159 lines
4.1 KiB
Elixir
159 lines
4.1 KiB
Elixir
# Pleroma: A lightweight social networking server
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# Copyright © 2017-2020 Pleroma Authors <https://pleroma.social/>
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# SPDX-License-Identifier: AGPL-3.0-only
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defmodule Pleroma.Pagination do
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@moduledoc """
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Implements Mastodon-compatible pagination.
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"""
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import Ecto.Query
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import Ecto.Changeset
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alias Pleroma.Repo
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@default_limit 20
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@max_limit 40
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@page_keys ["max_id", "min_id", "limit", "since_id", "order"]
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def page_keys, do: @page_keys
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def fetch_paginated(query, params, type \\ :keyset, table_binding \\ nil)
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def fetch_paginated(query, %{"total" => true} = params, :keyset, table_binding) do
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total = Repo.aggregate(query, :count, :id)
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%{
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total: total,
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items: fetch_paginated(query, Map.drop(params, ["total"]), :keyset, table_binding)
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}
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end
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def fetch_paginated(query, params, :keyset, table_binding) do
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options = cast_params(params)
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query
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|> paginate(options, :keyset, table_binding)
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|> Repo.all()
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|> enforce_order(options)
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end
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def fetch_paginated(query, %{"total" => true} = params, :offset, table_binding) do
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total =
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query
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|> Ecto.Query.exclude(:left_join)
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|> Repo.aggregate(:count, :id)
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%{
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total: total,
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items: fetch_paginated(query, Map.drop(params, ["total"]), :offset, table_binding)
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}
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end
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def fetch_paginated(query, params, :offset, table_binding) do
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options = cast_params(params)
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query
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|> paginate(options, :offset, table_binding)
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|> Repo.all()
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end
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def paginate(query, options, method \\ :keyset, table_binding \\ nil)
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def paginate(query, options, :keyset, table_binding) do
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query
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|> restrict(:min_id, options, table_binding)
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|> restrict(:since_id, options, table_binding)
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|> restrict(:max_id, options, table_binding)
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|> restrict(:order, options, table_binding)
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|> restrict(:limit, options, table_binding)
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end
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def paginate(query, options, :offset, table_binding) do
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query
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|> restrict(:order, options, table_binding)
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|> restrict(:offset, options, table_binding)
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|> restrict(:limit, options, table_binding)
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end
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defp cast_params(params) do
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param_types = %{
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min_id: :string,
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since_id: :string,
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max_id: :string,
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offset: :integer,
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limit: :integer,
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skip_order: :boolean
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}
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params =
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Enum.reduce(params, %{}, fn
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{key, _value}, acc when is_atom(key) -> Map.drop(acc, [key])
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{key, value}, acc -> Map.put(acc, key, value)
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end)
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changeset = cast({%{}, param_types}, params, Map.keys(param_types))
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changeset.changes
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end
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defp restrict(query, :min_id, %{min_id: min_id}, table_binding) do
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where(query, [{q, table_position(query, table_binding)}], q.id > ^min_id)
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end
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defp restrict(query, :since_id, %{since_id: since_id}, table_binding) do
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where(query, [{q, table_position(query, table_binding)}], q.id > ^since_id)
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end
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defp restrict(query, :max_id, %{max_id: max_id}, table_binding) do
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where(query, [{q, table_position(query, table_binding)}], q.id < ^max_id)
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end
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defp restrict(query, :order, %{skip_order: true}, _), do: query
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defp restrict(query, :order, %{min_id: _}, table_binding) do
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order_by(
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query,
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[{u, table_position(query, table_binding)}],
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fragment("? asc nulls last", u.id)
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)
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end
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defp restrict(query, :order, _options, table_binding) do
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order_by(
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query,
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[{u, table_position(query, table_binding)}],
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fragment("? desc nulls last", u.id)
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)
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end
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defp restrict(query, :offset, %{offset: offset}, _table_binding) do
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offset(query, ^offset)
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end
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defp restrict(query, :limit, options, _table_binding) do
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limit =
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case Map.get(options, :limit, @default_limit) do
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limit when limit < @max_limit -> limit
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_ -> @max_limit
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end
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query
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|> limit(^limit)
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end
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defp restrict(query, _, _, _), do: query
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defp enforce_order(result, %{min_id: _}) do
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result
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|> Enum.reverse()
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end
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defp enforce_order(result, _), do: result
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defp table_position(%Ecto.Query{} = query, binding_name) do
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Map.get(query.aliases, binding_name, 0)
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end
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defp table_position(_, _), do: 0
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end
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