Yngve Kristiansen created ARROW-5274:
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Summary: [Javascript] Wrong array type for countBy
Key: ARROW-5274
URL: https://issues.apache.org/jira/browse/ARROW-5274
Project: Apache Arrow
Issue Type: Bug
Reporter: Yngve Kristiansen
The {{countBy}} function is not returning correct histograms, as it seems to
select the wrong array type for the indexing.
The following line in countBy seems to be causing the problems:
{{const countByteLength = Math.ceil(Math.log(vector.dictionary.length) /
Math.log(256));}}
For example, if the dictionary length is 3, yet the indices length is 1
million, the result of this expression will be 1, which will lead to a
Uint8Array being used, again resulting in overflows.
Codepen example
[https://codepen.io/Yngve92/pen/mYdWrr]
If I switch the expression to: {{const countByteLength =
Math.ceil(Math.log(vector.length) / Math.log(256));}} it seems to be working
all right, but I am not sure if this is correct.
The expression is on L63, L189 in src/compute/dataframe.ts.
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