Thanks for your swift reply – very much appreciated.
Unfortunately I had tried
$args[‘posts_per_page’] = 1 already with no noticeable difference between that or, say 3 posts, or 10.
But, having a hit a brick wall it caused me to investigate a few other things and I hit upon the answer…
I realized that for these relationship fields (and it could be up to 4 fields, depending on the layout the user had chosen for the page) I had selected in the “filter” option for the field “search”, “post type” AND “taxonomy” and it crossed my mind that these 12,000 posts would have quite a few terms added – 30,000 in fact! So by turning off the taxonomy filter my problem has been all but eradicated.
There is effectively no performance hit for having 12,000 posts it was the taxonomy filter causing the bottleneck.
Thanks for your help and in this case just making me look harder myself. Hopefully could be useful information for someone else.
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