mirror of
https://github.com/block/buzz.git
synced 2026-11-06 17:31:19 +00:00
aa749a862e
## Summary
A plain thread-reply read, `{kinds:[9], #h:[channel], #e:[root],
limit:100}`, goes through the generic `query_events` path. That path
gathers every event tagging the root into a `MATERIALIZED` CTE, then
sorts it to keep one page. On a root with 500k replies, each page costs
about 514k buffer reads plus a temp-file spill.
This PR serves single-root reply reads from `thread_metadata` instead.
It walks `idx_thread_metadata_window` newest-first, fetches each reply
by primary key, and applies every filter predicate before `LIMIT`. Page
cost scales with the page size, not with the thread.
## What changed
- **Routing (`crates/buzz-db/src/store/event.rs`).** A `query_events`
read takes the new route when it has:
- one channel,
- one lowercase-hex `#e` root,
- kinds limited to 9 and/or 40002,
- no `#p` filter (any number of values; the relay marks such filters
`exact_match`),
- no `authors`, `pubkey` or `ids` selector. The route tests those per
reply, so an author with no reply in a hot thread would walk the whole
thread; the generic read narrows by author first.
Every other `#e` read stays on the fenced path from #7854.
- **Root check before routing.** `#e` must name a thread root. A cheap
probe looks up the target in `thread_metadata` first. If the target is
itself a reply, the read takes the generic path, which returns its
direct children the NIP-01 way. A reply counts if its row has a root, or
if it is a rootless legacy stub whose own NIP-10 markers resolve to a
reply.
- **COUNT unchanged.** COUNT post-filter fallbacks (`count.rs`,
`bridge.rs`) set the new `EventQuery::exact_match` flag through
`prepare_count_fallback`. Routing is skipped for them, so COUNT still
counts every event that matches under NIP-01.
- **Same predicates on both paths.** The predicate block moved out of
`build_query_events_sql` into `push_event_filters`, which both paths
call. Filters on the route therefore match the generic path, including
the `#e` tag match, `since`/`until`/`before_id` and deletion.
- **Unnamed statements.** Routed reads run as unnamed statements, so
Postgres plans each one with its root and never caches a generic plan.
The benchmark below shows the routed SQL is also fast under a forced
generic plan, so this is a second safeguard.
- **Narrowed semantics, documented.** Messages that name the root only
in a bare `e` tag, a `mention` tag or a lone `root` marker are top-level
under NIP-10. They have no `thread_metadata` row, so the routed read
omits them. Live subscriptions still deliver them. `docs/nips/NIP-CW.md`
gains a "Plain Thread-reply Filters" section describing this. A client
that needs those messages can add another kind to the filter, which
sends the read down the generic path.
## Benchmark (synthetic, Postgres 16, 500k-reply thread)
Median of 5, newest page of 100. "Rare" is a root with 3 replies.
"Generic" forces `plan_cache_mode = force_generic_plan`.
| | main | this PR |
|---|---|---|
| hot root, custom plan | 2802 ms (513k buffers, 46,750 temp blocks
written) | 1.6 ms (407 buffers) |
| hot root, generic plan | 1779 ms | 0.6 ms |
| rare root, custom plan | 1.2 ms | 0.8 ms |
| rare root, generic plan | 61 ms | 0.08 ms |
Author-filtered reads (`authors:[x], limit:1`) on the hot root: an
author with no reply there takes 1.4 ms on the generic path but 1.7 s on
the route, so author and id selectors stay generic.
On both roots, the PR's SQL returns the same rows as main.
## Tests
-
`e_tag_filter_shape_tests::thread_reply_route_admits_only_single_root_message_reads`
checks which reads take the route. Two roots, mixed kinds, no kinds, no
channel, an uppercase root, a `#p` join, an `exact_match` read, and
`authors`/`pubkey`/`ids` selectors all stay generic. The routed SQL is
checked for the `thread_metadata` walk, the `#e` match and the window
ordering, with no `MATERIALIZED`.
- `postgres_tests::thread_reply_reads_use_thread_metadata` (Postgres
lane) covers:
- mixed 9/40002 replies, a nested reply and a soft-deleted reply,
- a bare-`e` message that the route omits and the generic read (kinds
`[9,40002,7]`) still returns,
- a lone-`root` message, which the route omits too,
- an `exact_match` read, which returns the same rows as the generic
read,
- a nested-parent target, which gets its direct child the generic way,
- root stubs and a legacy parent with no row of its own, checked through
the probe,
- keyset paging,
- no named prepared statement left behind after repeated runs.
-
`handlers::req::tests::postgres_tests::multi_p_thread_filter_keeps_nip01_results`
(Postgres lane) runs a two-value `#p` thread filter through the real
filter-to-query adapter and checks that a bare reference to the root
still comes back.
- `handlers::req::tests::count_fallback_fetches_one_extra_candidate`
checks that COUNT fallbacks set `exact_match`. It is DB-free and was
missing from the `buzz-relay --lib` allowlist, so this PR adds it to
`just test-unit`.
- Mutation-checked: the Postgres test fails if any of these is broken:
- routing disabled,
- persistent statements,
- the nested-target probe dropped,
- stubs treated as all replies or as no replies,
- COUNT allowed to route,
- the deleted filter dropped.
- Blox gate: `cargo fmt`, clippy (`-p buzz-db -p buzz-relay
--all-targets`), buzz-db lib (nextest and plain parallel `cargo test`),
buzz-relay lib, and the buzz-db and buzz-relay Postgres lanes. One
unrelated artifact-sync scale test timed out under load; it passes alone
and in CI.
## What got simpler
- One predicate builder replaces the inline block, so the two read
shapes cannot drift apart.
- One targeted route replaces the planned extra fence variant (a
keys-only `MATERIALIZED` CTE). That variant was dropped because it
reduced the spill but still scanned every reply.
## Identified debt (not in this PR)
- The bridge `page` extension (`crates/buzz-relay/src/api/bridge.rs`,
`extract_page_offset`, built for the kind:0 directory listing) still
maps to SQL `OFFSET`. The routed read honours it too, for parity. Deep
pages there should move to keyset (`until` + `before_id`).
buzz-review-completed
🤖 Generated with [Claude Code](https://claude.com/claude-code)
---------
Signed-off-by: Luke Tornquist <tornquist@squareup.com>
Co-authored-by: Elrond <28d6302a099e5225b02c4155ac4236e4912603df2ab08dbfc2f4fef08ce598c8@buzz.block.builderlab.xyz>
Co-authored-by: Claude Opus 5.5 <noreply@anthropic.com>