anew opened a new pull request, #57612:
URL: https://github.com/apache/spark/pull/57612
### What changes were proposed in this pull request?
The `AUTO CDC` command previously required its clauses in a fixed order
after `KEYS (...)`: `APPLY AS DELETE WHEN`, then `SEQUENCE BY`, then `COLUMNS`,
then `STORED AS SCD TYPE`, then `TRACK HISTORY ON`. This relaxes the grammar so
the optional clauses form an unordered set, accepted in any order.
- **Grammar** (`SqlBaseParser.g4`): `autoCdcParameters` now matches the five
clauses as a repeatable alternation `(autoCdcDeleteClause |
autoCdcSequenceByClause | autoCdcColumnsClause | autoCdcStoredAsClause |
autoCdcTrackHistoryClause)*` instead of a fixed positional sequence.
- **`AstBuilder.parseAutoCdcParams`**: reads each clause from the resulting
list; rejects a clause supplied more than once with `DUPLICATE_CLAUSES` via the
shared `checkDuplicateClauses` helper; and enforces the still-mandatory
`SEQUENCE BY` explicitly (the grammar no longer requires it positionally) with
a targeted error.
### Why are the changes needed?
As more AUTO CDC options are added, a fixed clause order is hard for users
to remember. Allowing arbitrary ordering makes the syntax easier to use,
consistent with how other Spark commands (e.g. `CREATE TABLE`) accept their
optional clauses in any order.
### Does this PR introduce _any_ user-facing change?
Yes, a SQL syntax relaxation.
- Before: the AUTO CDC clauses had to be written in one fixed order; any
other order failed with `PARSE_SYNTAX_ERROR`.
- After: the optional clauses may be written in any order. Supplying the
same clause twice now fails with `DUPLICATE_CLAUSES` ("Found duplicate clauses:
<clauseName>."), and omitting the required `SEQUENCE BY` fails with a clear
"AUTO CDC requires a SEQUENCE BY clause." message. Previously valid statements
continue to parse unchanged.
This is a relaxation within the unreleased AUTO CDC feature on master; no
released behavior changes.
### How was this patch tested?
Updated `AutoCdcParserSuite` (67 tests, all passing):
- The former "wrong clause order" negative tests are now positive tests
asserting the clauses parse in the new orders, including one statement with a
fully reversed clause order.
- Added a duplicate-clause rejection test for each of the five clauses
(asserting `DUPLICATE_CLAUSES`).
- Updated the `SEQUENCE BY is required` tests to assert the new targeted
error.
### Was this patch authored or co-authored using generative AI tooling?
Generated-by: Claude Code (Opus 4.8)
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