# `Masu.Group`
[🔗](https://github.com/hattoriai/masu/blob/v0.1.0/lib/masu/group.ex#L1)

Rows grouped by the values of columns, with totals.

    <.data_grid id="orders" source={Order} repo={Repo} group_by={[:status]}>
      <:col field={:status} type={:enum} />
      <:col field={:customer} />
      <:col field={:total} type={:decimal} aggregate={:sum} />
    </.data_grid>

`group_by` names the columns the rows are grouped by, the first the
outermost. Each group is a row of its own, with its value, how many
rows it has, and the totals of the columns that have an `aggregate`
(see `Masu.Column`); it opens on its groups of the next column, or on
its rows. A person groups by a column from its header menu, and the
grouping is part of their view (`Masu.View`).

A row of totals of the whole query shows at the bottom of a grid with a
column that has an `aggregate`, grouped or not.

The groups are counted and totalled by the source: an Ecto source with
one `GROUP BY` for each level that shows, and reads the rows of an open
group a block at a time, as it reads any rows; a list in the LiveView.
So a million rows in forty groups are forty rows until one opens.

Groups sort by their value; sorting by the grouped column turns their
order, and sorting by a column with an aggregate sorts them by it. The
rows of a group sort as the grid's rows do.

A group row's id is `["masu-group", key, value, ...]`, its path: it is
what `Masu.Test.expand/3` takes to open it.

# `t`

```elixir
@type t() :: %Masu.Group{
  aggregates: %{required(String.t()) =&gt; term()},
  count: non_neg_integer(),
  key: String.t(),
  path: [{String.t(), term()}],
  value: term()
}
```

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*Consult [api-reference.md](api-reference.md) for complete listing*