perf: improve leaderboard mysql query

Author: wa0x6e

src/graphql/operations/leaderboards.ts

@@ -29,7 +29,20 @@ export default async function (parent, args) {
   let orderDirection = (args.orderDirection || 'desc').toUpperCase();
   if (!['ASC', 'DESC'].includes(orderDirection)) orderDirection = 'DESC';
 
-  const orderQuery = uniq([orderBy, ...ORDER_FIELDS])
+  // Use a single extra field for deterministic ordering
+  // depending on the realm (space or user)
+  // This covers 100% of our use cases
+  // Missing realm is coming from queries not used by our UI
+  const orderByFields = [orderBy];
+  if (where['space']) {
+    orderByFields.push('user');
+  } else if (where['user']) {
+    orderByFields.push('space');
+  } else {
+    orderByFields.push('last_vote');
+  }
+
+  const orderQuery = uniq(orderByFields)
     .map((field: string) => `l.${field} ${orderDirection}`)
     .join(', ');