perf: round 5 — CalDAV cursor streaming, SPA interning gaps, NC href prefix, per-request micro-allocs
Seven benchmark-gated changes (benches/ROUND5.md; BEFORE/AFTER bench + equivalence gate each, rollback rule as ROUND2-4 — two intermediate CalDAV shapes measured worse and were themselves rolled back before shipping): - CalDAV whole-calendar responses (REPORT no-range/sync-collection, depth-1 collection PROPFIND, .ics GET): buffered double-residency → ONE window-ordered scan (MIN(start_time) OVER (PARTITION BY ical_uid)) streamed through a PG cursor, pages cut at UID boundaries. TTFB 23.3→11.0 ms (2.1x), peak heap 14.2→8.0 MiB at 4k events / 45→24 MiB at 12k, wall +9-15% (documented trade, ZIP-streaming class); both multistatus and ICS byte-identical to the buffered output. Rejected shapes kept in the doc: per-page GROUP-BY keyset (3-4x wall) and per-uid ANY hydration (~20 µs/index descent). - SPA listing interning gaps: folder/recent/favorites resources handlers (and the WebDAV pseudo-root) called raw Arc::from per row for the closed display set ROUND3 interned — now intern_display/intern_mime, 4→0 allocs/row, byte-identical Arc contents. - NC PROPFIND child hrefs: username + parent path encoded once per request instead of per child (543→165 ns/row, 13→4 allocs); native WebDAV href drops its intermediate encode String. - suggest enrichment: entity clone + field re-clones per keystroke row → consume + move (166.5→126.8 µs/200 rows, 20→7 allocs/row). - list_readable_by returns the cache's Arc (246→128 ns warm hit, 4→0 allocs) — deep Vec clone per DAV-selector request removed. - CardDAV REPORT: borrowed props, reused href buffer, exact-size etag quoting (3.04→2.34 ms per 5k-contact getetag poll). - Auth span records: user_id.to_string() per request ×3 → tracing::field::display. Checks: cargo fmt, clippy --all-features --all-targets -D warnings, cargo test --workspace (523 passed). Follow-ups (CardDAV streaming, &[&str] id batches, ::text UUID casts A/B, share-landing join) recorded in benches/ROUND5.md. Co-Authored-By: Claude Fable 5 <noreply@anthropic.com> Claude-Session: https://claude.ai/code/session_017aJu9ghvuT8WqC31ZEGTBA
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# Round 5 — CalDAV streaming, SPA interning gaps, NC href prefix, per-request micro-allocs
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Benchmark-gated changes, same rule as ROUND2-4: every change ships with a
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BEFORE/AFTER benchmark; an AFTER that doesn't beat its BEFORE gets rolled
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back. Equivalence gates (byte-identical responses / identical outputs)
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guard every behavior-preserving rewrite.
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Measured on 4 cores / 15 GiB, local PostgreSQL 16 (fsync off), release
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profile. Reproduce any row with the command in its section.
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## Summary
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| # | change | key metric | before → after |
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|--:|---|---|---|
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| 1 | CalDAV whole-calendar streaming | TTFB / peak heap (4k events) | 23.3 → 11.0 ms (**2.1x**) / 14.2 → 8.0 MiB (**1.8x**) |
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| 2 | SPA listing interning gaps closed | allocs/row closed-set fields | 4 → 0 (wall parity) |
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| 3 | NC PROPFIND child-href prefix | ns/row href build | 543 → 165 (**3.3x**), 13 → 4 allocs |
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| 4 | suggest enrichment consume | µs/keystroke (200 rows) | 166.5 → 126.8 (**1.31x**), 20 → 7 allocs/row |
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| 5 | `list_readable_by` Arc hit | ns/hit warm | 246 → 128 (**1.9x**), 4 → 0 allocs |
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| 6 | CardDAV REPORT churn | µs/5k-contact getetag poll | 3044 → 2340 (**1.30x**) |
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| 7 | auth span records | allocs/request | 3 → 0 (field::display) |
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## [1] CalDAV whole-calendar responses — buffered double-residency → cursor streaming
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The REPORT path (no-range `calendar-query`, `sync-collection`), the
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depth-1 collection PROPFIND (both URL shapes) and the whole-calendar
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`.ics` GET all (a) materialised EVERY event DTO of the calendar in one
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Vec — each row carrying its full `ical_data` body — then (b) rendered
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the complete multistatus / VCALENDAR into a second in-RAM buffer: the
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calendar resident twice per request, TTFB = full generation time.
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Now `CalendarEventRepository::stream_events_uid_order` serves ONE
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window-ordered scan (`ORDER BY MIN(start_time) OVER (PARTITION BY
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ical_uid), ical_uid, master-first, start_time`) through a PG cursor —
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same-UID rows (recurring master + exception overrides) arrive adjacent,
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bundle order equals the buffered listing's first-appearance order — and
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the handlers cut emit pages at UID boundaries, streaming header →
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page chunks → footer through the split adapter writers
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(`write_caldav_multistatus_start` / `write_report_page` /
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`write_collection_head` / `write_collection_event_page`). Bounded
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shapes (time-range query, multiget, single-event GET) keep the buffered
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path. The Read authz gate runs once before the cursor opens.
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The shape was itself benchmark-driven: a first keyset pager over the
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`GROUP BY` re-aggregated the calendar per page (3-4x total wall —
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rolled back), and per-uid `= ANY(page)` hydration paid ~20 µs per index
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descent (~4x the sequential scan — rolled back). The shipped design
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streams ONE window-ordered scan
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(`ORDER BY MIN(start_time) OVER (PARTITION BY ical_uid), …`) through a
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PG cursor, cutting emit pages at UID boundaries.
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```
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cargo run --release --features bench --example bench_caldav_stream
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# 4000 events (20% exceptions) TTFB ms wall ms peak heap MiB
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# BEFORE (buffered) 23.3 23.3 14.2
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# AFTER (streamed) 11.0 25.4 8.0 TTFB 2.1x, heap 1.8x
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# 12000 events
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# BEFORE 79.5 79.5 45.0
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# AFTER 43.9 91.5 24.2 TTFB 1.8x, heap 1.9x
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# Trade: wall +9-15% (the window sort + cursor) for ~2x lower peak RAM
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# — which scales with calendar size and per concurrent sync client —
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# and ~2x faster first byte. Same trade class as ROUND2's ZIP
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# streaming. Gates: multistatus AND .ics byte-identical to buffered.
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```
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## [2] SPA listing rows — interning bypass closed
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ROUND3 added `intern_display` / `intern_mime` so `File→FileDto` stops
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allocating for the ~60-string closed set (icon class, category, mime).
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But the three hottest web-UI listing endpoints — the folder navigation
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(`/folders/{id}/resources`), `/recent/resources` and
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`/favorites/resources` — plus the WebDAV drive pseudo-root build their
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DTOs by hand and called raw `Arc::from` per row, re-introducing 3-4
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alloc+copies per row the intern tables exist to remove. All four sites
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now route through the intern lookups; returned `Arc<str>` contents are
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byte-identical.
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## [3] NC PROPFIND child hrefs — per-row prefix re-encode → precomputed
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`nc_href` re-encoded the username and re-split + re-encoded the whole
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parent path for EVERY child row of every NextCloud PROPFIND page (up to
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500/page), preceded by a per-row `format!` of the joined subpath — only
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the name segment actually varies. The prefix is now encoded once per
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request; each row appends its encoded name (native WebDAV href also
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dropped its intermediate encode String — the percent-encode `Display`
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adapter feeds `format!` directly).
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## [4-6] Per-request micro-allocs (suggest, readable-cache, CardDAV)
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- **suggest** deep-cloned every entity into the DTO conversion and then
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cloned name/id/path AGAIN per row — on an every-keystroke path. Now
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consumes + moves.
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- **`list_readable_by`** returned a fresh deep clone of the cached
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drive Vec (every row's Strings) per warm hit — per DAV request with an
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explicit selector. It now returns the cache's `Arc` (refcount bump);
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the only caller that needs owned rows (`GET /api/drives`) clones just
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its response rows.
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- **CardDAV REPORT** cloned the requested-props Vec per REPORT,
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allocated a fresh href String per contact and `format!`ed each quoted
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etag — the same shapes ROUND4 removed from CalDAV. Now: borrowed
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props, one reused href buffer, exact-size quoting.
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```
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cargo run --release --features bench --example bench_micro_allocs
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# [1] suggest (200 rows) 166.5 → 126.8 µs 1.31x 20.0 → 7.0 allocs/row
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# [2] readable warm hit 246.4 → 127.7 ns 1.9x 4 → 0 allocs/hit
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# [3] closed-set fields 129.9 → 136.3 ns 1.0x 4 → 0 allocs/row
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# (wall parity under the bench's System allocator; the win is the
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# removed allocator traffic + consistency with the interned
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# FileDto::from path — ROUND3 #9)
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# [4] NC child hrefs 543.1 → 164.5 ns 3.3x 13 → 4 allocs/row
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# [5] CardDAV getetag (5k) 3043.8 → 2339.5 µs 1.30x
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# gates: identical outputs / byte-identical XML on every section
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```
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## [7] Auth middleware span records
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`tracing::Span::current().record("user_id", user_id.to_string())`
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allocated a 36-byte String per authenticated request (×3 auth paths).
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`tracing::field::display(user_id)` records lazily — the subscriber
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formats into its own buffer.
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## Follow-ups worth a future round (confirmed real, not gated here)
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- CardDAV multistatus is still fully buffered — port the CalDAV
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streaming emitter once contacts get a keyset pager (current
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`get_contacts_by_address_book_paginated` is LIMIT/OFFSET, the
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quadratic shape PROPFIND-PAGING replaced elsewhere).
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- CalDAV time-range REPORT still buffers (bounded by the range, but a
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year-wide range on a dense calendar is large).
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- `batch_resolve_ids` / `batch_check_favorites` take `&[String]` — every
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NC PROPFIND page clones ~500 id Strings that the services re-parse to
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`Uuid` anyway; switch the chain to `&[&str]` (8 call sites).
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- Hot listing SQL casts UUID columns to `::text` server-side (~18 sites
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in `file_blob_read_repository.rs`) — decode as `Uuid` + format
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app-side; needs a local-PG A/B before adopting.
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- Public-share landing runs register + fetch serially — `tokio::join!`
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or fold the increment into the fetch with `RETURNING`.
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- `CurrentUser` still clones username/email per request; zero-alloc
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needs the JWT cache to hold `Arc<str>` claims.
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- Grouped/swimlane files view virtualization (frontend, carried since
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ROUND3).
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