fix: address Copilot review feedback for SchemaStore LRU and prompt constants

- Replace O(n) timestamp scan with O(1) Map insertion order LRU
- Evict in while loop until size <= maxEntries
- Fire schema-change event on eviction for UI consistency
- Rename INDEX_ADVISOR_* constants to QUERY_PERFORMANCE_* to match updated persona

Author: hanhan761

src/commands/llmEnhancedCommands/promptTemplates.ts

@@ -207,14 +207,14 @@ export function setLastPromptSource(source: PromptSource): void {
     lastPromptSource = source;
 }
 
-const INDEX_ADVISOR_ROLE = 'Query Performance Analyst';
+const QUERY_PERFORMANCE_ANALYST_ROLE = 'Query Performance Analyst';
 const QUERY_GENERATOR_ROLE = 'MongoDB Query Generator assistant';
 
-const INDEX_ADVISOR_TASK_FIND =
+const QUERY_PERFORMANCE_TASK_FIND =
     'analyze MongoDB API query performance based on the data provided';
-const INDEX_ADVISOR_TASK_AGGREGATE =
+const QUERY_PERFORMANCE_TASK_AGGREGATE =
     'analyze MongoDB API aggregation pipeline performance based on the data provided';
-const INDEX_ADVISOR_TASK_COUNT =
+const QUERY_PERFORMANCE_TASK_COUNT =
     'analyze MongoDB API count query performance based on the data provided';
 const QUERY_GENERATOR_TASK =
     "generate MongoDB queries based on the user's natural language description and the provided schema information";
@@ -245,9 +245,9 @@ const SINGLE_COLLECTION_QUERY_MESSAGES = [
 ];
 
 export const FIND_QUERY_PROMPT_TEMPLATE = `
-${createPriorityDeclaration(INDEX_ADVISOR_ROLE)}
+${createPriorityDeclaration(QUERY_PERFORMANCE_ANALYST_ROLE)}
 
-${createSecurityInstructions(FIND_QUERY_MESSAGES, INDEX_ADVISOR_TASK_FIND)}
+${createSecurityInstructions(FIND_QUERY_MESSAGES, QUERY_PERFORMANCE_TASK_FIND)}
 
 ## DATA PLACEHOLDERS
 The subsequent user messages will provide the following data that you should use to fill in your analysis:
@@ -396,9 +396,9 @@ ${CRITICAL_JSON_REMINDER}
 `;
 
 export const AGGREGATE_QUERY_PROMPT_TEMPLATE = `
-${createPriorityDeclaration(INDEX_ADVISOR_ROLE)}
+${createPriorityDeclaration(QUERY_PERFORMANCE_ANALYST_ROLE)}
 
-${createSecurityInstructions(AGGREGATE_QUERY_MESSAGES, INDEX_ADVISOR_TASK_AGGREGATE)}
+${createSecurityInstructions(AGGREGATE_QUERY_MESSAGES, QUERY_PERFORMANCE_TASK_AGGREGATE)}
 
 ## DATA PLACEHOLDERS
 The subsequent user messages will provide the following data that you should use to fill in your analysis:
@@ -555,9 +555,9 @@ ${CRITICAL_JSON_REMINDER}
 `;
 
 export const COUNT_QUERY_PROMPT_TEMPLATE = `
-${createPriorityDeclaration(INDEX_ADVISOR_ROLE)}
+${createPriorityDeclaration(QUERY_PERFORMANCE_ANALYST_ROLE)}
 
-${createSecurityInstructions(COUNT_QUERY_MESSAGES, INDEX_ADVISOR_TASK_COUNT)}
+${createSecurityInstructions(COUNT_QUERY_MESSAGES, QUERY_PERFORMANCE_TASK_COUNT)}
 
 ## DATA PLACEHOLDERS
 The subsequent user messages will provide the following data that you should use to fill in your analysis:

src/documentdb/SchemaStore.ts

@@ -88,35 +88,42 @@ export class SchemaStore implements vscode.Disposable {
 
     // ── LRU tracking ──
 
-    /** Mark a key as recently accessed. */
+    /** Mark a key as recently accessed (moves to end of insertion order). */
     private _touchKey(key: string): void {
-        this._accessOrder.set(key, Date.now());
+        this._accessOrder.delete(key);
+        this._accessOrder.set(key, 0);
     }
 
-    /** Evict the least-recently-used entry if over the limit. */
+    /** Evict least-recently-used entries until the store is at or below capacity. */
     private _evictIfNeeded(): void {
-        if (this._analyzers.size <= this._maxEntries) {
-            return;
-        }
-
-        let oldestKey: string | undefined;
-        let oldestTime = Infinity;
-        for (const [key, time] of this._accessOrder) {
-            if (time < oldestTime) {
-                oldestTime = time;
-                oldestKey = key;
+        while (this._analyzers.size > this._maxEntries) {
+            const oldestKey = this._accessOrder.keys().next().value as string | undefined;
+            if (oldestKey !== undefined) {
+                this._analyzers.delete(oldestKey);
+                this._accessOrder.delete(oldestKey);
+                this._evictionCount++;
+                const pending = this._pendingNotifications.get(oldestKey);
+                if (pending !== undefined) {
+                    clearTimeout(pending);
+                    this._pendingNotifications.delete(oldestKey);
+                }
+                // Fire a schema-change event so UI consumers know the schema was removed.
+                const [clusterId, db, coll] = oldestKey.split('::', 3);
+                if (clusterId && db && coll) {
+                    this._onDidChangeSchema.fire({ clusterId, databaseName: db, collectionName: coll });
+                }
+                continue;
             }
-        }
 
-        if (oldestKey !== undefined) {
-            this._analyzers.delete(oldestKey);
-            this._accessOrder.delete(oldestKey);
-            this._evictionCount++;
-            const pending = this._pendingNotifications.get(oldestKey);
-            if (pending !== undefined) {
-                clearTimeout(pending);
-                this._pendingNotifications.delete(oldestKey);
+            // Fallback: _accessOrder may be out of sync with _analyzers.
+            // Pick any entry from _analyzers and register it for future LRU.
+            const fallbackKey = this._analyzers.keys().next().value as string | undefined;
+            if (fallbackKey !== undefined) {
+                this._touchKey(fallbackKey);
+                continue;
             }
+
+            return;
         }
     }