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sql: two-layer nested aggregation (subquery in FROM) is rejected #819
Description
Problem
A two-layer SQL query (an aggregation over a subquery that aggregates the table) is rejected. The pattern parser accepts it, but SQLPatternMatcher::query_info_to_pattern returns QueryError::NestedQueryUnsupported for any query with more than one layer, and the planner rejects it with nested SQL queries are not supported (n=2).
SELECT job, SUM(v) FROM (
SELECT job, instance, SUM(value) AS v FROM data
WHERE time BETWEEN DATEADD(s, -1, NOW()) AND NOW()
GROUP BY job, instance
) GROUP BY jobEquivalent PromQL: sum by (job) (sum by (job, instance) (data))
The PromQL path executes these through the native aggregation DAG; the SQL path has no equivalent.
More examples:
| SQL outer layer over the subquery above | PromQL |
|---|---|
SELECT job, QUANTILE(0.9, v) FROM (...) GROUP BY job |
quantile by (job) (0.9, sum by (job, instance) (data)) |
SELECT job, AVG(v) FROM (...) GROUP BY job |
avg by (job) (sum by (job, instance) (data)) |
SELECT L1, AVG(result) FROM (SELECT L1, L2, QUANTILE(0.95, value) AS result ... GROUP BY L1, L2) GROUP BY L1 |
avg by (L1) (quantile_over_time(0.95, cpu_usage[10s])) |
Reproduce
cargo test -p query_engine_rust --test sql_compliance -- --nocapture; see one-stage-* in nested-aggregations.yaml.
Activity
feat(sql-parser): match two-layer nested aggregation queries
feat(planner): plan two-layer SQL queries as inner query plus query-t…
feat(query-engine): serve two-layer SQL queries via query-time aggreg…
feat(sql-parser): support two-layer nested aggregation queries (#892)