LiveTable.Transformer (live_table v0.4.0)

Transformers provide complete control over query modification in LiveTable.

Unlike simple filters that add WHERE conditions, transformers receive the full Ecto query and can perform any operations: joins, aggregations, subqueries, GROUP BY, ORDER BY overrides, and complex transformations.

Why Transformers?

Transformers are LiveTable's most powerful feature, enabling:

Complex multi-table filtering that can't be expressed with simple conditions
Dynamic sorting based on user input
Aggregations and computed metrics
Role-based query modifications
Any custom query logic

Basic Usage

def filters do
  [
    sales_filter: Transformer.new("sales_filter", %{
      query_transformer: &apply_sales_filter/2
    })
  ]
end

defp apply_sales_filter(query, filter_data) do
  case filter_data do
    %{"min_sales" => min} when min != "" ->
      from p in query,
        join: s in Sale, on: s.product_id == p.id,
        group_by: p.id,
        having: sum(s.amount) >= ^String.to_integer(min)
    _ ->
      query
  end
end

Transformer Function Signature

Transformer functions receive two arguments and must return a query:

def my_transformer(query, filter_data) do
  # query: The current Ecto query
  # filter_data: Map of applied filter data from URL/form
  # Returns: Modified Ecto query
  query
end

Configuration Options

:query_transformer - Required. Function or {module, function} tuple.
- Function: &my_function/2 or fn query, data -> query end
- MFA: {MyApp.Filters, :transform_query}

State Management

Transformer state persists in URL parameters. Access applied data in templates:

Map.get(@options["filters"], :my_transformer).options.applied_data["field"]