https://github.com/nfibrokerage/fob
A minimalistic keyset pagination library for Ecto queries
https://github.com/nfibrokerage/fob
cursor ecto keyset library pagination postgresql
Last synced: 3 months ago
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A minimalistic keyset pagination library for Ecto queries
- Host: GitHub
- URL: https://github.com/nfibrokerage/fob
- Owner: NFIBrokerage
- License: apache-2.0
- Created: 2021-02-25T19:27:29.000Z (about 4 years ago)
- Default Branch: main
- Last Pushed: 2024-08-28T15:17:13.000Z (8 months ago)
- Last Synced: 2025-02-06T12:12:05.388Z (3 months ago)
- Topics: cursor, ecto, keyset, library, pagination, postgresql
- Language: Elixir
- Homepage: https://hex.pm/packages/fob
- Size: 102 KB
- Stars: 5
- Watchers: 11
- Forks: 0
- Open Issues: 0
-
Metadata Files:
- Readme: README.md
- Changelog: CHANGELOG.md
- License: LICENSE
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README
# Fob
A minimalistic keyset pagination library for Ecto queries
**N.B.**: you probably don't want to use Fob. Fob makes a number of assumptions
about the queries passed to it, such as:
- each schema will have only one primary key
- each query must be ordered by at least the schema's primary key
- the primary key is always the final ordering condition
- associations are untested and probably do not work
- (left) joins are known to work though
## Usage
Fob works primarily by composing Ecto queries with `Ecto.Query.where/3` and
`Ecto.Query.limit/2`. In general, the tracking of page breaks is left to any
consuming library/application, but Fob provides a convenience tool which it
uses internally for easy testing: `Fob.Cursor`.
A `Fob.Cursor` is a similar idea to a standard elixir `Stream` except that it
does not represent an active connection to a resource (some but not all Elixir
`Stream`s open a process or port and therefore represent a connection to
resource. This disallows some functionality which is desirable for Fob, such
as [`Stream.split/2`](https://github.com/elixir-lang/elixir/issues/2922)).
With the cursor, you may walk through the pages of a dataset with
`Fob.Cursor.next/1` and take multiple pages with `Fob.Cursor.split/2`
```elixir
iex> alias Fob.Cursor
iex> import Ecto.Query, only: [order_by: 2]
iex> cursor = Cursor.new(order_by(MySchema, asc: :id), MyApp.Repo, _initial_pagination = nil, _page_size = 3)
#Fob.Cursor<...>
iex> {_records, cursor} = Cursor.next(cursor)
{[%{id: 1}, %{id: 2}, %{id: 3}], #Fob.Cursor<...>}
iex> {_records, cursor} = Cursor.next(cursor)
{[%{id: 4}, %{id: 5}, %{id: 6}], #Fob.Cursor<...>}
iex> {_records, cursor} = Cursor.split(cursor, 2)
{[%{id: 7}, %{id: 8}, %{id: 9}, %{id: 10}, %{id: 11}, %{id: 12}], #Fob.Cursor<...>}
```
## Why?
Why build an incomplete and minimal keyset pagination
library when there are already workable implementations in
[Paginator](https://github.com/duffelhq/paginator) and
[Quarto](https://github.com/maartenvanvliet/quarto)? Fob was originally cut
out of another library called Haste. In our setup, Haste satisfies all of the
above assumptions.
## Installation
```elixir
def deps do
[
{:fob, "~> 1.0"}
]
end
```
Check out the docs here: https://hexdocs.pm/fob