huaxingao opened a new pull request #34442:
URL: https://github.com/apache/spark/pull/34442
### What changes were proposed in this pull request?
Add REPEATABLE in SQL syntax TABLESAMPLE so user can specify seed.
### Why are the changes needed?
Current syntax for TABLESAMPLE:
- TABLESAMPLE(x PERCENT)
- TABLESAMPLE(BUCKET x OUT OF y)
`Dataset.sample` has a param to specify seed, so we should allow SQL has a
way to specify seed too.
```
def sample(fraction: Double, seed: Long): Dataset[T] = {
sample(withReplacement = false, fraction = fraction, seed = seed)
}
```
Most of the DBMS uses REPEATABLE to let user specify seed, e.g. DB2, we will
follow the same way.
<img width="1032" alt="Screen Shot 2021-10-29 at 8 46 04 AM"
src="https://user-images.githubusercontent.com/13592258/139465718-285ab5fb-a9cf-4bef-bc32-88301745b12b.png";>
### Does this PR introduce _any_ user-facing change?
Yes
new SQL syntax
- TABLESAMPLE(x PERCENT) REPEATABLE (seed)
- TABLESAMPLE(BUCKET x OUT OF y) REPEATABLE (seed)
### How was this patch tested?
new UT
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