I got a surprise when generating an index. Some entries were there, but with missing page numbers.
For example (with … as the ‘following topic’ separator, and comma as the ‘between entries’ separator):
apple … 10, 12
peach … , 11, 14
The first entry above is normal, with two page numbers.
The second, ‘peach’ has the separator, and then a missing page number followed by the ‘between entries’ separator, and then some listed page numbers.
The third entry, ‘pear’, has only the ‘following topic’ separator. Apparently there was one entry (blank) and no more.
After pulling out most of my hair, I finally figured out that these entries were in deleted text, still present in the document but no longer visible in layout view (though visible in the story editor as deleted text). This is a regularly updated looseleaf work on which the authors had recently started working in InCopy, and this was the first issue done with the new work flow. I had intended leaving the changes marked until the job goes to press, in case anyone needed to know who changed what where. Not a good idea.
So, remember, accept all changes in all documents in a book before generating the index.