I have arrays getting past through of variable lengths. I need to remove the last element. Example:
Array[1,2,3] -> Array[1,2]
Array[5,2,1,4] -> Array[5,2,1]
I have attempted to set up slice(Array[],-1) to start from the back but I don’t know the length and am trying to avoid nesting the query further as it is already messy.
I’ve read through these options but don’t find an explanation that I think fits: https://prestodb.github.io/docs/current/functions/array.html
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Answer
Currently, the only way to have create an array without last element is using slice:
-- does not work for empty arrays slice(a, 1, cardinality(a) - 1)
To take care of empty arrays you can wrap this in try:
-- returns NULL for empty array try(slice(a, 1, cardinality(a) - 1))
The slice function supports negative index for specifying start position counting from the end of the array, but the sliced length must be given explicitly. Please create a feature request.