在Oracle 11.2.0.1.0下dbms_stats.gather_table_stats收集直方图不准

在虚拟机上测评了下MySQL 和 PostgreSQL 的各种LOAD FILE方式以及时间。 因为是虚拟机上的测评，所以时间只做参考，不要太较真, 看看就好了。
MySQL 工具：
    1. 自带mysqlimport工具。
    2. 命令行 load data infile ...
    3. 利用mysql-connector-python Driver来写的脚本。
 PostgreSQL 工具：
    1. pgloader 第三方工具。
    2. 命令行 copy ... from ...
    3. 利用psycopg2写的python 脚本。
测试表结构：

mysql> desc t1;
+----------+-----------+------+-----+-------------------+-------+
| Field    | Type      | Null | Key | Default           | Extra |
+----------+-----------+------+-----+-------------------+-------+
| id       | int(11)   | NO   | PRI | NULL              |       |
| rank     | int(11)   | NO   |     | NULL              |       |
| log_time | timestamp | YES  |     | CURRENT_TIMESTAMP |       |
+----------+-----------+------+-----+-------------------+-------+
3 rows in set (0.00 sec)
mysql> select count(*) from t1;
+----------+
| count(*) |
+----------+
|  1000000 |
+----------+
1 row in set (6.80 sec)

测试CSV文件：
t1.csv

MySQL 自身的loader: （时间24妙）

mysql> load data infile ‘/tmp/t1.csv‘ into table t1 fields terminated by ‘,‘ enclosed by ‘"‘ lines terminated by ‘\r\n‘;
Query OK, 1000000 rows affected (24.21 sec)
Records: 1000000  Deleted: 0  Skipped: 0  Warnings: 0

MySQL python 脚本：（时间23秒）
>>> 
Running 23.289 Seconds

MySQL 自带mysqlimport：（时间23秒）

[[email protected] ~]# time mysqlimport t_girl ‘/tmp/t1.csv‘ --fields-terminated-by=‘,‘ --fields-enclosed-by=‘"‘ --lines-terminated-by=‘\r\n‘ --use-threads=2 -uroot -proot
t_girl.t1: Records: 1000000  Deleted: 0  Skipped: 0  Warnings: 0

real    0m23.664s
user    0m0.016s
sys     0m0.037s

PostgreSQL 自身COPY：（时间7秒）

t_girl=# copy t1 from ‘/tmp/t1.csv‘ with delimiter ‘,‘;
COPY 1000000
Time: 7700.332 ms

Psycopg2 驱动copy_to方法：（时间6秒）

[[email protected] scripts]# python load_data.py
Running 5.969 Seconds.

Pgloader 导入CSV：（时间33秒）

[[email protected] ytt]# pgloader commands.load
                    table name       read   imported     errors            time

                        ytt.t1    1000000    1000000          0         33.514s
------------------------------  ---------  ---------  ---------  --------------
------------------------------  ---------  ---------  ---------  --------------
             Total import time    1000000    1000000          0         33.514s

Pgloader 直接从MySQL 拉数据：（时间51秒）

[[email protected] ytt]# pgloader commands.mysql
                    table name       read   imported     errors            time

               fetch meta data          2          2          0          0.138s
------------------------------  ---------  ---------  ---------  --------------
                            t1    1000000    1000000          0         51.136s
------------------------------  ---------  ---------  ---------  --------------
------------------------------  ---------  ---------  ---------  --------------
------------------------------  ---------  ---------  ---------  --------------
             Total import time    1000000    1000000          0         51.274s

附上commands.load和commands.mysql

commands.load:
LOAD CSV
   FROM ‘/tmp/ytt.csv‘ WITH ENCODING UTF-8
        (
           id, rank, log_time
        )
   INTO postgresql://t_girl:[email protected]:5432/t_girl?ytt.t1
   WITH skip header = 0,
        fields optionally enclosed by ‘"‘,
        fields escaped by backslash-quote,
        fields terminated by ‘,‘  

    SET work_mem to ‘32 MB‘, maintenance_work_mem to ‘64 MB‘; 

commands.mysql:
LOAD DATABASE
     FROM mysql://python_user:[email protected]:3306/t_girl?t1
     INTO postgresql://t_girl:[email protected]:5432/t_girl?ytt.t1

 with data only

  SET maintenance_work_mem to ‘64MB‘,
      work_mem to ‘3MB‘,
      search_path to ‘ytt‘;

附pgloader 手册：
http://pgloader.io/howto/pgloader.1.html

在Oracle 11.2.0.1.0下dbms_stats.gather_table_stats收集直方图不准