — retrieving the id of a query that just failed is a primary use case.

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Columns

• sequence_number (UInt64) — Position of the query within the session, monotonically increasing.
• query_id (String) — The query id, can be joined with system.query_log.

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Session scoping per interface

• Native/TCP connections (clickhouse-client, drivers) and clickhouse-local: the session is the connection, so the history accumulates across all queries of the connection, including multi-query client invocations.
• HTTP with the session_id parameter: the history persists across requests that pass the same session_id, until the session expires.
• HTTP without session_id: every request is its own session, so the table only ever shows the current query.

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History size

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TRUNCATE

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Example

SELECT 1 FORMAT Null;
SELECT 2 FORMAT Null;

SELECT * FROM system.session_query_ids;

┌─sequence_number─┬─query_id─────────────────────────────┐
│               1 │ 4c9e97a3-b806-4a5c-9a94-5a614c3d0b3f │
│               2 │ 8f9a2f59-30d3-4f8e-b3a1-6a0c1a4d3e2b │
│               3 │ f2b1c4d8-7e6a-4b5c-8d9e-0a1b2c3d4e5f │
└─────────────────┴──────────────────────────────────────┘

SYSTEM FLUSH LOGS query_log;

SELECT query_id, type, query, query_duration_ms
FROM system.query_log
WHERE query_id IN (SELECT query_id FROM system.session_query_ids)
ORDER BY event_time_microseconds;

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See also

• system.query_log — details of executed queries
• session_query_ids_history_size setting