WinkerDu commented on code in PR #2183:
URL: https://github.com/apache/arrow-datafusion/pull/2183#discussion_r846830459
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datafusion/physical-expr/src/expressions/binary.rs:
##########
@@ -430,17 +431,17 @@ fn string_concat(left: ArrayRef, right: ArrayRef) ->
Result<ArrayRef> {
scalar_value => scalar_value.into_array(left.clone().len()),
};
let ignore_null_array =
ignore_null.as_any().downcast_ref::<StringArray>().unwrap();
- let result = (0..ignore_null_array.len())
+ let index_array = (0..ignore_null_array.len())
.into_iter()
.map(|index| {
if left.is_null(index) || right.is_null(index) {
None
} else {
- Some(ignore_null_array.value(index))
+ Some(index as u32)
}
})
- .collect::<StringArray>();
-
+ .collect::<UInt32Array>();
+ let result = take(ignore_null_array, &index_array, None)?;
Review Comment:
@alamb thanks for the advise.
I think we can optimize the whole string concat process to avoid this value
copying, something like:
- original process: build-in `concat` ignoring `NULL` -> generate validity
array or array of indexes -> take valid value from `concat` output array
according to bitmap or indexes
- opmized process: concat two input string array well handled with `NULL`,
no value copy any more.
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