title: Hive insert overwrite directory stored as parquet made NULL values
body: <p>I'm trying to add some data in one directory, and after to add these data as partition to a table.</p>
  
  <pre><code>create table test (key int, value int) partitioned by (dt int) stored as parquet location '/user/me/test';
  insert overwrite directory '/user/me/test/dt=1' stored as parquet select 123, 456, 1;
  alter table test add partition (dt=1);
  select * from test;
  </code></pre>
  
  <p>This code sample is simple... but don't work. With the select statement, the output is NULL, NULL, 1. But I need 123, 456, 1.</p>
  
  <p>When I read the data with Impala, I received 123, 456, 1... what is expected.</p>
  
  <p>Why ? What is wrong ?</p>
  
  <p>If I removed the two "stored as parquet", it's all ok... but I want my data in parquet !</p>
  
  <p>PS : I want this construct for a switch of partition, so that when the data are calculated, they don't go to the user...</p>