hanyuzheng7 opened a new pull request, #23161:
URL: https://github.com/apache/flink/pull/23161
## What is the purpose of the change
Implement the array_slice function to extract a subset of elements from an
array.
Returns a subarray of the input array between 'start_offset' and
'end_offset' inclusive.
The offsets are 1-based however 0 is also treated as the beginning of the
array.
Positive values are counted from the beginning of the array while negative
from the end.
If 'end_offset' is omitted then this offset is treated as the length of the
array.
If 'start_offset' is after 'end_offset' or both are out of array bounds an
empty array will be returned.
Returns null if any input is null.
## Brief change log
ARRAY_SLICE for Table API and SQL
Syntax:
`ARRAY_SLICE(array, start_offset[, end_offset])`
Arguments:
array: The array that contains the elements you want to slice.
start_offset: The inclusive starting offset.
end_offset: The inclusive ending offset, this is an optional argument.
Returns:
If 'start_offset' is after 'end_offset' or both are out of array bounds an
empty array will be returned.
Returns null if any input is null.
Examples:
```
SELECT ARRAY_SLICE(['a', 'b', 'c', 'd', 'e'], 1, 3)
Output: [a, b, c]
```
```
SELECT ARRAY_SLICE(['a', 'b', 'c', 'd', 'e'], -1, -3)
Output: []
```
```
SELECT ARRAY_SLICE(['a', 'b', 'c', 'd', 'e'], -3, -1)
Output[c, d, e]
```
```
SELECT ARRAY_SLICE(['a', 'b', 'c', 'd', 'e'], 3, 3)
Output[c]
```
```
SELECT ARRAY_SLICE(['a', 'b', 'c', 'd', 'e'], 1, 30)
Output[a, b,c,d,e]
```
```
SELECT ARRAY_SLICE(['a', 'b', 'c', 'd', 'e'], 1, -30)
Output[]
```
```
SELECT ARRAY_SLICE(['a', 'b', 'c', 'd', 'e'], -30, 30)
Output[a, b, c, d, e]
```
```
SELECT ARRAY_SLICE(['a', 'b', 'c', 'd', 'e'], -30, -5)
Output[a]
```
```
SELECT ARRAY_SLICE(['a', 'b', 'c', 'd', 'e'], 5, 30)
Output[e]
```
```
SELECT ARRAY_SLICE(['a', 'b', NULL, 'd', 'e'], 1, 3)
Output[a, b, null]
```
```
SELECT ARRAY_SLICE(['a', 'b', NULL, 'd', 'e'], 1)
Output[a, b, null, 'd', 'e']
```
```
SELECT ARRAY_SLICE(['a', 'b', NULL, 'd', 'e'], -1)
Output['e']
```
```
SELECT ARRAY_SLICE(['a', 'b', NULL, 'd', 'e'], 0, 0)
Output[a]
```
see also:
spark: https://spark.apache.org/docs/latest/api/sql/index.html#slice
google cloud:
https://cloud.google.com/spanner/docs/reference/standard-sql/array_functions#array_slice
ClickHouse:
https://clickhouse.com/docs/en/sql-reference/functions/array-functions#arrayslice
DockDb: https://duckdb.org/docs/sql/functions/nested#list-functions
## 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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