On 16/09/14 21:20, Robert Haas wrote:
In practice, I'm not very surprised that the impact doesn't seem too bad when you're running SQL queries from the client. There's so much other overhead, for de-TOASTing and client communication and even just planner and executor costs, that this gets lost in the noise. But think about a PL/pgsql procedure, say, where somebody might loop over all of the elements in array. If those operations go from O(1) to O(n), then the loop goes from O(n) to O(n^2). I will bet you a beverage of your choice that somebody will find that behavior within a year of release and be dismayed by it.
As somebody who did see server melt (quite literally that time unfortunately) thanks to the CPU overhead of operations on varlena arrays +1 (in fact +many).
Especially if we are trying to promote the json improvements in 9.4 as "best of both worlds" kind of thing.
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