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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