hanyuzheng7 opened a new pull request, #24365:
URL: https://github.com/apache/flink/pull/24365
## What is the purpose of the change
This is an implementation of SPLIT
## Brief change log
Splits a string into an array of substrings based on a delimiter. If the
delimiter is not found, then the original string is returned as the only
element in the array. If the delimiter is empty, then all characters in the
string are split. If either, string or delimiter, are NULL, then a NULL value
is returned.
If the delimiter is found at the beginning or end of the string, or there
are contiguous delimiters, then an empty space is added to the array.
- Syntax
`SPLIT(string, delimiter)`
- Arguments
string: The string need to be split
delimiter: Splits a string into an array of substrings based on a delimiter
- Returns
If the delimiter is not found, then the original string is returned as the
only element in the array. If the delimiter is empty, then all characters in
the string are split. If either, string or delimiter, are NULL, then a NULL
value is returned.
- Examples
```
SELECT SPLIT('abcdefg', 'c');
Result: ['ab', 'defg']
```
- See also
1. ksqlDB Split function
ksqlDB provides a scalar function named SPLIT which splits a string into an
array of substrings based on a delimiter.
Syntax: SPLIT(string, delimiter)
For example: SPLIT('a,b,c', ',') will return ['a', 'b', 'c'].
https://docs.ksqldb.io/en/0.8.1-ksqldb/developer-guide/ksqldb-reference/scalar-functions/#split
2. Apache Hive Split function
Hive offers a function named split which splits a string around a specified
delimiter and returns an array of strings.
Syntax: array<string> split(string str, string pat)
For example: split('a,b,c', ',') will return ["a", "b", "c"].
https://cwiki.apache.org/confluence/display/Hive/LanguageManual+UDF
3. Spark SQL Split function
Spark SQL also offers a function named split, similar to the one in Hive.
Syntax: split(str, pattern[, limit])
Here, limit is an optional parameter to specify the maximum length of the
returned array.
For example: split('oneAtwoBthreeC', '[ABC]', 2) will return ["one",
"twoBthreeC"].
https://spark.apache.org/docs/latest/api/sql/index.html#split
4. Presto Split function
Presto offers a function named split which splits a string around a regular
expression and returns an array of strings.
Syntax: array<varchar> split(string str, string regex)
For example: split('a.b.c', '\.') will return ["a", "b", "c"].
https://prestodb.io/docs/current/functions/string.html
## Verifying this change
This change added tests in CollectionFunctionsITCase.
## Does this pull request potentially affect one of the following parts:
- Dependencies (does it add or upgrade a dependency): (yes / no)
- The public API, i.e., is any changed class annotated with
`@Public(Evolving)`: (yes / no)
- The serializers: (yes / no / don't know)
- The runtime per-record code paths (performance sensitive): (yes / no /
don't know)
- Anything that affects deployment or recovery: JobManager (and its
components), Checkpointing, Kubernetes/Yarn, ZooKeeper: (yes / no / don't know)
- The S3 file system connector: (yes / no / don't know)
## Documentation
- Does this pull request introduce a new feature? (yes / no)
- If yes, how is the feature documented? (not applicable / docs / JavaDocs
/ not documented)
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