1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
|
# Pleroma: A lightweight social networking server
# Copyright © 2017-2019 Pleroma Authors <https://pleroma.social/>
# SPDX-License-Identifier: AGPL-3.0-only
defmodule Pleroma.Pagination do
@moduledoc """
Implements Mastodon-compatible pagination.
"""
import Ecto.Query
import Ecto.Changeset
alias Pleroma.Repo
@default_limit 20
def fetch_paginated(query, params, type \\ :keyset)
def fetch_paginated(query, %{"total" => true} = params, :keyset) do
total = Repo.aggregate(query, :count, :id)
%{
total: total,
items: fetch_paginated(query, Map.drop(params, ["total"]), :keyset)
}
end
def fetch_paginated(query, params, :keyset) do
options = cast_params(params)
query
|> paginate(options, :keyset)
|> Repo.all()
|> enforce_order(options)
end
def fetch_paginated(query, %{"total" => true} = params, :offset) do
total = Repo.aggregate(query, :count, :id)
%{
total: total,
items: fetch_paginated(query, Map.drop(params, ["total"]), :offset)
}
end
def fetch_paginated(query, params, :offset) do
options = cast_params(params)
query
|> paginate(options, :offset)
|> Repo.all()
end
def paginate(query, options, method \\ :keyset)
def paginate(query, options, :keyset) do
query
|> restrict(:min_id, options)
|> restrict(:since_id, options)
|> restrict(:max_id, options)
|> restrict(:order, options)
|> restrict(:limit, options)
end
def paginate(query, options, :offset) do
query
|> restrict(:order, options)
|> restrict(:offset, options)
|> restrict(:limit, options)
end
defp cast_params(params) do
param_types = %{
min_id: :string,
since_id: :string,
max_id: :string,
offset: :integer,
limit: :integer
}
params =
Enum.reduce(params, %{}, fn
{key, _value}, acc when is_atom(key) -> Map.drop(acc, [key])
{key, value}, acc -> Map.put(acc, key, value)
end)
changeset = cast({%{}, param_types}, params, Map.keys(param_types))
changeset.changes
end
defp restrict(query, :min_id, %{min_id: min_id}) do
where(query, [q], q.id > ^min_id)
end
defp restrict(query, :since_id, %{since_id: since_id}) do
where(query, [q], q.id > ^since_id)
end
defp restrict(query, :max_id, %{max_id: max_id}) do
where(query, [q], q.id < ^max_id)
end
defp restrict(query, :order, %{min_id: _}) do
order_by(query, [u], fragment("? asc nulls last", u.id))
end
defp restrict(query, :order, _options) do
order_by(query, [u], fragment("? desc nulls last", u.id))
end
defp restrict(query, :offset, %{offset: offset}) do
offset(query, ^offset)
end
defp restrict(query, :limit, options) do
limit = Map.get(options, :limit, @default_limit)
query
|> limit(^limit)
end
defp restrict(query, _, _), do: query
defp enforce_order(result, %{min_id: _}) do
result
|> Enum.reverse()
end
defp enforce_order(result, _), do: result
end
|
