sunchao commented on code in PR #5416:
URL: https://github.com/apache/datafusion-comet/pull/5416#discussion_r3836722894
##########
native/spark-expr/src/string_funcs/split.rs:
##########
@@ -160,9 +213,37 @@ pub fn spark_split_sql(args: &[ColumnarValue]) ->
DataFusionResult<ColumnarValue
_ => return exec_err!("split_sql delimiter must be a string"),
};
- let result = split_sql_string(string.as_ref().unwrap(), delimiter);
- let string_array = GenericStringArray::<i32>::from(result);
- let list_array = create_list_array(Arc::new(string_array));
+ let string = string.clone().unwrap();
+ let mut str_offsets = BufferBuilder::<i32>::new(8);
+ let mut str_values = BufferBuilder::<u8>::new(string.len());
+ str_offsets.append(0);
+
+ if delimiter.is_empty() {
+ for ch in string.chars() {
Review Comment:
[P2] Preserve the whole string for an empty SQL delimiter
`StringSplitSQL` treats an empty delimiter as "do not split", but this
scalar branch now emits one item per character. For a Parquet table `t(s)`
containing `'abc'`, `SELECT split_part((SELECT max(s) FROM t), '', 1) FROM t`
retains the scalar subquery through normal Spark optimization, and Comet's 4.x
route passes its string result to `split_sql` as a scalar. Exact-base/head
native UDF + `ListExtract` probes return `'abc'` versus `'a'` (part `2` changes
from `''` to `'b'`), while Spark 4.0.2 and the unchanged array paths preserve
the whole input. This is the default literal SQL-split route, not the
incompatible-regex opt-in. Please append the whole string once for an empty
delimiter and retain a scalar/array regression test.
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