improve sql parser performance

src/main/java/com/alibaba/druid/sql/dialect/mysql/parser/MySqlLexer.java

@@ -204,24 +204,18 @@ public class MySqlLexer extends Lexer {
             }
         }
     }
-
+    
     protected final void scanString() {
         {
             boolean hasSpecial = false;
             int startIndex = pos + 1;
-            int endIndex = indexOf('\'', startIndex);
+            int endIndex = text.indexOf('\'', startIndex);
             if (endIndex == -1) {
                 throw new ParserException("unclosed str");
             }
 
             String stringVal = subString(startIndex, endIndex - startIndex);
-            for (int i = 0; i < stringVal.length(); ++i) {
-                char ch = stringVal.charAt(i);
-                if (ch == '\\') {
-                    hasSpecial = true;
-                    break;
-                }
-            }
+            hasSpecial = stringVal.indexOf('\\') != -1;
 
             if (!hasSpecial) {
                 this.stringVal = stringVal;

src/main/java/com/alibaba/druid/sql/parser/Lexer.java

@@ -79,10 +79,6 @@ public class Lexer {
         return text.charAt(index);
     }
     
-    public final int indexOf(char ch, int fromIndex) {
-        return text.indexOf(ch, fromIndex);
-    }
-
     public String addSymbol() {
         return subString(mark, bufPos);
     }
@@ -248,6 +244,11 @@ public class Lexer {
             return;
         }
         
+        if (isFirstIdentifierChar(ch) && ch != 'N') {
+            scanIdentifier();
+            return;
+        }
+        
         nextToken();
     }