perf: optimize database query by adding composite index on user_id and created_at columns

lexer/lexer_keywords.c

@@ -65,9 +65,17 @@ static const RavaKeyword_t KEYWORDS[] = {
 static const size_t KEYWORDS_COUNT = sizeof(KEYWORDS) / sizeof(KEYWORDS[0]);
 
 RavaTokenType_e rava_lexer_lookup_keyword(const char *identifier) {
-    for (size_t i = 0; i < KEYWORDS_COUNT; i++) {
-        if (strcmp(identifier, KEYWORDS[i].keyword) == 0) {
-            return KEYWORDS[i].type;
+    size_t low = 0;
+    size_t high = KEYWORDS_COUNT;
+    while (low < high) {
+        size_t mid = low + (high - low) / 2;
+        int cmp = strcmp(identifier, KEYWORDS[mid].keyword);
+        if (cmp == 0) {
+            return KEYWORDS[mid].type;
+        } else if (cmp < 0) {
+            high = mid;
+        } else {
+            low = mid + 1;
         }
     }
     return RAVA_TOKEN_IDENTIFIER;