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perf(feed): replace correlated subqueries with LEFT JOIN aggregations
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Feed queries ran 5 correlated subqueries per row (3 COUNT + 2 EXISTS
for engagement counts and viewer context). Replaced with LEFT JOIN
aggregations computed once per query. Adds migration 016 with indexes
on likes(thought_id), boosts(thought_id), thoughts(in_reply_to_id),
and compound viewer-context indexes — expected to drop ~3s queries to
<100ms on typical page sizes.

Also removes WebFinger from the footer (requires query params, zero
standalone value as a link).
This commit is contained in:
Gabriel Kaszewski
2026-05-29 04:35:32 +02:00
parent fc806f82a4
commit 79f1e63bb8
3 changed files with 38 additions and 24 deletions
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10
crates/adapters/postgres/migrations/016_engagement_indexes.sql Normal file
View File

@@ -0,0 +1,10 @@
-- Indexes for feed engagement counts and sorting.
-- likes and boosts are joined/counted per thought on every feed query.
-- thoughts(in_reply_to_id) is scanned for reply_count.
CREATE INDEX IF NOT EXISTS idx_likes_thought_id ON likes(thought_id);
CREATE INDEX IF NOT EXISTS idx_boosts_thought_id ON boosts(thought_id);
CREATE INDEX IF NOT EXISTS idx_thoughts_in_reply_to_id ON thoughts(in_reply_to_id) WHERE in_reply_to_id IS NOT NULL;
-- Viewer-context lookups: "did I like/boost this?"
CREATE INDEX IF NOT EXISTS idx_likes_user_thought ON likes(user_id, thought_id);
CREATE INDEX IF NOT EXISTS idx_boosts_user_thought ON boosts(user_id, thought_id);

31
crates/adapters/postgres/src/feed/mod.rs
View File

@@ -114,12 +114,19 @@ impl<'a> FeedSqlBuilder<'a> {
}
fn select(&self) -> String {
let viewer_checks = match self.viewer {
Some(uid) => format!(
"EXISTS(SELECT 1 FROM likes WHERE user_id='{uid}' AND thought_id=t.id) AS liked_by_viewer,
EXISTS(SELECT 1 FROM boosts WHERE user_id='{uid}' AND thought_id=t.id) AS boosted_by_viewer"
let (viewer_cols, viewer_joins) = match self.viewer {
Some(uid) => (
"(lv.thought_id IS NOT NULL) AS liked_by_viewer,
(bv.thought_id IS NOT NULL) AS boosted_by_viewer".to_string(),
format!(
"LEFT JOIN (SELECT thought_id FROM likes WHERE user_id='{uid}') lv ON lv.thought_id = t.id
LEFT JOIN (SELECT thought_id FROM boosts WHERE user_id='{uid}') bv ON bv.thought_id = t.id"
),
),
None => (
"false AS liked_by_viewer, false AS boosted_by_viewer".to_string(),
String::new(),
),
None => "false AS liked_by_viewer, false AS boosted_by_viewer".to_string(),
};
format!(
"
@@ -143,13 +150,17 @@ impl<'a> FeedSqlBuilder<'a> {
u.header_url, u.custom_css,
u.local AS author_local,
u.created_at AS author_created_at, u.updated_at AS author_updated_at,
(SELECT COUNT(*) FROM likes l WHERE l.thought_id=t.id) AS like_count,
(SELECT COUNT(*) FROM boosts b WHERE b.thought_id=t.id) AS boost_count,
(SELECT COUNT(*) FROM thoughts r WHERE r.in_reply_to_id=t.id) AS reply_count,
{viewer_checks}
COALESCE(l_agg.cnt, 0) AS like_count,
COALESCE(b_agg.cnt, 0) AS boost_count,
COALESCE(r_agg.cnt, 0) AS reply_count,
{viewer_cols}
FROM thoughts t
JOIN users u ON u.id=t.user_id
LEFT JOIN remote_actors ra ON u.ap_id = ra.url"
LEFT JOIN remote_actors ra ON u.ap_id = ra.url
LEFT JOIN (SELECT thought_id, COUNT(*) AS cnt FROM likes GROUP BY thought_id) l_agg ON l_agg.thought_id = t.id
LEFT JOIN (SELECT thought_id, COUNT(*) AS cnt FROM boosts GROUP BY thought_id) b_agg ON b_agg.thought_id = t.id
LEFT JOIN (SELECT in_reply_to_id, COUNT(*) AS cnt FROM thoughts WHERE in_reply_to_id IS NOT NULL GROUP BY in_reply_to_id) r_agg ON r_agg.in_reply_to_id = t.id
{viewer_joins}"
)
}