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Pass 2: sliding-window and Exponential Histogram composition — after #511 #522
Description
Goal
The rest of #509's window-composition rule, after tumbling windows (#518):
- Sliding window: one summary per active window, with each sample inserted into every active window. Works for non-mergeable summaries; costs more ingestion work and memory.
- Exponential Histogram: EH buckets that grow with age cover a long history. A query window merges the buckets it covers, with approximate boundaries for old windows. Example 3 Pattern A and Example 4 Pattern A in docs: propose workload-wide planning, summary sharing, and materialization #509.
Blocked on
Implementation of #511 (unified operator graph: OperatorNode with common metadata, no KeepPreAsap wrappers). Do not start before #511 is implemented.
Also depends on #518 (tumbling), and on two #509 TODOs: the design of summary subtract/delete nodes, and query-time materialization in physical planning.
Current state
SummaryWindowFramework { Tumbling, Sliding, ExponentialHistogram }exists (types/src/post_asap/summary_window.rs).- EH accuracy evidence exists in
summary_maintenance_cost/window.rs. - The framework is chosen only from provider evidence registered in tests, so it is always
Nonein production.
To decide
- How EH boundary error enters the accuracy model.
- Which families are eligible, and how they interact with subtract/delete.
- How an EH built once at query time is materialized for a batch of queries (docs: propose workload-wide planning, summary sharing, and materialization #509 Example 4 Pattern A).
Activity
zzylol commentedon Oct 15, 2026
Status: planned with the window-grid work. It comes after the tumbling-pane Pass 2 rule (#518, in progress) and Stage 2 materialization (materialization enumeration and
MatAtQuery).These acceptance tests are
#[ignore]d on main for sliding windows or EH:crates/integration-tests/tests/planner_layering_example3.rsstage1_logical_asap_optimization_a_window_composition_adds_one_eh_for_all_five,…_a_keeps_independent_and_shared_window_summaries,…_a_window_composition_groups_every_pairstage1_logical_asap_optimization_b_window_composition_adds_sliding_and_tumbling_per_option,…_b_merge_only_where_the_window_form_needs_itcrates/integration-tests/tests/planner_layering_example4.rsstage2_physical_asap_optimization_a_shared_eh_has_three_materialization_options,…_a_at_rest_drops_the_ingestion_time_option,…_a_materialized_eh_is_built_once_for_all_consumers,stage3_plan_selection_a_rebuilding_per_query_costs_more_than_building_once,…_a_once_adhoc_prefers_the_query_time_eh,…_a_monthly_amortizes_ingestion_time_maintenancestage2_physical_asap_optimization_b_sliding_kll_has_two_materialization_optionsThe other Example 4 Pattern B tests (tumbling KLL,
b1/b3,stage3_plan_selection_b_*) are ignored only for tumbling windows and materialization. They belong to #518 and the Stage 2 materialization work.