truncate 普通表

使用语法：truncate table xx yy zz；

具体例子如下所示：

teledb=# truncate table teledb_pg1;
TRUNCATE TABLE

也可以一次truncate 多个数据表。

teledb=# truncate table t_update, teledb_serial;
TRUNCATE TABLE

truncate 分区表

• 不允许truncate主表

  teledb=# truncate table t_range;
  ERROR:  trancate a partitioned table is forbidden, trancate a partition is allowed
  

  使用语法：truncate xx partition for(x)

  具体例子如下所示：

• truncate 一个时间分区表。

  teledb=# \d+ t_time_range
                                           Table "public.t_time_range"
   Column |            Type             | Collation | Nullable | Default | Storage | Stats target | Description 
  --------+-----------------------------+-----------+----------+---------+---------+--------------+-------------
   f1     | bigint                      |           |          |         | plain   |              | 
   f2     | timestamp without time zone |           |          |         | plain   |              | 
   f3     | bigint                      |           |          |         | plain   |              | 
  Distribute By: SHARD(f1)
  Location Nodes: ALL DATANODES
  Partition By: RANGE(f2)
  	 # Of Partitions: 12
  	 Start With: 2017-09-01
  	 Interval Of Partition: 1 MONTH
  
  teledb=# select * from t_time_range;
   f1 |         f2          | f3  
  ----+---------------------+-----
    1 | 2017-09-01 00:00:00 | 100
    1 | 2017-10-01 00:00:00 | 100
    1 | 2017-11-01 00:00:00 | 100
  (3 rows)
  
  teledb=# truncate t_time_range  partition for  ('2017-09-01' ::timestamp without time zone); 
  TRUNCATE TABLE
  teledb=# select * from t_time_range;
   f1 |         f2          | f3  
  ----+---------------------+-----
    1 | 2017-10-01 00:00:00 | 100
    1 | 2017-11-01 00:00:00 | 100
  (2 rows)
  

• truncate 一个数字分区表。

  teledb=# select * from t_range;
   f1 |             f2             | f3  
  ----+----------------------------+-----
    1 | 2023-08-23 10:29:46.263768 |   1
    2 | 2023-08-23 10:29:46.263768 |  50
    2 | 2023-08-23 10:29:46.263768 | 110
    3 | 2023-08-23 10:29:46.263768 | 100
  (4 rows)
  
  teledb=# \d+ t_range
                                              Table "public.t_range"
   Column |            Type             | Collation | Nullable | Default | Storage | Stats target | Description 
  --------+-----------------------------+-----------+----------+---------+---------+--------------+-------------
   f1     | bigint                      |           |          |         | plain   |              | 
   f2     | timestamp without time zone |           |          | now()   | plain   |              | 
   f3     | integer                     |           |          |         | plain   |              | 
  Distribute By: SHARD(f1)
  Location Nodes: ALL DATANODES
  Partition By: RANGE(f3)
  	 # Of Partitions: 3
  	 Start With: 1
  	 Interval Of Partition: 50
  
  teledb=# truncate t_range  partition for  (1);  
  TRUNCATE TABLE
  teledb=# truncate t_range  partition for  (2);  
  TRUNCATE TABLE
  teledb=# select * from t_range;
   f1 |             f2             |  f3  
  ----+----------------------------+----------------
    2 | 2023-08-23 10:29:46.263768 | 110
    3 | 2023-08-23 10:29:46.263768 | 100
  (2 rows)