Item11326: the code that adds entries to a subscriber set was attempting to optimise the set each time an entry is added. This is a worst-case O(N^2) process, but guarantees a fast lookup when searching for matches in the set. So there's a comromise here; by skipping the optimisation on the read we accept there may be some suboptimal entries. Optimising when a new webnotify is written redresses the balance somewhat.

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