Spurious connections would likely be a massive headache like patterns on the wall matching patterns in the shadows of some random photos taken 2000 miles away while the handwriting style gets matched to a pair of Ukrainian schoolchildren who have never been within 3000 miles while the sentence writing style itself gets matched to an internet post by someone completely unrelated who's never been within 5000 miles talking about potato dishes.

I get that the table is giant but it sounds almost like an expert system which you don't ask questions but rather throw info at and hope it comes back with what you want.

Even bounded these things can be a headache. I've written code that tried to identify duplicate image regions between 2 images and you'd be surprised how many little sections of images that brute force searches can find matches for in others. little areas of sand, particularly generic trees, shapes in clouds, actual duplicated areas which do match but which are rotated through 27 degrees so that you can't do a straight pixel by pixel match or which are slightly more compressed slightly less compressed.

If, for example, your system stores info about links between every image that has the same pattern of stars in it then you'd likely need more storage space than you could get by turning the earth into computronium. Exponentials are a bugger.

You hit the same problem one 1000000x worse if you're trying to match on everything everywhere everywhen.