diff --git a/src/client/src/tscSQLParser.c b/src/client/src/tscSQLParser.c
index b7cc85908c425ed711121b91ccf0835d61a24cb9..da40a6c1567adfb44b1d3c28ae947be86dbc7d9e 100644
--- a/src/client/src/tscSQLParser.c
+++ b/src/client/src/tscSQLParser.c
@@ -7339,18 +7339,19 @@ int32_t setAlterTableInfo(SSqlObj* pSql, struct SSqlInfo* pInfo) {
   bool dbIncluded = false;
 
   SStrToken tmpToken = pAlterSQL->name;
-  tmpToken.z= strndup(pAlterSQL->name.z, pAlterSQL->name.n);
+  char* z0 = strndup(pAlterSQL->name.z, pAlterSQL->name.n);
+  tmpToken.z = z0;
   if (tscValidateName(&tmpToken, true, &dbIncluded) != TSDB_CODE_SUCCESS) {
-    free(tmpToken.z);
+    free(z0);
     return invalidOperationMsg(tscGetErrorMsgPayload(pCmd), msg1);
   }
 
   code = tscSetTableFullName(&pTableMetaInfo->name, &tmpToken, pSql, dbIncluded);
   if (code != TSDB_CODE_SUCCESS) {
-    free(tmpToken.z);
+    free(z0);
     return code;
   }
-  free(tmpToken.z);
+  free(z0);
 
   code = tscGetTableMeta(pSql, pTableMetaInfo);
   if (code != TSDB_CODE_SUCCESS) {
diff --git a/src/util/src/tutil.c b/src/util/src/tutil.c
index 649f8fa5e9697eac76f4a97eb44d5b18e06924ec..7e08178c42cbb7e34a0aec340352916d874a7094 100644
--- a/src/util/src/tutil.c
+++ b/src/util/src/tutil.c
@@ -225,59 +225,66 @@ char *tstrstr(char *src, char *dst, bool ignoreInEsc) {
 }
 
 char* strtolower(char *dst, const char *src) {
-  if (src == NULL || dst == NULL) {
-    return dst;
-  }
-  char* const ret = dst;
-  while (*src) {
-    const char ch = *(src++);
-    *(dst++) = (ch >= 'A' && ch <= 'Z') ? ch - 'A' + 'a' : ch;
-         
-    if (ch == '\'' || ch == '"') {
-      char prev = ch;
-      while (*src) {
-        const char next = *(src++);
-        *(dst++) = next;
-        if (prev != '\\' && next == ch) break;
-        prev = next;
-      }
-    } else if (ch == '`') {
-      while (*src) {
-        const char next = *(src++);
-        *(dst++) = next;
-        if (next == ch) break;
+  int esc = 0;
+  char quote = 0, *p = dst, c;
+
+  assert(dst != NULL);
+
+  for (c = *src++; c; c = *src++) {
+    if (esc) {
+      esc = 0;
+    } else if (quote) {
+      if (c == '\\') {
+        esc = 1;
+      } else if (c == quote) {
+        quote = 0;
       }
+    } else if (c >= 'A' && c <= 'Z') {
+      c -= 'A' - 'a';
+    } else if (c == '\'' || c == '"') {
+      quote = c;
     }
+    *p++ = c;
   }
-  *(dst) = 0;
-  return ret;
+
+  *p = 0;
+  return dst;
 }
 
 char* strntolower(char *dst, const char *src, int32_t n) {
+  int esc = 0, inEsc = 0;
+  char quote = 0, *p = dst, c;
+
   assert(dst != NULL);
-  char* const end = dst + n;
-  while (dst != end) {
-    const char ch = *(src++);
-    *(dst++) = (ch >= 'A' && ch <= 'Z') ? ch - 'A' + 'a' : ch;
-    
-    if (ch == '\'' || ch == '"') {
-      char prev = ch;
-      while (dst != end) {
-        const char next = *(src++);
-        *(dst++) = next;
-        if (prev != '\\' && next == ch) break;
-        prev = next;
+  if (n == 0) {
+    *p = 0;
+    return dst;
+  }
+  for (c = *src++; n-- > 0; c = *src++) {
+    if (esc) {
+      esc = 0;
+    } else if (quote) {
+      if (c == '\\') {
+        esc = 1;
+      } else if (c == quote) {
+        quote = 0;
       }
-    } else if (ch == '`') {
-      while (dst != end) {
-        const char next = *(src++);
-        *(dst++) = next;
-        if (next == ch) break;
+    } else if (inEsc) {
+      if (c == '`') {
+        inEsc = 0;
       }
+    } else if (c >= 'A' && c <= 'Z') {
+      c -= 'A' - 'a';
+    } else if (inEsc == 0 && (c == '\'' || c == '"')) {
+      quote = c;
+    } else if (c == '`' && quote == 0) {
+      inEsc = 1;
     }
+    *p++ = c;
   }
-  *(dst) = 0;
-  return dst - n;
+
+  *p = 0;
+  return dst;
 }
 
 char* strntolower_s(char *dst, const char *src, int32_t n) {