features: run single-shot multi-query sub-queries concurrently#558
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A multi-feature query can run single-shot - one pass per (sub-query, table), with no meta query, no chunking and no key-range window - using a server-side cursor to keep memory bounded; an optional per-sub-query maximum bounds each sub-query. When paged, numberMatched is computed across all sub-queries (the invariant total) while value queries are executed only for the sub-queries needed for the page.
Single-shot multi-queries read every sub-query in one pass with no cross-sub-query dependency, so the sub-queries can now execute concurrently while their rows are still emitted in sub-query order: - the value phase uses an order-preserving concurrent flat-map over the sub-queries (Transformer.flatMapConcurrent); - each sub-query's value queries are subscribed on a worker thread (SqlQueryOptions.isParallel) so the blocking JDBC reads actually overlap instead of running on a single thread; - a shared connection-budget semaphore (sized to the pool) bounds the connections held by the in-flight sub-queries and acquires each sub-query's permits as a block, so concurrent requests cannot deadlock by each holding part of the pool. Paged and single-feature reads keep the serial path. Requires the matching xtraplatform-core operators flatMapConcurrent and guarded.
azahnen
approved these changes
Jul 10, 2026
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Depends on #555.
Depends on ldproxy/xtraplatform#428.
Single-shot multi-queries read every sub-query in one pass with no cross-sub-query dependency, so the sub-queries can now execute concurrently while their rows are still emitted in sub-query order:
Paged and single-feature reads keep the serial path. Requires the matching xtraplatform-core operators flatMapConcurrent and guarded.