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why did have different result after using partition?
Posted by: zhenxing zhai
Date: December 21, 2005 02:36AM

I hava two tables,record number as follows:

mysql> select count(1) from weblogentry;
+----------+
| count(1) |
+----------+
| 1295377 |
+----------+
1 row in set (0.00 sec)


mysql> select count(1) from rolleruser;
+----------+
| count(1) |
+----------+
| 626007 |
+----------+
1 row in set (0.00 sec)

I make hash partitions to table weblogentry ,new table named weblogentry_new,record number as follow:

mysql> select count(1) from weblogentry_new;
+----------+
| count(1) |
+----------+
| 1295377 |
+----------+
1 row in set (0.00 sec)

now,I have a join query to weblogentry and rolleruser,statment as follows:

select count(1) from weblogentry e,rolleruser u where e.id>((select max(id) from weblogentry)-100000) and e.publishentry='2' and e.ispass=1 and e.userid=u.id order by e.id desc limit 480;

the result is:
mysql> select count(1) from weblogentry e,rolleruser u where e.id>((select max(id) from weblogentry)-100000) and e.publishentry='2' and e.ispass=1 and e.userid=u.id order by e.id desc limit 480;
+----------+
| count(1) |
+----------+
| 269 |
+----------+
1 row in set (0.00 sec)

replace table weblogentry_new ,the result is:
mysql> select count(1) from weblogentry_new e,rolleruser u where e.id>((select max(id) from weblogentry_new)-100000) and e.publishentry='2' and e.ispass=1 and e.userid=u.id order by e.id desc limit 480;
+----------+
| count(1) |
+----------+
| 269 |
+----------+
1 row in set (0.00 sec)

the result is equal,but when I replace count(1) to e.id,e.title,e.publishentry,u.username,u.fullname

the statment become :

select e.id,e.title,e.publishentry,u.username,u.fullname from weblogentry e,rolleruser u where e.id>((select max(id) from weblogentry)-100000) and e.publishentry='2' and e.ispass=1 and e.userid=u.id order by e.id desc limit 480;

mysql> select e.id,e.title,e.publishentry,u.username,u.fullname from weblogentry e,rolleruser u where e.id>((select max(id) from weblogentry)-100000) and e.publishentry='2' and e.ispass=1 and e.userid=u.id order by e.id desc limit 480;
....
269 rows in set (0.01 sec)

the result num is stilll 269,but replace weblogentry to weblogentry_new:

mysql> select e.id,e.title,e.publishentry,u.username,u.fullname from weblogentry_new e,rolleruser u where e.id>((select max(id) from weblogentry_new)-100000) and e.publishentry='2' and e.ispass=1 and e.userid=u.id order by e.id desc limit 480;
.....
66 rows in set (0.00 sec)

the result num becomes 66,why????

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why did have different result after using partition?
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December 21, 2005 02:36AM


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