整个表更新

Question

目前我们使用MySQL。我们有空间索引表（所以没有InnoDB），并且每x秒执行整个表更新（将对象从一个地方移动到另一个地方）。

目前我们做的：

UPDATE LOW_PRIORITY IGNORE `table` 
SET `column1` = CASE `column2` 
       WHEN 1 THEN ... 
       WHEN 2 THEN ... 
       WHEN 3 THEN ... 
       ... 
       ELSE `column1` 
       END; 

，但它得到的行数增加痛苦万分。是否有更好的方法来完成整个表更新？也许我们应该切换到其他数据库（PostGIS，NoSQL）？

对此有何看法？

Answer 1

一次更新许多行的最好方法是：

• 创建临时表
• 与（主键，新的值）有一个大的INSERT
• 更新表JOIN不是Temptable使用强制它（主键）SET table.oldvalue = temptable.newvalue

更新：

create table test (id integer primary key, p point not null); 
insert into test (id,p) select id, POINT(id%100, floor(id/100)) from serie limit 10000; 
alter table test add spatial index spi (p); 
select id, AsText(p) from test; 

+----+-------------+ 
| id | AsText(p) | 
+----+-------------+ 
| 1 | POINT(1 0) | 
| 2 | POINT(2 0) | 
| 3 | POINT(3 0) | 
... 

| 98 | POINT(98 0) | 
| 99 | POINT(99 0) | 
| 100 | POINT(0 1) | 
| 101 | POINT(1 1) | 
... 

| 9999 | POINT(99 99) | 
| 10000 | POINT(0 100) | 
+-------+--------------+ 


EXPLAIN SELECT id,AsText(p) from test where Contains(GeomFromText('POLYGON((0 0,0 10,10 10,10 0,0 0))'), p); 
+----+-------------+-------+-------+---------------+------+---------+------+------+-------------+ 
| id | select_type | table | type | possible_keys | key | key_len | ref | rows | Extra  | 
+----+-------------+-------+-------+---------------+------+---------+------+------+-------------+ 
| 1 | SIMPLE  | test | range | spi   | spi | 34  | NULL | 112 | Using where | 
+----+-------------+-------+-------+---------------+------+---------+------+------+-------------+ 

create temporary table test2 (id integer primary key, p point not null); 
insert into test2 (id,p) select id, POINT(1+(id%100), 1+floor(id/100)) from serie limit 10000; 
update test, test2 set test.p=test2.p where test.id=test2.id; 

EXPLAIN SELECT id,AsText(p) from test where Contains(GeomFromText('POLYGON((0 0,0 10,10 10,10 0,0 0))'), p); 
+----+-------------+-------+-------+---------------+------+---------+------+------+-------------+ 
| id | select_type | table | type | possible_keys | key | key_len | ref | rows | Extra  | 
+----+-------------+-------+-------+---------------+------+---------+------+------+-------------+ 
| 1 | SIMPLE  | test | range | spi   | spi | 34  | NULL | 102 | Using where | 
+----+-------------+-------+-------+---------------+------+---------+------+------+-------------+ 

这里没问题（MySQL 5.1.41）