I do not think that there is any sane way to sort this issue with the amount of posts you have except than setting hierarchical
to false
. Setting hierarchical
to true
has huge impact on performance and aren’t really meant for use in custom post types.
If you do not need a parent/child relationship between posts like the build-in post type page
have, then you should really set hierarchical
to `false. If you really need that relationship, then you are pretty much stuffed unfortunately. With the amount of posts you have I cannot see any viable solution to sort your issue
Just a tip, remember to flush your permalinks after setting hierarchical
to false