Is it possible to do this with a rest query + filters? eg.
http://wpsite.com/wp-json/wp/v2/posts?filter[only-permalinks]
Yes, since 4.9.8 (see #43874) it’s possible to render only fields needed with the _fields parameter.
Examples
Render only the permalinks:
https://example.com/wp-json/wp/v2/posts?_fields=link
[
{
link: "https://example.com/foo/"
},
{
link: "https://example.com/bar/"
},
]
Render only the post IDs and permalinks:
https://example.com/wp-json/wp/v2/posts?_fields=id,link
[
{
id: 123,
link: "https://example.com/foo/"
},
{
id: 234,
link: "https://example.com/bar/"
},
]
Render only the post IDs and the slugs:
https://example.com/wp-json/wp/v2/posts?_fields=id,slug
[
{
id: 123,
slug: "foo"
},
{
id: 234,
slug: "bar"
},
]
Fetching All Available Items
Currently we have to fetch all available items with paging, like:
https://example.comwp-json/wp/v2/posts?_fields=slug&per_page=100&page=1
https://example.comwp-json/wp/v2/posts?_fields=slug&per_page=100&page=2
...
where per_page is 10 by default and with maximum value of 100.
Fetching all items in a single request can result in fatal errors if the number of items exceeds the available resources.
The ticket #43998 to allow unbound requests (something like per_page=-1) for logged in users, was closed as wontfix because it doesn’t scale and has performance issues.
There’s a ticket #45140 to increase the upper bound for per_page to few hundreds.
Usually there’s no need to display so many items in a user interface and there exists javascript techniques to handle the pagination.
If more is really needed then one could filter the rest query via rest_{$post_type}_query to override the maximum default value of posts_per_page, at the risk of fatal errors if available resources are exceeded.