From 227ed1bfcca870842b23003cb80690d881406c22 Mon Sep 17 00:00:00 2001
From: Xetera <contact@xetera.dev>
Date: Fri, 10 Apr 2026 19:16:00 +0300
Subject: [PATCH] fix: properly negative cost changes

---
 src/remote/query-optimizer.ts | 28 +++++++++++++---------------
 1 file changed, 13 insertions(+), 15 deletions(-)

diff --git a/src/remote/query-optimizer.ts b/src/remote/query-optimizer.ts
index 8a0dee7..f27e312 100644
--- a/src/remote/query-optimizer.ts
+++ b/src/remote/query-optimizer.ts
@@ -457,15 +457,9 @@ export class QueryOptimizer extends EventEmitter<EventMap> {
     switch (result.kind) {
       case "ok": {
         const indexRecommendations = mapIndexRecommandations(result);
-        const percentageReduction = costDifferencePercentage(
-          result.baseCost,
-          result.finalCost,
-        );
         const indexesUsed = Array.from(result.existingIndexes);
-        const costReductionPercentage = Math.trunc(
-          Math.abs(percentageReduction),
-        );
-        if (costReductionPercentage < MINIMUM_COST_CHANGE_PERCENTAGE) {
+        const reduction = costReductionPercentage(result.baseCost, result.finalCost);
+        if (reduction < MINIMUM_COST_CHANGE_PERCENTAGE) {
           this.onNoImprovements(
             recent,
             result.baseCost,
@@ -484,7 +478,7 @@ export class QueryOptimizer extends EventEmitter<EventMap> {
             state: "improvements_available",
             cost: result.baseCost,
             optimizedCost: result.finalCost,
-            costReductionPercentage,
+            costReductionPercentage: reduction,
             indexRecommendations,
             indexesUsed,
             explainPlan: result.baseExplainPlan,
@@ -558,16 +552,12 @@ export class QueryOptimizer extends EventEmitter<EventMap> {
     const indexRecommendations = Array.from(result.newIndexes)
       .map((n) => result.triedIndexes.get(n))
       .filter((n) => n !== undefined);
-    const percentageReduction = costDifferencePercentage(
-      result.baseCost,
-      result.finalCost,
-    );
-    const costReductionPercentage = Math.trunc(Math.abs(percentageReduction));
+    const reduction = costReductionPercentage(result.baseCost, result.finalCost);
     return {
       state: "improvements_available",
       cost: result.baseCost,
       optimizedCost: result.finalCost,
-      costReductionPercentage,
+      costReductionPercentage: reduction,
       indexRecommendations,
       indexesUsed,
       explainPlan,
@@ -651,3 +641,11 @@ export function costDifferencePercentage(
 ): PercentageDifference {
   return ((newVal - oldVal) / oldVal) * 100;
 }
+
+/**
+ * The % at which cost was reduced. Returns a negative number
+ * if the cost increased
+ */
+export function costReductionPercentage(oldVal: number, newVal: number): number {
+  return Math.trunc(-costDifferencePercentage(oldVal, newVal));
+}