system.session_query_ids

System table containing the query ids of the queries executed in the current session.

Description

Contains the query ids of the queries executed in the current session, in execution order. Use it to find “the queries I just ran” in system.query_log without assigning query_id client-side or tagging queries with log_comment.

The contents are session-scoped: each session sees only its own history, and other sessions’ queries never appear.

A query id is recorded when the query starts, so:

• 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.

Internal queries (system log flushes and similar) are not recorded. Sub-queries that distributed queries run on remote shards are not recorded either - only the initiating query appears, in the initiator’s session.

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.

History size

The history is a ring buffer bounded by the session setting session_query_ids_history_size (default 1000); when the history exceeds this size, the oldest entries are evicted first. Setting it to 0 disables recording; entries recorded earlier stay in the table until truncated or evicted.

The setting is read at query start, before the query is parsed, so a SETTINGS clause of the query itself does not affect whether that query is recorded; use SET, an HTTP URL parameter, or a settings profile instead.

TRUNCATE

TRUNCATE TABLE system.session_query_ids clears the history of the current session. The sequence counter is not reset, so sequence_number values are never reused within a session.

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.

Example

Run a few queries, then fetch their details from system.query_log:

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 │
└─────────────────┴──────────────────────────────────────┘

The current query is recorded at its start, so it appears as the last entry. Timestamps, status, and all other details are available by joining system.query_log:

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;

See also

• system.query_log - Details of executed queries.
• session_query_ids_history_size setting.