In addition to improving efficiency, using metadata is probably the way to deal with the current incompatibility of backlinks with the deaccent option http://bugs.splitbrain.org/?do=details&id=795 (hope I haven't missed this bug being fixed -- in that case all written below is irrelevant).
In short, if you have deaccent>0, actual page names (which are searched for to find backlinks) can have nothing in common with the text in the page source (where links may be in non-Latin alphabet). Therefore backlinks are now useless if you set deaccent to anything non-zero.
As we cannot really find out how a particular page can be referenced to from other pages (there are too many variants with different deaccented symbols), we need to do the other way around: store all pages the current page refereces to (metadata), and then search this information, right?
Denis
[....] also image and backlink references could probably be improved by using metadata.
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