如何查找查询结果的大小 [英] How to find size of query result

问题描述

  records = Record.select（'y_id，source'）
 .where（：source => source，：y_id => y_id）
 .group（：y_id，：source）
 .having（'count（*）= 1'）
  

如果我 puts记录，我会得到以下输出：<
[＃<记录来源：XYZ，y_id：10000009> ;,＃<记录来源：XYZ，y_id：10000070>]

这看起来像输出数组中有2个元素。但是当我尝试做 records.size 时，我得到：

{[10000009，XYZ] => 1 ，[10000070，XYZ] => 1}

• 当记录是一个有2个元素的数组时，为什么不是 records.size print 2 由于某种原因，组由查询结果的行为有所不同？

b
$ b

解决方案

我可能走错了路，但我认为问题在于以 .size 的方式工作。

尺寸会自动尝试确定是否调用 .count 或 .length 。它们的行为如下所示：

• .count执行SQL COUNT


• .length计算结果数组的长度
  

然而，在事件 .size 中将返回一个散列（因为它已经决定使用 .count ）

所以你的解决方案可能是使用 .length ，它将返回一个整数。

I have the following query in rails:

records = Record.select('y_id, source')
                .where(:source => source, :y_id => y_id)
                .group(:y_id, :source)
                .having('count(*) = 1')

I get the following output if I puts records:
[#<Record source: "XYZ", y_id: 10000009>, #<Record source: "XYZ", y_id: 10000070>]

This looks like there are 2 elements in the output array. But when I try to do records.size I get:
{[10000009, "XYZ"]=>1, [10000070, "XYZ"]=>1}

• Why doesn't records.size print 2 when records is an array having 2 elements? Is the group by query result behaving differently for some reason?

• What should I do to get the size of records

解决方案

I could be on the wrong track but I think the issue is to do with the way .size works.

Size will automatically try to determine whether to call .count or .length. These behave in the followings ways:

• .count performs a SQL COUNT
• .length calculates the length of the resultant array

However on occassion .size will return a hash (as it has decided to use .count)

So your solution may be to use .length which will return an integer.

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