perl - DBIx::Class联接产生大量的选择语句

我注意到，当我在DBIx :: Class中的select中进行联接时，会得到大量的SELECT语句。例如，我有一个查询，看起来像：

 my $testSetRs = $db->resultset('Testset')->search(
    {%searchCriteria},
    {
        prefetch  => [
            {
                'ax_group_testsets' => {'ax_group' => 'ax_user_groups'},
            },
            {'ax_user_testsets'  => 'ax_user'},
        ],
        '+columns' => [
            {
                'me.ax_group_testsets.ax_group_id'     => 'ax_group_testsets.ax_group_id',
                'me.ax_group_testsets.ax_group.public' => 'ax_group.public',
                'me.ax_group_testsets.ax_group.name'   => 'ax_group.name',
            },
        ],
        collapse => 1,
        group_by => ['me.ts_id', 'me.ts_name'],
        cache    => 1,
    }
);

产生：

SELECT me.ts_id, me.ts_name
FROM testset me
LEFT JOIN ax_group_testset ax_group_testsets ON ax_group_testsets.ts_id = me.ts_id
LEFT JOIN ax_group ax_group ON ax_group.ax_group_id = ax_group_testsets.ax_group_id
LEFT JOIN ax_user_group ax_user_groups ON ax_user_groups.ax_group_id = ax_group.ax_group_id
LEFT JOIN ax_user_testset ax_user_testsets ON ax_user_testsets.ts_id = me.ts_id
LEFT JOIN ax_user ax_user ON ax_user.ax_user_id = ax_user_testsets.ax_user_id
WHERE ( ( ax_user.ax_user_id = ? OR ax_user_groups.ax_user_id = ? ) )
GROUP BY me.ts_id, me.ts_name: '349', '349'

SELECT me.ax_group_id, ax_group.public, ax_group.name FROM ax_group_testset me  JOIN ax_group ax_group ON ax_group.ax_group_id = me.ax_group_id WHERE ( me.ts_id = ? ): '4476'

SELECT me.ax_group_id, ax_group.public, ax_group.name FROM ax_group_testset me  JOIN ax_group ax_group ON ax_group.ax_group_id = me.ax_group_id WHERE ( me.ts_id = ? ): '4566'

SELECT me.ax_group_id, ax_group.public, ax_group.name FROM ax_group_testset me  JOIN ax_group ax_group ON ax_group.ax_group_id = me.ax_group_id WHERE ( me.ts_id = ? ): '4701'

等等

我想要第一个SELECT。它之后的那些困扰着我。每组有一个（超过40个）。这在我所有的联接上都会发生，并且可以通过正确的查询跳入数百个联接。为什么会生成这么多查询，我该怎么办？

我正在运行Perl ActiveState 5.16和DBIx .08250。

最佳答案

您的答案在于DBIx::Class::Manual::Joining和DBIx::Class::ResultSet文档中所述的prefetch属性。
加

  prefetch   => {'ax_group_testsets' => {'ax_group' => 'ax_user_groups'} },

并且，假设您想要所有三个相关记录列：

  '+columns' => [
          {
             'me.ax_group_testsets.ax_group_id'     => 'ax_group_testsets.ax_group_id',
             'me.ax_group_testsets.ax_group.public' => 'ax_group.public',
             'me.ax_group_testsets.ax_group.name'   => 'ax_group.name',
          },
      ],
   collapse => 1,

查询属性哈希值。

关于perl - DBIx::Class联接产生大量的选择语句，我们在Stack Overflow上找到一个类似的问题：https://stackoverflow.com/questions/22559937/