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Is your feature request related to a problem or challenge? Please describe what you are trying to do.
Today, DataFusion's expression evaluation does not work natively on DictionaryArrays; Instead what happens is that the DictionaryArrays are unpacked into their base type (e.g. a string dictionary gets unpacked into a StringArray)
This is very inefficient, especially for expressions like col != 'foo' -- if col is a DictionaryArray this filter could be applied by finding 'foo' in the dictionary and then checking for values with that dictionary index, and the dictionary could be reused at the output.
alamb
changed the title
Use specialized dictionary compute kernels for binary expr evaluation
Use specialized dictionary compute kernels for binary PhysicalExpr evaluation
Oct 26, 2021
tustvold
added a commit
to tustvold/arrow-datafusion
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this issue
Jun 28, 2022
Is your feature request related to a problem or challenge? Please describe what you are trying to do.
Today, DataFusion's expression evaluation does not work natively on DictionaryArrays; Instead what happens is that the DictionaryArrays are unpacked into their base type (e.g. a string dictionary gets unpacked into a StringArray)
This is very inefficient, especially for expressions like
col != 'foo'
-- ifcol
is aDictionaryArray
this filter could be applied by finding'foo'
in the dictionary and then checking for values with that dictionary index, and the dictionary could be reused at the output.Describe the solution you'd like
When
That probably looks something like:
DictionaryArray
arrow-rs#869Describe alternatives you've considered
Additional context
See #87 for more detail
There are several other operation where dictionary calculation could be much better (e.g. hash aggregate, join, etc)
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