I'd like to get some traction or feedback on issue #7121 so I know if it's
worth me doing it. What are the objections to:
1. Fixing brittle calculation methods via subqueries?
2. Requiring count(:group=>:author_id) option explicitly when we want a
Hash instead of Fixnum?
Or am I the only one who thinks this is broken? :-(
Andrew Vit
On Tuesday, August 14, 2012 2:13:04 AM UTC-7, Andrew Vit wrote:
>
> For consistency, `relation.count`, `relation.group(:assoc).count`, and
> `relation.to_a.count` should *all* return **Fixnum**s...
>
> In #7121, I opened the discussion about separating `count` into a
> `count_by(:column)` method.
>
> Currently there's a deprecation on `count(:group => :column)`, which
> advises to chain a group relation before calling count. I think this is the
> wrong approach. I suggest either:
>
> 1. Deprecate `count(:group => :col)` in favour of a new `count_by(:col)`
> 2. Accept `count(group: col)` as the only way to get grouped counts.
>
> With the change I'm proposing, either option means any current
> `relation.group(:col).count` would change from returning a Hash to
> returning a Fixnum.
>
> I'd like to look into fixing this when I have some time soon, If you have
> a preference for either of the above directions, let me know.
>
> Andrew Vit
>
>
> On Sunday, August 5, 2012 1:29:55 PM UTC-7, Andrew Vit wrote:
>>
>> I started rails issue #7121, but I think this needs some discussion as
>> it's not just a simple "bug". I might take a stab at it myself, but I'd
>> like to get a blessing or consensus on this:
>>
>> Given a relation:
>>
>> 1. When .group is added for conditions, this forces .count into returning
>> a grouped count instead of a flat numeric count.
>>
>> 2. When .select("virtual_col") and .order("virtual_col") are used, .count
>> fails with a SQL error because the .select is rewritten for COUNT(*) but
>> the .order is still there pointing to a non-existent column.
>>
>> I found a solution for these by wrapping the relation in a subquery. This
>> isolates the relation so calculate doesn't see its group_values and
>> select_values and can't mess them up:
>>
>> def self.wrapped
>> inner_scope = self.all # 3.2: use self.scoped
>> self.unscoped do
>> from(inner_scope.as(table_name))
>> end
>> end
>>
>> Currently I use this by manually wrapping my relation before before
>> calling .count on it: relation.wrapped.count
>>
>> Is there any reason why Relation#calculate shouldn't work this way by
>> default? For grouped counts, here's what I suggest:
>>
>> 1. count() on a relation that uses group_values should just return a
>> numeric count of records, not a hash.
>>
>> 2. grouped counts must be done explicitly: .count(group: "column") or
>> .count_by("column") should return a hash.
>>
>> Currently, finder methods on calculate are deprecated so using
>> .count(group: "column") logs a warning, but with the wrapped method it all
>> works.
>>
>> How to proceed?
>>
>
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