Pavel Stehule <pavel.steh...@gmail.com> writes:
> I seen nice trick based on window function
> http://stackoverflow.com/questions/11700930/how-can-i-trim-a-text-array-in-postgresql

> but isn't it example of wrong evaluation? Result of row_number is not
> correct

Sure it is ... or at least, you won't find anything in the SQL spec that
says it isn't.  The result of a window function is only dependent on the
state of the input, not on SRFs that might happen to be in sibling
SELECT expressions.  (This is one example of why SRFs in SELECT lists
aren't terribly well defined.)

A bigger problem with that query is that there's no guarantee it will
preserve ordering of the elements of the arrays.

                        regards, tom lane

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