fix(graphql): make type-filtered objects queries use sane plans

crates/iota-graphql-rpc/src/backward_view/consistent.rs

@@ -33,8 +33,17 @@ pub(crate) fn query(
 /// Returns active objects from `checkpointed_objects` that were consistent
 /// also at the given checkpoint.
 ///
-/// Uses a LEFT JOIN against `objects_backward_history` to exclude objects
-/// that have any entry with `superseded_at_checkpoint > checkpoint_viewed_at`.
+/// Uses a NOT EXISTS subquery against `objects_backward_history` to exclude
+/// objects that have any entry with
+/// `superseded_at_checkpoint > checkpoint_viewed_at`.
+///
+/// # Implementation notes
+///
+/// NOT EXISTS lets Postgres answer "did this object change?" row by row,
+/// with one index lookup each. A LEFT JOIN on a `SELECT DISTINCT` subquery
+/// takes that option away: the full list of changed objects must always be
+/// built first, and in the worst plans it is then also scanned for every
+/// row.
 fn consistent_checkpointed_objects(
     checkpoint_viewed_at: i64,
     page: &Page<Cursor>,
@@ -47,17 +56,19 @@ fn consistent_checkpointed_objects(
         format!("object_status = {ACTIVE}")
     );
 
-    let changed_subquery = query!(format!(
-        "SELECT DISTINCT object_id FROM objects_backward_history \
-         WHERE superseded_at_checkpoint > {checkpoint_viewed_at}"
-    ));
     let mut source = query!(
-        r#"SELECT candidates.* FROM ({}) candidates
-           LEFT JOIN ({}) changed ON candidates.object_id = changed.object_id"#,
-        checkpointed_filtered,
-        changed_subquery
+        "SELECT candidates.* FROM ({}) candidates",
+        checkpointed_filtered
+    );
+    source = filter!(
+        source,
+        format!(
+            "NOT EXISTS (\
+                 SELECT 1 FROM objects_backward_history changed \
+                 WHERE changed.object_id = candidates.object_id \
+                   AND changed.superseded_at_checkpoint > {checkpoint_viewed_at})"
+        )
     );
-    source = filter!(source, "changed.object_id IS NULL");
     page.apply::<StoredBackwardObject>(source)
 }
 

crates/iota-graphql-rpc/src/types/balance.rs

@@ -250,19 +250,20 @@ fn balance_query(
         address,
         coin_type.clone(),
     );
-    let changed = query!(format!(
-        "SELECT DISTINCT object_id FROM objects_backward_history \
-         WHERE superseded_at_checkpoint > {checkpoint_viewed_at}"
-    ));
+    // NOT EXISTS instead of a JOIN; see `consistent_checkpointed_objects`
+    // for explanation.
     let source_a = filter!(
         query!(
-            r#"SELECT candidates.object_id, candidates.coin_balance, candidates.coin_type
-               FROM ({}) candidates
-               LEFT JOIN ({}) changed ON candidates.object_id = changed.object_id"#,
-            checkpointed,
-            changed
+            "SELECT candidates.object_id, candidates.coin_balance, candidates.coin_type \
+             FROM ({}) candidates",
+            checkpointed
         ),
-        "changed.object_id IS NULL"
+        format!(
+            "NOT EXISTS (\
+                 SELECT 1 FROM objects_backward_history changed \
+                 WHERE changed.object_id = candidates.object_id \
+                   AND changed.superseded_at_checkpoint > {checkpoint_viewed_at})"
+        )
     );
 
     let mut history = filter(

crates/iota-indexer/migrations/pg/2026-08-12-120000_backward_view_type_statistics/down.sql

@@ -0,0 +1,6 @@
+-- Restore the default extended-statistics target.
+ALTER STATISTICS checkpointed_objects_type_stats SET STATISTICS -1;
+ALTER STATISTICS objects_backward_history_type_stats SET STATISTICS -1;
+
+ANALYZE checkpointed_objects (object_type, object_type_package, object_type_module, object_type_name);
+ANALYZE objects_backward_history (object_type, object_type_package, object_type_module, object_type_name);

crates/iota-indexer/migrations/pg/2026-08-12-120000_backward_view_type_statistics/up.sql

@@ -0,0 +1,11 @@
+-- Raise the extended-statistics target on the backward-diff tables so all
+-- distinct object types fit in the multi-column MCV list; types outside the
+-- list get a rows=1 estimate, leading to plans that time out.
+ALTER STATISTICS checkpointed_objects_type_stats SET STATISTICS 2500;
+ALTER STATISTICS objects_backward_history_type_stats SET STATISTICS 2500;
+
+-- Rebuild the statistics objects modified above with their new target.
+-- ANALYZE rebuilds them only if all their columns are listed; listing just
+-- those columns keeps the ANALYZE cheap.
+ANALYZE checkpointed_objects (object_type, object_type_package, object_type_module, object_type_name);
+ANALYZE objects_backward_history (object_type, object_type_package, object_type_module, object_type_name);