session_query_ids

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.

Examples

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;