[fix][core] Modify function aliases and remove expr

Author: guojn1

core/src/main/java/org/apache/calcite/sql/SqlUtil.java

@@ -838,6 +838,14 @@ public static String deriveAliasFromOrdinal(int ordinal) {
     return GENERATED_EXPR_ALIAS_PREFIX + ordinal;
   }
 
+  public static String deriveAliasFromSqlNode(SqlNode sqlNode) {
+    if (sqlNode instanceof SqlCharStringLiteral) {
+      return ((SqlCharStringLiteral) sqlNode).toValue();
+    }
+    String deriveAlias = Util.replace(sqlNode.toString(), "`", "");
+    return deriveAlias;
+  }
+
   /**
    * Whether the alias is generated by calcite.
    * @param alias not null

core/src/main/java/org/apache/calcite/sql/validate/SqlValidatorUtil.java

@@ -361,7 +361,11 @@ public static String alias(SqlNode node, int ordinal) {
       if (ordinal < 0) {
         return null;
       } else {
-        return SqlUtil.deriveAliasFromOrdinal(ordinal);
+        String alias = SqlUtil.deriveAliasFromSqlNode(node);
+        if(alias.length()>255){
+          return SqlUtil.deriveAliasFromOrdinal(ordinal);
+        }
+        return alias;
       }
     }
   }