Batch inserts [MOD-555] (#726)

* Batch a bunch of inserts, but still more to do

* Insert many for clickhouse (+ tests)

* Batch the remaining ones except those requiring deduplication

* Risky dedups

* Bit o cleanup and formatting

* cargo sqlx prepare

* Add test around batch editing project categories

* Add struct to satisfy clippy

* Fix silly mistake that was caught by the tests!

* Leave room for growth in dummy_data

src/database/models/collection_item.rs

@@ -81,19 +81,19 @@ impl Collection {
         .execute(&mut *transaction)
         .await?;
 
-        for project_id in self.projects.iter() {
-            sqlx::query!(
-                "
-                    INSERT INTO collections_mods (collection_id, mod_id)
-                    VALUES ($1, $2)
-                    ON CONFLICT DO NOTHING
-                ",
-                self.id as CollectionId,
-                *project_id as ProjectId,
-            )
-            .execute(&mut *transaction)
-            .await?;
-        }
+        let (collection_ids, project_ids): (Vec<_>, Vec<_>) =
+            self.projects.iter().map(|p| (self.id.0, p.0)).unzip();
+        sqlx::query!(
+            "
+                INSERT INTO collections_mods (collection_id, mod_id)
+                SELECT * FROM UNNEST($1::bigint[], $2::bigint[])
+                ON CONFLICT DO NOTHING
+            ",
+            &collection_ids[..],
+            &project_ids[..],
+        )
+        .execute(&mut *transaction)
+        .await?;
 
         Ok(())
     }