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elixir scrivener handle slow couting example
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| # Paginate | |
| @spec handle_pagination(conn :: Plug.Conn.t(), page :: number | atom, page_size :: number | atom, query :: module) :: | |
| Plug.Conn.t() | |
| defp handle_pagination(conn, page, page_size, query) do | |
| config = %Scrivener.Config{ | |
| module: Repo, | |
| page_number: page, | |
| page_size: page_size, | |
| options: [total_entries: total_entries(query)] | |
| } | |
| query |> Scrivener.paginate(config) | |
| end | |
| # Retrieves the estimated record count | |
| @spec total_entries(query :: module) :: number | |
| defp total_entries(query) do | |
| table_name = table_name(query) | |
| {:ok, result} = | |
| Ecto.Adapters.SQL.query(Repo, "SELECT reltuples::BIGINT AS estimate FROM pg_class WHERE relname=$1", [table_name]) | |
| result.rows |> List.first() |> List.first() | |
| end | |
| # Determines the table name based on a given query | |
| @spec table_name(query :: module) :: module | |
| defp table_name(query) do | |
| module_from_query(query).__schema__(:source) | |
| end | |
| # Retrieves the model module from a given query | |
| @spec module_from_query(module :: module) :: module | |
| defp module_from_query(%{from: {_table, module}}), do: module | |
| defp module_from_query(module), do: module |
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