max / makenotwork

mt: aggregate endorsement counts in the DB for the thread view The thread view streamed every endorsement row (list_endorsements_for_posts) just to count them per post and mark the viewer's own — an unbounded load on an unauthenticated, unthrottled GET, so a hot post's thousands of endorsements loaded on every view. Use a GROUP BY count plus a separate page-bounded query for the viewer's endorsements (only when logged in). The row-level query stays for the callers that genuinely need endorser ids (tests). Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

Author: Max Johnson <me@maxj.phd> · 2026-07-07 15:06 UTC

Commit: 0116a14e5c71f01d1e40358aac4be941b4053fc1

Parent: b8c7acd

4 files changed, +120 insertions, -7 deletions

A multithreaded/.sqlx/query-7a9ba61b2f86825819aba03c7d967ff04423f9436c2d9480c33e26dc93085e55.json +28

		@@ -0,0 +1,28 @@
1	+	{
2	+	"db_name": "PostgreSQL",
3	+	"query": "SELECT post_id, COUNT(*) AS \"count!\"\n FROM post_endorsements\n WHERE post_id = ANY($1)\n GROUP BY post_id",
4	+	"describe": {
5	+	"columns": [
6	+	{
7	+	"ordinal": 0,
8	+	"name": "post_id",
9	+	"type_info": "Uuid"
10	+	},
11	+	{
12	+	"ordinal": 1,
13	+	"name": "count!",
14	+	"type_info": "Int8"
15	+	}
16	+	],
17	+	"parameters": {
18	+	"Left": [
19	+	"UuidArray"
20	+	]
21	+	},
22	+	"nullable": [
23	+	false,
24	+	null
25	+	]
26	+	},
27	+	"hash": "7a9ba61b2f86825819aba03c7d967ff04423f9436c2d9480c33e26dc93085e55"
28	+	}

A multithreaded/.sqlx/query-ef9eaed6231cbd1cad17c68a9c76a26b89a6fea7790348d4fd43c9128c863538.json +23

		@@ -0,0 +1,23 @@
1	+	{
2	+	"db_name": "PostgreSQL",
3	+	"query": "SELECT post_id FROM post_endorsements WHERE post_id = ANY($1) AND endorser_id = $2",
4	+	"describe": {
5	+	"columns": [
6	+	{
7	+	"ordinal": 0,
8	+	"name": "post_id",
9	+	"type_info": "Uuid"
10	+	}
11	+	],
12	+	"parameters": {
13	+	"Left": [
14	+	"UuidArray",
15	+	"Uuid"
16	+	]
17	+	},
18	+	"nullable": [
19	+	false
20	+	]
21	+	},
22	+	"hash": "ef9eaed6231cbd1cad17c68a9c76a26b89a6fea7790348d4fd43c9128c863538"
23	+	}

M multithreaded/crates/mt-db/src/queries.rs +54

			@@ -1267,6 +1267,13 @@ pub struct EndorsementRow {
1267	1267		pub endorser_id: Uuid,
1268	1268		}
1269	1269
	1270	+	/// One post's total endorsement count (from an aggregated `GROUP BY`).
	1271	+	#[derive(sqlx::FromRow)]
	1272	+	pub struct EndorsementCount {
	1273	+	pub post_id: Uuid,
	1274	+	pub count: i64,
	1275	+	}
	1276	+
1270	1277		// ============================================================================
1271	1278		// Tracked thread queries
1272	1279		// ============================================================================
			@@ -1673,6 +1680,12 @@ pub async fn search_threads(
1673	1680		// ============================================================================
1674	1681
1675	1682		/// Batch-fetch endorsements for a set of post IDs.
	1683	+	///
	1684	+	/// Loads one row per endorsement — fine when the caller needs the endorser ids,
	1685	+	/// but the thread view must NOT use this: a hot post with thousands of
	1686	+	/// endorsements would stream every row on every (unauthenticated, unthrottled)
	1687	+	/// page load. That path uses [`count_endorsements_for_posts`] +
	1688	+	/// [`list_user_endorsed_posts`] instead.
1676	1689		#[tracing::instrument(skip_all)]
1677	1690		pub async fn list_endorsements_for_posts(
1678	1691		pool: &PgPool,
			@@ -1687,6 +1700,47 @@ pub async fn list_endorsements_for_posts(
1687	1700		.await
1688	1701		}
1689	1702
	1703	+	/// Per-post endorsement counts, aggregated in Postgres.
	1704	+	///
	1705	+	/// Replaces streaming every endorsement row into the app just to `len()` them:
	1706	+	/// a `GROUP BY` returns at most one row per visible post regardless of how many
	1707	+	/// endorsements a post has (fuzz-2026-07-06 endorsement fan-out). Posts with
	1708	+	/// zero endorsements are absent — the caller defaults them to 0.
	1709	+	#[tracing::instrument(skip_all)]
	1710	+	pub async fn count_endorsements_for_posts(
	1711	+	pool: &PgPool,
	1712	+	post_ids: &[Uuid],
	1713	+	) -> Result<Vec<EndorsementCount>, sqlx::Error> {
	1714	+	sqlx::query_as!(
	1715	+	EndorsementCount,
	1716	+	r#"SELECT post_id, COUNT(*) AS "count!"
	1717	+	FROM post_endorsements
	1718	+	WHERE post_id = ANY($1)
	1719	+	GROUP BY post_id"#,
	1720	+	post_ids,
	1721	+	)
	1722	+	.fetch_all(pool)
	1723	+	.await
	1724	+	}
	1725	+
	1726	+	/// The subset of `post_ids` the given user has endorsed. Bounded by the page's
	1727	+	/// post count (not the endorsement total), so the thread view can mark the
	1728	+	/// viewer's own endorsements without loading every endorser id.
	1729	+	#[tracing::instrument(skip_all)]
	1730	+	pub async fn list_user_endorsed_posts(
	1731	+	pool: &PgPool,
	1732	+	post_ids: &[Uuid],
	1733	+	user_id: Uuid,
	1734	+	) -> Result<Vec<Uuid>, sqlx::Error> {
	1735	+	sqlx::query_scalar!(
	1736	+	"SELECT post_id FROM post_endorsements WHERE post_id = ANY($1) AND endorser_id = $2",
	1737	+	post_ids,
	1738	+	user_id,
	1739	+	)
	1740	+	.fetch_all(pool)
	1741	+	.await
	1742	+	}
	1743	+
1690	1744		// ============================================================================
1691	1745		// Image queries
1692	1746		// ============================================================================

M multithreaded/src/routes/forum/thread.rs +15 -7

			@@ -72,14 +72,16 @@ pub(in crate::routes) async fn thread(
72	72		// this page. They're independent (all keyed off the same post_ids), so run
73	73		// them concurrently rather than as three serial round-trips.
74	74		let post_ids: Vec<uuid::Uuid> = db_posts.iter().map(\|p\| p.id).collect();
75		-	let (all_footnotes, all_endorsements, all_link_previews) = tokio::try_join!(
	75	+	let (all_footnotes, endorsement_totals, all_link_previews) = tokio::try_join!(
76	76		async {
77	77		mt_db::queries::list_footnotes_for_posts(&state.db, &post_ids)
78	78		.await
79	79		.map_err(db_error)
80	80		},
81	81		async {
82		-	mt_db::queries::list_endorsements_for_posts(&state.db, &post_ids)
	82	+	// Aggregate in the DB rather than streaming every endorsement row: a
	83	+	// hot post's thousands of endorsements must not load per page view.
	84	+	mt_db::queries::count_endorsements_for_posts(&state.db, &post_ids)
83	85		.await
84	86		.map_err(db_error)
85	87		},
			@@ -90,13 +92,19 @@ pub(in crate::routes) async fn thread(
90	92		},
91	93		)?;
92	94
93		-	// Group endorsements: counts per post + set of posts current user endorsed
	95	+	// Counts per post from the aggregate; the viewer's own endorsements come from
	96	+	// a separate bounded query (only when logged in) so we never load endorser ids.
94	97		let mut endorsement_counts: HashMap<String, u32> = HashMap::new();
	98	+	for e in &endorsement_totals {
	99	+	endorsement_counts.insert(e.post_id.to_string(), e.count.max(0) as u32);
	100	+	}
95	101		let mut user_endorsed: std::collections::HashSet<String> = std::collections::HashSet::new();
96		-	for e in &all_endorsements {
97		-	*endorsement_counts.entry(e.post_id.to_string()).or_insert(0) += 1;
98		-	if session_user.as_ref().is_some_and(\|u\| u.user_id == e.endorser_id) {
99		-	user_endorsed.insert(e.post_id.to_string());
	102	+	if let Some(u) = session_user.as_ref() {
	103	+	let mine = mt_db::queries::list_user_endorsed_posts(&state.db, &post_ids, u.user_id)
	104	+	.await
	105	+	.map_err(db_error)?;
	106	+	for post_id in mine {
	107	+	user_endorsed.insert(post_id.to_string());
100	108		}
101	109		}
102	110