如何加快查询执行 MySQL

Question

您必须填写表格表1至1,000,000：

Table view
CREATE TABLE `test` ( `id` INT UNSIGNED NOT NULL AUTO_INCREMENT , `value` INT UNSIGNED NOT NULL , PRIMARY KEY (`id`)) ENGINE = InnoDB;"

我写了一个函数来做这个，但是向表中添加数据太慢了，如何提高插入数据的性能？

function InsertData(){

    global $MySQL;
    for($i = 1; $i != 1000000; $i++){
        $MySQL->query("INSERT INTO `name` (`id`, `value`) VALUES ($i, $i);");
    }

    $MySQL->close();
}

Answer 1

您可以使用事务，以便每千次插入仅提交一次（或者，如果您有勇气，在数百万次查询之后）。这是（勇敢的）示例：

function InsertData(){
   global $MySQL;

   // Start transactions
   $MySQL->query('SET autocommit=0;');
   $MySQL->query('START TRANSACTION;');

   for($i = 1; $i != 1000000; $i++){
      $MySQL->query("INSERT INTO `name` (`id`, `value`) VALUES ($i, $i);");
   }
   // So far, nothing as actually been saved to database
  
   // Commit all inserts.
   $MySQL->query('COMMIT;');
   $MySQL->query('SET autocommit=1;');

   $MySQL->close();
}

如果由于某些 MySQL 限制，这对于单个事务来说太多了，您可以每 10.000 次左右插入执行一次提交：

function InsertData(){
   global $MySQL;

   // Start transactions
   $MySQL->query('SET autocommit=0;');
   $MySQL->query('START TRANSACTION;');

   for($i = 1; $i != 1000000; $i++){
      $MySQL->query("INSERT INTO `name` (`id`, `value`) VALUES ($i, $i);");
      if($i % 10000 == 0) {
         $MySQL->query('COMMIT;');
         $MySQL->query('START TRANSACTION;');
      }
   }
   // So far, nothing as actually been saved to database
  
   // Commit all inserts.
   $MySQL->query('COMMIT;');
   $MySQL->query('SET autocommit=1;');

   $MySQL->close();
}

注意最终限制 -> https://stackoverflow.com/a/2298325/2814721

当然，这是一个实验或一次性脚本。不建议在生产数据库中进行。

Answer 2

如何使用递归 CTE 将逻辑移至数据库？

insert into name (id, value)
with recursive cte as (
    select 1 id
    union all select id + 1 from cte where i < 1000000
)
select id, id from cte

这可能是通过递归一次生成的多行。另一种方法是只生成 10 行，然后将这些行相乘：

insert into name (id, value)
with recursive cte as (
    select 0 id
    union all select id + 1 from cte where i < 9
)
select id, id 
from (
    select 1 + c0.id + c1.id * 10 + c2.id * 100 + c3.id * 1000 + c4.id * 10000 + c5.id * 100000 id
    cte c0
    cross join cte c1
    cross join cte c2
    cross join cte c3
    cross join cte c4
    cross join cte c5
) t

Answer 3

试试这个查询：

INSERT INTO `test` (`id`, `value`) 
SELECT @row := @row + 1 AS row, @row 
FROM (SELECT 0 UNION SELECT 1 UNION SELECT 2 UNION SELECT 3 UNION SELECT 4 UNION SELECT 5 UNION SELECT 6 UNION SELECT 7 UNION SELECT 8 UNION SELECT 9) AS t1,
     (SELECT 0 UNION SELECT 1 UNION SELECT 2 UNION SELECT 3 UNION SELECT 4 UNION SELECT 5 UNION SELECT 6 UNION SELECT 7 UNION SELECT 8 UNION SELECT 9) AS t2, 
     (SELECT 0 UNION SELECT 1 UNION SELECT 2 UNION SELECT 3 UNION SELECT 4 UNION SELECT 5 UNION SELECT 6 UNION SELECT 7 UNION SELECT 8 UNION SELECT 9) AS t3, 
     (SELECT 0 UNION SELECT 1 UNION SELECT 2 UNION SELECT 3 UNION SELECT 4 UNION SELECT 5 UNION SELECT 6 UNION SELECT 7 UNION SELECT 8 UNION SELECT 9) AS t4, 
     (SELECT 0 UNION SELECT 1 UNION SELECT 2 UNION SELECT 3 UNION SELECT 4 UNION SELECT 5 UNION SELECT 6 UNION SELECT 7 UNION SELECT 8 UNION SELECT 9) AS t5, 
     (SELECT 0 UNION SELECT 1 UNION SELECT 2 UNION SELECT 3 UNION SELECT 4 UNION SELECT 5 UNION SELECT 6 UNION SELECT 7 UNION SELECT 8 UNION SELECT 9) AS t6, 
     (SELECT @row:=0) AS nums;

这是一种“插入到...它有效：

1. 表 t1、t2、t3、t4、t5、t6 各有 10 行。交叉加入它们会生成 10^6 = 1000000 个组合，因此结果表将有百万行；
2. 对于每一行，我们选择@row 变量两次。不仅如此，我们还增加了 1；
3. nums表只用于一开始就将变量初始化为0；
4. 将生成的表传递给 INSERT 语句，并将数据存储在表中。

一个看起来更简洁的解决方案是将递归 CTE 与较新的 MySQL/MariaDB 一起使用。我是the one that was submitted by user GMB：

INSERT INTO test (id, value)
WITH RECURSIVE temp AS (
    SELECT 1 AS row
    UNION SELECT row + 1 
    FROM temp
    WHERE row < 1000000
)
SELECT row, row
FROM temp;

根据我的测试，它有点慢。我没有监控内存使用情况。