perf(agent-sessions): rank the list page first, then net its sessions alone - #1199
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… alone The list read netted every trace of the caller's window to show one page, so its cost and memory grew with the window: seconds per load for an org with long agent runs, and past the list profile's memory on a later page. Where the index can rank the page (every sort and filter but those on cost, tokens and model calls), the list is now two reads: aiSessionRankQuery picks the page's sessions over the window with none of the usage SQL, and aiSessionPageQuery reads those sessions over the page's own extent, filtered per trace before anything is netted. A usage sort or filter still nets every session in one read. The netting compares span ids as 63-bit hashes instead of strings, which is most of what its lookups sort: the reads that still net everything (distributions, usage sorts) take about a quarter less time and a third less memory.
Maple review🟡 Confidence 3/5 · needs attention The Agent Sessions list is split into a rank read over the window and a page read over the ranked page's own extent, and the usage netting now compares span ids as 63-bit hashes. The split and the rekey are faithful; one window-boundary case in the new bounds needs a fix.
Findings🟠 Warning · F1 · Ranked page read counts spans that start after the caller's
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| Change | Kind | Observable | Evidence |
|---|---|---|---|
| aiSessionRankQuery warehouse read (list page, first of two) | outbound | yes | ai-session-reads.ts:219 compiledQuery with { profile: "list", context: "aiSessionsRank" } |
| aiSessionPageQuery ranked read (list page, second of two) | outbound | yes | ai-session-reads.ts:207 compiledQuery with context "aiSessionsPage" |
669a7e9 · Updated on every push. Reply "won't fix" to dismiss a finding, or mention @maple-review-bot to ask about one.
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📝 WalkthroughWalkthroughAI-session listing now uses a rank-then-page query path when the index can rank the requested page. Usage-link IDs and SQL fixtures also change from prefixed strings to numeric hash keys. ChangesAI session reads
Estimated code review effort: 3 (Moderate) | ~25 minutes Change: Bug fix Sequence Diagram(s)sequenceDiagram
participant API
participant listAiSessions
participant aiSessionRankQuery
participant aiSessionPageQuery
participant ClickHouseIndex
API->>listAiSessions: Request session list
listAiSessions->>aiSessionRankQuery: Build ranked page query
aiSessionRankQuery->>ClickHouseIndex: Read session IDs and agent bounds
ClickHouseIndex-->>listAiSessions: Return ranked sessions and bounds
listAiSessions->>aiSessionPageQuery: Build bounded page query
aiSessionPageQuery->>ClickHouseIndex: Read session details
ClickHouseIndex-->>API: Return session rows
Suggested reviewers: 🚥 Pre-merge checks | ✅ 4 | ❌ 1❌ Failed checks (1 warning)
✅ Passed checks (4 passed)
Full details: Docstring CoverageExplanation Docstring coverage is 66.67% which is insufficient. The required threshold is 80.00%. Docstring coverage is scoped to functions touched by this diff. Analyzed 3 functions across 9 files. (1 skipped: 1 unsupported.)
✨ Finishing Touches📝 Generate docstrings
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Inline comments:
Review comments at
@packages/backend/src/services/ai-sessions/ai-session-reads.ts:
- Around line 233-234: Clamp the ranked page-read bound in the
aiSessionPageQuery flow: compute the maximum ranked agentEnd and use the earlier
of it and payload.endTime for fanOutEnd. Leave each row’s agentEnd unchanged,
and add an end-to-end case where a span starts after payload.endTime but before
the unclamped fanOutEnd.
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📒 Files selected for processing (10)
apps/api/src/routes/internal/ai-sessions.http.test.tspackages/backend/src/services/ai-sessions/ai-session-reads.tspackages/backend/src/services/warehouse/ai-trace-index-materialization.clickhouse.e2e.test.tspackages/query-engine-integrations/src/__sql_baseline__/integrations.sqlpackages/query-engine-integrations/src/ai/ai-sessions.test.tspackages/query-engine-integrations/src/ai/ai-sessions.tspackages/query-engine-integrations/src/ai/ai-span-columns.test.tspackages/query-engine-integrations/src/ai/ai-span-columns.tspackages/query-engine-integrations/src/ai/index.tspackages/query-engine-integrations/src/benchmark/index.ts
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The page's upper bound was where its last span ended, applied to where spans start, so a span that started after the caller's endTime and before that point was counted in the row though the ranking never saw it. The ranked read now also keeps to Timestamp <= endTime; the e2e compares both reads over a window that ends inside a turn.
Maple review🟢 Confidence 4/5 · likely safe to merge The delta since the last review clamps the ranked page read to the caller's
Fixed since the last review
What was checked
Observability coverage: 2 of 2 changes observable
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1 participant
Problem
After #1197 the Agent Sessions list loads for orgs with long agent runs, but:
OFFSET 50) hitsMEMORY_LIMIT_EXCEEDEDat thelistprofile's 1.5 GB.Cause:
aiSessionsPagenets usage (ancestor climb + claims) for every trace of the caller's window before it cuts the page to 50 sessions. Cost and memory grow with the window, not with the page.Change
Rank, then read (default sort and every sort/filter except cost, tokens, model calls):
aiSessionRankQuery— which sessions are on the page, over the caller's window. Only the ranking columns; none of the usage SQL is in the text.aiSessionPageQuery({ sessionIds })— the rows of those sessions, over the page's own extent (fanOutStart/fanOutEnd, the same convention/detailsuses). Other sessions inside the bounds are dropped in the per-traceHAVING, before anything is netted.A sort or filter on usage still needs every session netted, so it stays one read.
Integer span keys: the netting compares span ids as 63-bit
cityHash64values instead of strings. Its lookups are sorts, so this is most of their cost.Measurements
Local ClickHouse, synthetic org: 1.46M index rows, 75k traces, 420 sessions over 7 days, 4 threads.
Production (our own org, 7 days, interactive profile): the rank query runs in 70 ms.
Verification
ai-trace-index-materialization+ai-toolsClickHouse e2e: 23/23. Catalog analyzer sweep + list handler tests: 457/457.query-engine-integrations: 446/446 (SQL baseline regenerated, two fixtures added). MCP agent-sessions tests: 16/16.Notes
aiSessionsRankandaiSessionsPage.Need help on this PR? Tag
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