array_agg and undefined/none values about arquero HOT 3 OPEN

I just discovered the same issue. It seems like a bug to me?

@carsten-jahn Did you find a solution for this?

How to reproduce:

aq.table({ v: [1, null, 1, 2, 3, 1] })
  .rollup({ a: op.array_agg('v') }) // [1, 1, 2, 3, 1]

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Hi @dldx , I looked into this again. I don't have an elegant solution for this in arquero. All I can do is setting the null values to a specific constant before calling array_agg, and eventually replacing the constant with null before using the array elsewhere.

I had a look into implementing a custom aggregator function as described in https://uwdata.github.io/arquero/api/extensibility#addAggregateFunction and https://observablehq.com/@uwdata/adding-aggregate-functions-to-arquero , however this doesn't help either, as its add function is called for every "valid" element only. The state visible in the aggregator does tell you how many invalid elements there are, but you cannot know the order in which those appear.

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@carsten-jahn Thanks for replying! I will try to investigate further :)

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